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Crabeater seals are probably the most numerous wild large mammal on earth, they are thinly distributed across a vast area.

Crabeater Seal Basics

Average Weight: 200 - 300 kg / 440 - 660 lb

Average Length: 2.6m - 8.5 ft

Breeding Season: Pups born from September to December, they are weaned at three weeks old at which time they are just acquiring an adult-like fur coat. Females become pregnant again one to weeks after their pup is weaned, it is thought that there is a period of delayed implantation of the foetus as in other similar seals.

Estimated world population: - 11-12 million. Very difficult to gauge the population size as the seals are circumpolar and live in and amongst the pack ice. They are thinly spread over a vast area that is very difficult and expensive to survey requiring ships that are at least ice strengthened and preferably with air support. They are thought to be possibly the most numerous large wild mammals in the world.

Feeding: Not crabs! that was an error made by early sealers who gave them their name. They feed almost entirely on Antarctic krill, Euphausia superba, 95% of their diet is krill, the remained is squid and fish. They have highly adapted teeth which interlock to form a sieve to strain krill out of the water, their Latin name Lobodon means "lobe toothed".

Diving: As Crabeaters feed mainly on krill, they don't have the need to dive so deep or long. A typical dive is around 11 mins and goes to 20-30m though they have been recorded as deep as 430m.

Conservation status: Least concern. Crabeater seals are thought to have increased in number due to the decline of the great baleen whales which resulted in more krill being available for them to eat, though very little is known about historical population sizes. Protected by the Antarctic Treaty and the Convention for the Conservation of Antarctic Seals.

Distribution: Circumpolar, one of the most southerly of all mammals, living in and amongst seasonally drifting pack ice.

Predators: Leopard seals, Killer whales. Leopard seals are thought to be almost entirely responsible for a first year mortality of around 80% of crabeater seal pups. Most crabeater seals carry long deep scars evidencing a close encounter with a Leopard seal as a youngster. If they reach a year old, this threat seems to fall off very significantly.

What are Crabeater Seals like?

These are crabeater seals, probably the most numerous large mammals on earth after humans. The ones in the picture to the right are resting on a large ice floe floating in broken summer ice near the Antarctic peninsula. They are the amongst the most gregarious of seals, even so it is unusual to see many crabeater seals together as they live almost their entire lives on and amongst floating ice, they only form small loose associations. For this reason also, it is difficult to estimate their numbers, estimates vary from around 10million up to 50 million, none with a very high degree of confidence.

Crabeaters are large seals typically of about 220kg (484lb). They are fairly solitary, and the males and females are about the same size as the males do not need to be large to compete for a harem of females as in elephant and fur seals. Even when the females give birth, they are rarely near to other females.

The female gives birth on an ice floe around September and suckles the young from a birth weight of about 20kg (44lb) to 110kg (242lb) at weaning, this takes around a month. As with other Antarctic seals, the female comes into oestrous very quickly and an attendant male will mate with a female, seeing others off. After mating the male leaves the female and goes to find another receptive female that he can mate with.

Many seals give the impression that they form cosy family groups as they lay around together. The reality is usually that it is a mixed group of individuals with no real bonds other than between mothers and their own pups if present. Crabeaters are the most timid of the commonly encountered Antarctic seals, whereas most types of Antarctic seal will lay there pretty much oblivious to what's going on around them, Crabeaters tend to be more alert and are less easy to approach even if on an ice floe, they will quickly display signs of nervousness and are inclined to slip into the water and swim away.

Why are they so often marked along their sides?

Most Crabeater seals, around 80%, have scars on their bodies. These are thought to come from attacks by Leopard Seals in their first year of life. 80% of Crabeaters don't make it it past their first birthday, predation by Leopard Seals is the main reason for this. If they can make it to their first birthday, then the risk drops off very dramatically, possibly because at this time, there are newer, slower pups around and they are getting stronger and faster swimmers by then.

Killer whales are also predators of crabeater seals which will try to evade them by leaving the water and seeking refuge on an ice floe, the highly intelligent killer whales will sometimes work together to break the flow or wash the seal back off and into the sea.

Do crabeater seals eat crabs?

No. Crabeater seals probably got their name because of a mistake by the early sealers who went down to the Antarctic. They actually eat krill, the staple diet of much of Antarctica's bird and mammal population. There are very few crabs or any other Decapod Crustaceans such as lobsters in Antarctic waters. What there are tend to live in very deep water and are limited in distribution.

Individual crabeater seal teeth.

Crabeater seals are uniquely adapted amongst seals in that their teeth are adapted to form a sieve in a similar manner to the baleen plates of the great whales. They take a mouthful of seawater and krill and expel the water through gaps in their teeth while the parts that overlap prevent the krill from escaping.

Each seal consumes about 20kg of krill per day, and a quick bit of maths calculates that between them, Crabeaters eat hundreds of thousands of tonnes of krill per day, that's an awful lot of little shrimps.

They are circumpolar living all around the edge of the Antarctic continent generally following the seasonally variable edge of loose pack ice. They can be found using narrow tide cracks to breathe at while hunting beneath the ice for krill as these two in the picture to the right are.

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Crabeater seals are probably the most numerous wild large mammal on earth, they are thinly distributed across a vast area. Crabeater Seal Basics Average Weight: 200 - 300 kg / 440 - 660 lb Average Length: 2.6m - 8.5 ft Breeding Season: Pups born from September to December, they are weaned at three weeks old at which time they are just acquiring an adult-like fur coat.

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Northern elephant seal, male and female (Mirounga angustirostris), Gulf of the Farallones National Marine Sanctuary (California). Photo: National Oceanic and Atmospheric Administration

(PhysOrg.com) -- A new study may have solved the long-standing question of how elephants sleep during their long migrations at sea, when they can be away from land for up to eight months.

Whales and dolphins are believed to be able to sleep at the surface by having one hemisphere of their brains asleep while the other remains awake, but northern elephant seals ( Mirounga angustirostris) cannot do the same, and they rarely spend much time at the surface. Scientists have therefore wondered how these animals can sleep during their migrations from the Californian breeding colonies to feeding areas around Alaska and the mid-Pacific. Now a new study suggests they may sleep underwater as they slowly sink.

The team of researchers from the US and Japan fitted six young northern elephant seals from the seal colony at the A?o Nuevo State Reserve in California with data loggers. The instruments recorded the speed, depth, temperature, location and three-dimensional movements of the seals and allowed the scientists to model their dives in three dimensions. The seals were released up to 70 km from their colony and then tracked as they made their way back home.

The results of the study showed the seals made the same kind of repetitive deep dives as they are known to make during their migrations. They also found the seals sometimes roll over and then spiral down towards the bottom of the sea in a slow descent known as the drift dive.

According to Russel Andrews, one of the authors of the paper, the periodic wobbling associated with the drift dive resembles the fluttering of a leaf falling to the ground, and slows down the rate of descent. The scientists believe the seals use the long dive to rest, process their food, and possibly even sleep. The depth of the dive (800 m or more for males and 600 m for females) also reduces the risk of attack by predators.

The northern elephant seal migrates twice a year between the breeding colonies in California and Mexico and feeding grounds in the north Pacific. The males head for the Gulf of Alaska and the Aleutian Islands, while the feeding grounds used by adult females are further south. Elephant seals are the only animals that migrate biannually, and they spend between 250 and 300 days a year at sea, and travel up to 21,000 km.

The paper was published in the Royal Society's Biology Letters.

© 2009 PhysOrg.com

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(PhysOrg.com) -- A new study may have solved the long-standing question of how elephants sleep during their long migrations at sea, when they can be away from land for up to eight months.

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You can't see them to count them, but Amazonian manatees seem to be recovering

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Diogo de Souza used to wake up at 3 a.m., stop by the house of a community member who knew about manatees, and the two began work among the carapanãs, the large Amazonian mosquitoes, as the sun came up. Sitting still in their wooden canoe under the scorching sun typical of the dry season, they [...]

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We have something to tell you about a creature with a horn. Unicorns do exist! Yes, the mythical creature does exist, but to find it in the forest like cartoons tell us might be a little bit difficult. At least, we can already find in the ocean. Meet the unicorns of the ocean, narwhals.

Narwhals are called as the unicorns of the ocean because of their unique feature. Just like how unicorns are depicted, a horse with a horn on its head, narwhals appear like small whale with a long horn on their head. But what's actually the function of the horn?

Researchers have long tried to find out the real function of the horn. And based on their assumptions, many researchers came up with estimations either it is used as self-defense, sensory organ, or to attract mate from the opposite sex.

Those estimations have now come to the truth. Which one is the true nature? Recently, researchers finally found out the real truth.

The Origin Of Narwhal's Horn

Have you ever seen a narwhal? What a unique creature it is with its horn. The horn appears like a long bone growing right at the center of its head. But don't you know that the thing we are talking about is literally growing from inside of its head?

The horn of narwhal is actually an exaggerated front tooth of the male animal. It protrudes outside from its mouth as the cetacean grows older. What's interesting is, the horn will keep on growing until the cetacean dies.

This is the reason why some narwhals can grow a horn up to three meters long. But there is something more peculiar in this case. The horn is actually the exaggeration of its left front tooth only, while the right front tooth remains short like normal tooth.

The horn itself is not like elephant tusk, which is dense inside and outside. Narwhal's horn is very hard outside, but the inside of the horn is actually soft. This is the opposite of most animals' teeth composition that's usually soft on the outside and harder on the inside.

"No big surprise. It's been opposite in every other way. But to find a tooth that is soft on the outside and has its most dense part around the pulp was completely odd," clinical instructor at the Harvard School of Dental Medicine, Martin Nweeia.

A Sensory Horn?

Martin Nweeia is one of the researchers who studied the horn. The researcher conducted a research by testing whether the horn can sense external stimuli like water pressure, temperature, and salinity. The reason for this study was to learn whether the horn could sense something.

The horn, which Nweeia mentioned as a tusk "essentially built inside out", is full of nerves inside, and the texture is very porous. "This tooth is almost like a piece of skin in the sense that it has all these sensory nerve endings," Nweeia told BBC Earth in an interview.

The research was done by capturing several individuals and anchored them to the shore using a net. Their horns were then being encased in special 'jacket' that can give external stimuli mentioned above, while heart rate sensors were placed on their bodies.

With external stimuli to their horn, Nweeia discovered that narwhals could sense changes. It was proven with changing heartrate of the animal to different stimuli to the horn. But is it a sensory organ? Well, the researcher still couldn't draw any conclusion from that.

Female narwhals don't grow horn, yet they can live to the fullest as good as the male with horn. "But regardless of the reason, the results suggest that narwhals can funnel water into their tusks to measure its salt concentration," Nweeia said.

A Way To Show Off?

So, narwhal's horn might be proven to be able to sense outside stimuli. But another research conducted by Zackary Graham from Arizona State University, whose study was published in the journal Biology Letters, might found another use of it.

"Broadly, I'm interested in sexual selection, which is responsible for creating some of the craziest traits in biology. As an evolutionary biologist, I try to understand why some animals have these bizarre traits, and why some don't," the researcher said.

Graham's study found that the horn might also work as a way to show off between individuals. He and his team examined data collected from 245 adult male narwhals and found out that only the biggest and strongest ones can grow extra-long horns.

"The information that the tusk communicates is simple: 'I am bigger than you," said Graham. Most likely, the reason is because alpha males and the strongest ones can access more nutrients either by physical competition or seer intimidation.

Furthermore, with longer horns, the strongest ones can show off to their opposite sex and tell them that they are among 'the best males' in the group. "We also predicted that if the narwhal tusk is sexually selected, we expect greater variation in tusk length compared to the variation in fluke width," Graham explained.

A Horn As Weapon?

Funnily, there is also a possibility that the horn is actually a real weapon. A video footage recorded in Canada shows how the cetacean used its horn to stun fish. The video showed a narwhal striking arctic cod before eating it. Just Like California, Arctic Is Burning Too Because Of Climate Change

"Kind of tracking the cod with the tusk, and as the cod was positioned close to the tip of the tusk, the narwhal sort of gave it a quick, hard tap that likely stunned the fish. It looked like it was momentarily not moving, and then the narwhal would move in with its mouth and suck in the prey," Steve Ferguson of Fisheries and Oceans Canada explained.

In conclusion, all of the assumptions made by researchers about the real use of narwhal's horn or tusk is right. It can sense things, it can show dominance and attract opposite sex, it can also be used as a weapon to hunt for food.

But why did it take so long for researchers to find out the truth? There is one good reason for that, because narwhals are highly elusive. In fact, there is not a single individual is currently being able to be brought into captivity.

Researchers usually study a species after bringing it into captivity for accessibility reason, but narwhals are too elusive for that. Thanks to advancement of technology nowadays, we can finally find the truth behind narwhal's horn.

Sources:
https://www.treehugger.com/ https://edition.cnn.com/ https://ocean.si.edu/ https://oceanconservancy.org/

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Why Narwhals Grow Horn? Researchers Finally Discovered The Reasons

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We have something to tell you about a creature with a horn. Unicorns do exist! Yes, the mythical creature does exist, but to find it in the forest like cartoons tell us might be a little bit difficult. At least, we can already find in the ocean.

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Geographic Range

Northern right whale dolphins (Lissodelphis borealis) are endemic to the waters of the North Pacific Ocean. On the eastern coast of Asia, they are found from Paramushir Island, Russia to Cape Nojima, Japan. On the western coast of North America, they have been documented from Vancouver Island, Canada to Baja California, Mexico. Multiple entanglements in high seas driftnets confirmed their presence across the North Pacific Ocean. A few sightings have occurred outside their typical range including the Gulf of Alaska and near the Aleutian Islands. ( Bjorge, et al., 1992; Jefferson and Newcomer, 1993; Kajimura and Loughlin, 1988; Leatherwood and Walker, 1979; Nishiwaki, 1967)

Habitat

Northern right whale dolphins most commonly inhabit deep offshore and continental waters. However, they are occasionally observed near the coast, particularly where undersea geographic features create deep waters close to shore. They prefer cool waters, and are most often sighted in waters ranging in temperature from to 7.8° to 18.9° C. ( Bjorge, et al., 1992; Jefferson and Newcomer, 1993; Jefferson, et al., 1994a; Leatherwood and Walker, 1979)

This species has been documented migrating south and inshore during the winter months, and north and offshore during the summer months. Within their eastern range, specifically California, they are sighted inshore in the fall months; they increase in numbers until mid-winter, and then decrease towards the late spring and early summer. In their western range, off the coast of northern Honshu, Japan, northern right whale dolphins have only been reported during non-summer months. The reasons for these seasonal movements are largely unknown; however, changes in water temperature could be a factor. In the fall, northern right whale dolphins move toward the cooling waters of the California coast and withdraw in the spring/summer as they warm. Another possible influence could be prey abundance. In California, the maximum abundance of northern right whale dolphins correlates with the maximum abundance of an important prey item, ( California market squid. Forney and Barlow, 1998; Jefferson and Newcomer, 1993; Kasuya, 1971; Leatherwood and Walker, 1979)

Physical Description

Northern right whale dolphins have a mostly black body. However, they possess a white stripe that begins at their throat, widens in the thoracic region and continues as a thin band that terminates at the fluke notch. Compared to males, females have wider white markings around their urogenital region. Both males and females possess a white mark behind the tip of their lower jaw. The dorsal side of their flukes are predominantly light grey and primarily white on the ventral side. Variation in color does occur, typically in the area covered by the white ventral markings. Some common variations from the normal coloration include the white ventral strip extending up the edges of the body, white coloration of nearly the whole lower jaw, a white smudge on the side of the melon and beak and variation in the amount of white coloration on the flippers. ( Baird and Stacey, 1991; Baird and Stacey, 1993; Jefferson and Newcomer, 1993; Jefferson, et al., 1994a; Jefferson, et al., 1994b; Leatherwood and Walker, 1979; Okada and Hanaoka, 1940)

A peculiar feature of northern right whale dolphins is their lack of a dorsal fin; they are the only dolphin species in the North Pacific Ocean without one. Another diagnostic characteristic of this species is its slender, elongated caudal peduncle. They possess a straight mouth line and a short, yet distinct beak. Their flippers are slightly curved with pointed tips. Their flukes possess a concave posterior margin and a deep central notch. Both their flippers and flukes look disproportionately small compared to their body. Overall, they possess a very streamlined shape. ( Baird and Stacey, 1993; Jefferson and Newcomer, 1993; Jefferson, et al., 1994a; Jefferson, et al., 1994b; Leatherwood and Walker, 1979)

Their maximum known weight is 115 kg. The mean length of males aged 12 and older is 237.9 cm, while the largest male measured was 307.0 cm long. The mean length of females aged 12 or older is 211.2 cm. No females over 230 cm have been collected. Males appear to reach greater maximum lengths than females. ( Ferrero and Walker, 1993; Jefferson and Newcomer, 1993; Jefferson, et al., 1994b; Leatherwood and Walker, 1979)

Their teeth are cone shaped, small, slender and sharp. There is great variation in the dental formula and number of teeth possessed by individuals of this species. Each side of the upper jaw holds 37 to 52 teeth, with 42 to 54 teeth on each side of the lower jaw. They can have 158 to 212 teeth total. ( Baird and Stacey, 1991; Baird and Stacey, 1993; Jefferson and Newcomer, 1993; Jefferson, et al., 1994a; Jefferson, et al., 1994b; Leatherwood and Walker, 1979; Okada and Hanaoka, 1940)

Calves achieve their adult colorations at approximately one year. Before this, they are a paler version of the adult coloration, consisting predominantly of browns, greys and creams. ( Baird and Stacey, 1991; Jefferson and Newcomer, 1993; Leatherwood and Walker, 1979)

male larger

sexes colored or patterned differently

Range mass

115 (high) kg

253.30 (high) lb

Range length

307 (high) cm

120.87 (high) in

Reproduction

Currently, nothing is known about the mating system of northern right whale dolphins.

Little is known about the reproduction of northern right whale dolphins. The minimum calving interval is estimated to be two years, because their gestation period is estimated at over 12 months and because of the lack of ovarian activity in a sample of females who were presumed to have given birth at least one year prior. Their gestation period is estimated to be 12.1 to 12.3 months. Calving appears to peak in July and August. Ferrero and Walker (1993) calculated mean lengths at birth to be 99.7 to 103.8 cm. The duration of lactation remains unknown. The average age of sexual maturity for females is estimated to be 9.7 to 10.4 years, when their body length is approximately 199.8 to 201.1 cm. The average age of sexual maturity among males is estimated to be 9.9 to 10.1 years. Testis mass changes little with age until the onset of sexual maturity, when it then increases rapidly. Mature testis masses range from 117.4 to 1,300 g. ( Ferrero and Walker, 1993)

Breeding interval

There is likely at least 2 years between each calving event.

Breeding season

Since northern right whale dolphins have about a 12 month gestation period and many calves are born in July and August, their breeding season is likely around the same time seasonally.

Average gestation period

12.1 to 12.3 months

Average age at sexual or reproductive maturity (female)

9.7 or 10.4 years

Average age at sexual or reproductive maturity (male)

9.9 or 10.1 years

Currently, nothing is known about the parental investment of northern right whale dolphins.

Lifespan/Longevity

There is very little information available regarding the lifespan of northern right whale dolphins. However, the live-capture fishery has taken two live specimens. One died three days after its introduction into an acclimation pool. The autopsy and histopathology examinations determined the cause of death was linked to stress. The second lived 15 months in a 540,000 gallon display tank. The cause of death for this individual was never determined. ( Walker, 1975)

Behavior

Northern right whale dolphins are very social. Off the eastern Pacific coast, the average pod size is 110 individuals, while off the western Pacific coast, they have an average pod size of 200 individuals. They have also been periodically observed alone. ( Jefferson and Newcomer, 1993; Jefferson, et al., 1994a; Leatherwood and Walker, 1979)

Individuals swimming slowly generally only expose small portions of their head, mainly the blowhole, to breath. Fast swimming individuals may either swim close to the surface, surfacing rapidly to breathe or swim swiftly at the surface with low angle leaps. Northern right whale dolphins have also been seen performing belly flops, fluke slaps and side slaps. Individuals have been observed breathing at intervals of 10 to 75 seconds, and entire pods have been noted to dive for a maximum of 6.15 minutes. They have been reported to swim at speeds up to 34 km per hour. ( Au and Weihs, 1980; Jefferson, et al., 1994a; Leatherwood and Walker, 1979)

Northern right whale dolphins generally occur in one of four different pod configurations. The first configuration is densely packed groups lacking distinct subgroups. The second consists of noticeably distinct subgroups of varying numbers of individuals. Third, is a v-shaped formation and fourth is a line formation. When northern right whale dolphins are in the company of other ( cetacean species, they typically maintain small, tightly packed groups. They will, however, form mixed interspecific pods with Pacific white-sided dolphins. Jefferson, et al., 1994a; Leatherwood and Walker, 1979)

This species exhibits remarkably variable behavior towards boats. They may vigorously avoid them or they may approach and interact with them. Bow riding more readily occurs in the presence of other cetacean species, such as Pacific white-sided dolphins. ( Jefferson and Newcomer, 1993; Jefferson, et al., 1994a; Leatherwood and Walker, 1979)

Northern right whale dolphins are frequently documented interacting with other marine mammal species. They are most commonly associated with Pacific white-sided dolphins; they have also been seen with common bottlenose dolphins, ( short-beaked common dolphins, striped dolphins, Risso's dolphins, Dall's porpoises, short-finned pilot whales, fin whales, sei whales, humpback whales, grey whales and California sea lions. Baird and Stacey, 1991; Baird and Stacey, 1993; Ferrero, et al., 2002; Jefferson, et al., 1994a; Leatherwood and Walker, 1979; Leatherwood, 1974; Wilke, et al., 1953)

All documented strandings have been of single individuals, and no mass strandings have been ever reported. Typically, only a few individual strandings occur each year. The exception was in 1981, where approximately 23 northern right whale dolphins were stranded on southern and central California beaches for undetermined reasons. Strandings have been mainly linked with pathological conditions caused, or irritated by parasites. ( Baird and Stacey, 1991; Cowan, et al., 1986; Jefferson and Newcomer, 1993; Leatherwood and Walker, 1979)

Home Range

There is currently no information available regarding the home range size of northern right whale dolphins.

Communication and Perception

Northern right whale dolphins primarily communicate with clicks and pulsed vocalizations. Unlike other dolphin species, they do not produce whistles. A commonly produced sound is a burst-pulse series. Burst-pulse series consist of 6 to 18 individual burst-pulse units. Eight unique burst-pulse series have been documented, and most series are repeated in sequence. Compared to echolocation clicks, burst-pulse vocalizations are lower in frequency and shorter in duration. It is believed that these burst-pulse vocalizations may play a comparable role in communication to the conventional whistles emitted by other ( delphinid species. Rankin, et al., 2007)

Food Habits

Northern right whale dolphins prey primarily on mesopelagic fish and squid. They dive to depths of at least 200 m in search of food. ( Chou, et al., 1995; Jefferson and Newcomer, 1993; Chou, et al., 1995; Fitch and Brownell, 1968; Jefferson and Newcomer, 1993)

Chou, Bright and Yeh (1995) examined the stomach contents of two northern right whale dolphins. They determined that fish are a major component of their diet, comprising 89% of their stomach contents. ( Lanternfish were the most abundantly occurring fish group, comprising 89% of their fish prey. The most common fish species found were brokenline laternfishes and Warming's lanternfishes. Squid are a smaller component of their diet, comprising 11% of their stomach contents. The most common squid species found were Boreopacific armhook squid and Abraliopsis felis. Chou, et al., 1995)

Walker and Coe (1989) documented foreign body ingestion in two specimens from Santa Monica and Los Angeles, California. They discovered fronds of marine plants, a honey bee, white bird feathers, a partial plastic bag, several small pieces of blue vinyl plastic and a rusted metal bottle cap inside individual. ( Jefferson and Newcomer, 1993; Jefferson and Newcomer, 1993; Walker and Coe, 1989)

Predation

Natural predators of northern right whale dolphins are unknown, but likely include ( orcas and large sharks. Jefferson and Newcomer, 1993; Jefferson, et al., 1994a)

Ecosystem Roles

Northern right whale dolphins host several species of internal parasites; ( Nasitrema species in their brain and air sinuses, Crassicauda species in their inner ear complex and air sinuses, Anisakis simplex in their stomach, Monorygma grimaldii in their peritoneal cavity, Phyllobothrium delphini in their blubber, and Sarcosporidia in their skeletal muscles. External parasites of northern right whale dolphins include barnacles, such as Xenobalanus species, and copepods including Penella and Nasitrema species, which are thought to cause major damage to their brain and air sinuses and may play a role in their strandings and death. The effects of most parasites are largely unknown, but heart scars, lung abscesses and inflammation, pulmonary oedema, gastric ulceration, mucosal ulceration and brain lesions were reported in some of the stranded specimens. Cowan, et al., 1986; Dailey and Walker, 1978; Jefferson and Newcomer, 1993; Jefferson, et al., 1994a)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Northern right whale dolphins are occasionally captured by Japanese small ( cetacean whalers for food, oil, leather and fertilizers. Their flesh, heart, liver and kidneys are consumed, their blubber provides oil, their hide is tanned into low grade leather and their skeleton and other viscera are used as fertilizer. Robards and Reeves, 2011; Wilke, et al., 1953)

food

body parts are source of valuable material

Economic Importance for Humans: Negative

Northern right whale dolphins feed on commercially important squid species. They are known to occur in areas frequently used by commercial fisherman, and could possibly be seen as competition. ( Leatherwood and Walker, 1979)

Conservation Status

Mangel (1993) has estimated a mean population size of 247,000 individuals in the North Pacific, with a 95% confidence interval of 61,000 to 1,004,000 individuals. However, it should be noted that the lower limit (61,000 individuals) is believed to be biologically unreasonable. ( Mangel, 1993)

The main threat to northern right whale dolphins was the large scale pelagic driftnet fishery that operated out of Japan, Korea and Taiwan. Dolphins would become entangled in driftnets set for squid, and drown. Entangled individuals were occasionally freed, but future survival was unlikely due to the injuries commonly sustained during entanglement. These injuries could include fishing gear still attached to the animal that could impair their movements or ability to eat, ingestion of hooks, open bodily wounds, and damage or loss of fins. The entanglements in driftnets were typically greatly clustered, possibly resulting in entire pods, families or other reproductive units being killed at once. Between 1985 to 1990, this fishery was estimated to kill 15,000 to 20,000 individuals each year. It was estimated that the 1978 pre-exploited population has been reduced by 24 to 73% by this fishery. In 1993, the United Nations suspended the use of large-scale pelagic drift nets, halting the slaughter of this species and many others. ( Bjorge, et al., 1992; Carretta, et al., 2003; Ferrero and Walker, 1993; Jefferson and Newcomer, 1993; Jefferson, et al., 1994b; Mangel, 1993)

Northern right whale dolphins are one of the most commonly entangled marine mammals species in the California drift gillnet fishery, targeting ( broadbill swordfishes and common thresher sharks. From 1996 to 2002, the observed mortality for this species was 31 individuals; however, the estimated mortality was 151 individuals. Due to the fact the data used to calculate this mortality estimate did not include any deaths or injuries not directly observed by researchers, it represents only a minimum estimate of mortality. Despite fishermen being required to report any interactions with marine mammals, it is highly probable the vast majority of interactions went undocumented. Carretta, et al., 2003)

Northern right whale dolphins have never been subject to extensive direct hunting, however, Japanese small ( cetacean whalers infrequently take them. They are typically killed with buckshot fired from shotguns and/or harpoons. A single company slaughtered 465 off the coast of Japan in May and June of 1949. Jefferson and Newcomer, 1993; Wilke, et al., 1953)

Contributors

Michelle Pasnak (author), University of Manitoba, Jane Waterman (editor), University of Manitoba, Leila Siciliano Martina (editor), Animal Diversity Web Staff.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

References

Au, D., D. Weihs. 1980. At high speed dolphins save energy by leaping. Macmillan Journals Ltd., 284: 548-550.

Baird, R., P. Stacey. 1993. Sightings, strandings and incidental catches of Short-finned Pilot Whales, Globicephala macrohynchus, off the British Columbia coast. International Whaling Commission, 14: 475-479.

Baird, R., P. Stacey. 1991. Status of the Northern Right Whale Dolphin, Lissodelphis borealis, in Canada. Canadian Field-Naturalist, 105: 243-250.

Bjorge, A., R. Brownell, G. Donovan, W. Perrin. 1992. Significant direct and incidental catches of small cetaceans. International Whaling Commission, 42: 178-234.

Carretta, J., T. Price, D. Peterson, R. Read. 2003. Estimates of marine mammal, sea turtle, and seabird mortality in the California drift gillnet fishery for Swordfish and thresher shark, 1996-2002. Marine Fisheries Review, 66: 21-30.

Chou, L., A. Bright, S. Yeh. 1995. Stomach contents of dolphins ( Delphinus delphis and Lissodelphis borealis) from north Pacific Ocean. Zoological Studies, 34: 206-210.

Cowan, D., W. Walker, R. Brownell. 1986. Pathology of Small Cetaceans Stranded Along Southern California Beaches. Pp. 323-367 in M Bryden, R Harrison, eds. Research on Dolphins. Oxford: Oxford University Press.

Dailey, M., W. Walker. 1978. Parasitism as a factor in single strandings of southern California cetaceans. International Journal for Parasitology, 64: 593-596.

Ferrero, R., R. Hobbs, G. Van Blaricom. 2002. Indications of habitat use patterns among small cetaceans in the central north Pacific based on fisheries observer data. Journal of Cetacean Research and Management, 4: 311-321.

Ferrero, R., W. Walker. 1993. Growth and reproduction of the Northern Right Whale Dolphin, Lissodelphis borealis, in the offshore waters of the North Pacific Ocean. Canadian Journal of Zoology, 71: 2335-2344.

Fitch, J., R. Brownell. 1968. Fish otoliths importance in cetacean stomachs and their interpreting feeding habits. Journal of the Fisheries Research Board of Canada, 25: 2561-2574.

Forney, K., J. Barlow. 1998. Seasonal patterns in the abundance and distribution of California cetaceans. Marine Mammal Science, 14: 460-489.

Hammond, P., G. Bearzi, A. Bjorge, K. Forney, L. Karkzmarski, T. Kasuya, W. Perrin, M. Scott, J. Wang, R. Wells, B. Wilson. 2013. "Lissodelphis borealis" (On-line). IUCN Red List of Threatened Species, Version 2013. Accessed October 29, 2013 at http://www.iucnredlist.org/.

Jefferson, T., S. Leatherwood, M. Webber. 1994. FAO Species Identification Guide Marine Mammals of the World. Rome: United Nations Environment Programme and Food and Agriculture Organization of the United Nations.

Jefferson, T., M. Newcomer. 1993. Mammalian species, Lissodelphis borealis. The American Society of Mammalogists, 425: 1-6.

Jefferson, T., M. Newcomer, S. Leatherwood, K. Van Waerebeek. 1994. Right Whale Dolphins - Lissodelphis borealis (Peale, 1848) and Lissodelphis peronii (Lacepede, 1804). Pp. 335-362 in S Ridgway, S Harrison, eds. Handbook of Marine Mammals, Volume 5: The First Book of Dolphins. London: Academic.

Kajimura, H., T. Loughlin. 1988. Marine mammals in the oceanic food web of the eastern subarctic Pacific. Bulletin of the Ocean Research Institute, University of Tokyo, 26: 187-223.

Kasuya, T. 1971. Consideration of distribution and migration of toothed whales off the Pacific coast of Japan based upon aerial sighting record. Scientific Reports of the Whales Research Institute, 23: 37-60.

Leatherwood, J. 1974. A note on Gray Whale behavioral interactions with other marine mammals. Marine Fisheries Review, 36: 50-51.

Leatherwood, S., W. Walker. 1979. Right Whale Dolphins - Lissodelphis borealis Peale in the Eastern North Pacific. Pp. 282-293 in H Winn, B Olla, eds. Behavior of Marine Animals, Volume 3: Cetaceans. New York: Plenum Press.

Mangel, M. 1993. Effects of high-seas driftnet fisheries on the Northern Right Whale Dolphin Lissodelphis borealis. Ecological Applications, 2: 221-229.

Nishiwaki, M. 1967. Distribution and migration of marine mammals in the north Pacific area. Bulletin of the Ocean Research Institute, University of Tokyo, 1: 1-64.

Okada, Y., T. Hanaoka. 1940. A study of Japanese Delphinidae (IV): Tursio borealis (Peale) "Semi-iruka". Scientific Reports of the Tokyo Bunrika Daigaku, 4: 285-306.

Rankin, S., J. Oswald, J. Barlow, M. Lammers. 2007. Patterns burst-pulse vocalizations of the Northern Right Whale Dolphin, Lissodelphis borealis. Journal of the Acoustical Society of America, 121: 1213-1218.

Robards, M., R. Reeves. 2011. The global extent and character of marine mammals consumptions by humans: 1970-2009. Biological Conservation, 144: 2770-2786.

Walker, W. 1975. Review of the live-capture fishery for smaller cetaceans taken in southern California waters for public display, 1966-73. Journal of the Fisheries Research Board of Canada, 32: 1197-1211.

Walker, W., J. Coe. 1989. Survey of marine debris ingested by odontocete cetaceans. Proceedings of the Second International Conference on Maine Debris, 2: 747-774.

Wilke, F., T. Taniwaki, N. Kuroda. 1953. Phocoenides and Lagenorhynchus in Japan, with notes of hunting. Journal of Mammalogy, 34: 488-497.

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Lissodelphis borealis (northern right whale dolphin)

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Northern right whale dolphins (Lissodelphis borealis) are endemic to the waters of the North Pacific Ocean. On the eastern coast of Asia, they are found from Paramushir Island, Russia to Cape Nojima, Japan. On the western coast of North America, they have been documented from Vancouver Island, Canada to Baja California, Mexico.

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Update: This animal has been renamed! It used to be Leviathan until someone pointed out to the authors that the name had already been taken!

In today's oceans, killer whales hunt other species of whales, working in packs to take down their much bigger prey. But living whales have it easy. Those that swam off the coast of Peru around 12 million years ago were hunted by a far bigger predator, a recently discovered animal with a very appropriate name: Livyatan.

Livyatan melvillei, named after the Biblical sea monster and the author of Moby Dick author of Moby Dick, was a giant sperm whale that has just been discovered by Belgian scientist Olivier Lambert. At between 13.5 and 18.5 metres in length, it was no bigger than the modern sperm whale, but it was clearly far more formidable.

Today's sperm whale has no functional teeth in its upper jaw and only small ones in its lower jaw (which are mostly used in fights). It feeds through suction, relying on a rush of water to carry its prey into its open mouth. But Livyatan's mouth was full of huge teeth, the largest of which were a foot long and around 4 inches wide. This was no suction feeder! Livyatan clearly grabbed its prey with a powerful bite, inflicting deep wounds and tearing off flesh as killer whales do, but with a skull three times bigger.

Livyatan was at the very top of the food chain and it must have needed a lot of food. While modern sperm whales mainly eat squid, Lambert thinks that Livyatan used its fearsome teeth to kill its own kind - the giant baleen whales. At the same point in prehistory, baleen whales started becoming much bigger and they were certainly the most common large animals in the area that Leviathan lived in. Lambert thinks that the giant predator evolved to take advantage of this rich source of energy. He says, "We think that medium-size baleen whales, rich in fat, would have been very convenient prey for Livyatan ."

It's perhaps no coincidence that the biggest shark in history - the mighty Megalodon - also appeared at the same time in the same part of the world. It too was thought to have hunted whales and many of its teeth have also been found at Cerro Colorado. For the moment, it's hard to say if the two predators were direct competitors, since they may have swum in different parts of the Peruvian seas. Lambert speculates that the adults of either species could have eaten the young of the other but there's no evidence for this yet.

In the last few years, other smaller prehistoric sperm whales have been found in Peru and Italy. Their powerful teeth told us that these predators bit their prey in the manner of killer whales. The teeth were generally quite small but, as early as 1877, fossil hunters have found much larger teeth that looked very much like those of a sperm whale. The teeth provided tantalising hints of a much bigger animal but they were never accompanied by an actual skull. Their owner remained an enigma.

Lambert set out to find that skull in 2006, leading several expeditions into Peru's Pisco-Ica desert. The digs weren't fruitful but the team's luck took a turn for the amazing at the very end. "In November 2008, on the last day of the field trip, my Dutch colleague Klaas Post discovered a very large cetacean skull," says Lambert. "Usually large skulls belong to baleen whales, but Klaas immediately noted enormous teeth, both on the upper and lower jaw." They had found Livyatan.

The skull is beautifully adapted to capture large, powerful prey. The snout was short and wide, allowing it to bite more strongly with its front teeth and resist the struggles of its prey. Its temporal fossa - the shallow depression on the side of the skull - was enormous and could old huge jaw-closing muscles. The bite would have been the largest of any tetrapod (the animal group that includes mammals, birds, reptiles and amphibians). And the teeth were deeply embedded in the jaw bones for each support, and interlocked to give the animal a shearing, meat-carving bite. They were also angled forwards, giving Livyatan a better grip on prey with curved bodies.

The skull also creates a mystery. Sperm whales have a unique organ in their heads called the spermaceti, and Livyatan's was particularly large. The spermaceti is full of a waxy substance that was originally thought to be the animal's sperm (hence the name). Its purpose isn't clear although there are many theories, all of which must now be considered in the light of Livyatan 's very different lifestyle.

The sperm whale might use it to control its buoyancy during a dive by pumping in cold water, solidifying the wax and increasing the density of its head. At the depths, the energy expended during a hunt heats up the wax and melts it again. But Livyatan probably didn't hunt for squid and probably wasn't a deep-diver like the modern sperm whale. In light of this, other explanations become more intriguing. The case containing the spermaceti could be used as a battering ram during fights. It could also boost the sperm whale's echolocation, allowing it to stun its prey with sound, or woo females (the male's organ is particularly big).

Nature http://dx.doi.org/10.1038/nature09067

More on ancient whales:

If the citation link isn't working, read why here

Livyatan

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Behold Livyatan: the sperm whale that killed other whales

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Update: This animal has been renamed! It used to be Leviathan until someone pointed out to the authors that the name had already been taken! In today's oceans, killer whales hunt other species of whales, working in packs to take down their much bigger prey. But living whales have it easy.

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https://www.fisheries.noaa.gov/species/gervais-beaked-whale

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Species Directory

What We Do

Conservation & Management

All Gervais' beaked whales are protected under the MMPA. Our work protects this species by:

Reducing interactions with commercial and recreational fishing gear

Implementing requirements to reduce serious injuries and mortalities

Minimizing the effects of vessel disturbance, noise, and other types of human impacts

Learn more about our conservation efforts

Science

Our research projects have helped us better understand Gervais' beaked whales and the challenges they face. Our work includes:

Stock assessments

Acoustic monitoring

Learn more about our research

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This mapping tool shows when and where specific whale, dolphin, and other...

Data & Maps

This mapping tool shows when and where specific whale, dolphin, and other cetacean species were...

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Gervais' beaked whales are little known members of the beaked whale family, Ziphiidae. Sometimes called the "Antillean" or "Gulf Stream beaked whale," this species prefers deep tropical, subtropical, and warm temperate waters of the Atlantic Ocean but is occasionally found in colder temperate seas.

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Brett Clark teaches sociology at North Carolina State University in Raleigh. Rebecca Clausen teaches sociology at Fort Lewis College in Durango, Colorado.

The world ocean covers approximately 70 percent of the earth. It has been an integral part of human history, providing food and ecological services. Yet conservation efforts and concerns with environmental degradation have mostly focused on terrestrial issues. Marine scientists and oceanographers have recently made remarkable discoveries in regard to the intricacies of marine food webs and the richness of oceanic biodiversity. However, the excitement over these discoveries is dampened due to an awareness of the rapidly accelerating threat to the biological integrity of marine ecosystems.1

At the start of the twenty-first century marine scientists focused on the rapid depletion of marine fish, revealing that 75 percent of major fisheries are fully exploited, overexploited, or depleted. It is estimated "that the global ocean has lost more than 90% of large predatory fishes." The depletion of ocean fish stock due to overfishing has disrupted metabolic relations within the oceanic ecosystem at multiple trophic and spatial scales.2

Despite warnings of impending collapse of fish stock, the oceanic crisis has only worsened. The severity is made evident in a recent effort to map the scale of human impact on the world ocean. A team of scientists analyzed seventeen types of anthropogenic drivers of ecological change (e.g., organic pollution from agricultural runoff, overfishing, carbon dioxide emissions, etc.) for marine ecosystems. The findings are clear: No area of the world ocean "is unaffected by human influence," and over 40 percent of marine ecosystems are heavily affected by multiple factors. Polar seas are on the verge of significant change. Coral reefs and continental shelves have suffered severe deterioration.

Additionally, the world ocean is a crucial factor in the carbon cycle, absorbing approximately a third to a half of the carbon dioxide released into the atmosphere. The increase in the portion of carbon dioxide has led to an increase in ocean temperature and a slow drop in the pH of surface waters-making them more acidic-disrupting shell-forming plankton and reef-building species. Furthermore, invasive species have negatively affected 84 percent of the world's coastal waters-decreasing biodiversity and further undermining already stressed fisheries.3

Scientific analysis of oceanic systems presents a sobering picture of the coevolution of human society and the marine environment during the capitalist industrial era. The particular environmental problems related to the ocean cannot be viewed as isolated issues or aberrations of human ingenuity, only to be corrected through further technological development. Rather these ecological conditions must be understood as they relate to the systematic expansion of capital and the exploitation of nature for profit. Capital has a particular social metabolic order-the material interchange between society and nature-that subsumes the world to the logic of accumulation. It is a system of self-expanding value, which must reproduce itself on an ever-larger scale.4 Here we examine the social metabolic order of capital and its relationship with the oceans to (a) examine the anthropogenic causes of fish stock depletion, (b) detail the ecological consequences of ongoing capitalist production in relation to the ocean environment, and (c) highlight the ecological contradictions of capitalist aquaculture.5

Marine Metabolism: Biological Richness, Energy Cycles, and Trophic Levels

Ecologists now appreciate the complexity of biological relationships at multiple scales, including primary productivity, carbon sequestration, and intricate food webs. New light is being shed on oceanic ecosystems offering an emerging picture of the sea's metabolism. In particular, research reveals great complexity and a resultant integrity among trophic level interactions (food webs) between microscopic organisms, plankton, and larger predators. Ivan Valiela, a marine biologist, states:

No topic within marine ecology and biological oceanography has changed more...than our notions about components and structure of planktonic food webs. Knowledge about marine water column food webs has been considerably enlarged, and made much more complex, by recent findings about the existence and role of smaller organisms, release and reuse of dissolved organic matter, and reassessment of the function of certain larger organisms.6

The metabolic interactions expressed among trophic levels are proving to be the underlying source of great biological wealth and ocean resiliency.

According to marine scientists, "the genetic, species, habitat, and ecosystem diversity of the oceans is believed to exceed that of any other Earth system." For example, ocean environments contain seventeen different taxa of life forms compared to eleven land-based taxa. Oceans account for 99 percent of the volume that is known to sustain life-most of which is still unknown. Scientists exploring the ocean's middle depths have discovered a host of new species composing productive ecosystems. The deep-sea bottom, of which little more than 1.5 percent has been explored, has recently been the object of great interest due to its abundant biodiversity.

For example, in one such Atlantic seafloor with an area of approximately twenty-one square meters, scientists sampled and found 90,672 individual organisms representing 798 species, of which 460 were previously unknown. These new discoveries have yielded important insights regarding marine ecosystems. At the same time, they produce an appreciation of the great uncertainty that still exists for much of the marine environment's processes, such as the role of currents, nutrient cycles, and biomass.7

Recent advances in trophic level understanding have developed in three areas: microbial interactions, multi-tiered trophic dynamics, and upper trophic level controls. First, the new array of facts offered by studying the base of the food web (diatoms, dinoflagellates, and other microalgae) has led marine researchers to propose a new view of the planktonic food web that includes a "microbial loop." In the microbial loop, organic matter cycles through microbes before entering the classic food web; this is a more complicated relationship than was previously assumed.

Second, it has been found that oceanic food webs often have five trophic levels or more, as opposed to freshwater systems where three levels are more typical. Valiela describes this yet-unexplained discovery as a significant qualitative difference between the two environments. Previously, trophic interactions among freshwater fish were thought to be analogous to pelagic fish and management decisions were based on such comparisons. Exploring the multi-tiered dynamics of ocean food webs as unique from freshwater systems provides a more complex research question for the scientific community. Uncertainty colors all speculation of how vulnerable ocean systems are compared to freshwater and land ecologies.8

Finally, researchers have found that species in the upper trophic positions seem to be closely coupled to food availability. This means that the top predators exist near the carrying capacity of their environment. This is not the case with most bony fishes in freshwater environments, which usually exist in an environment with an abundant prey population. The life history characteristics of the upper trophic creatures suggest they are easily susceptible to overexploitation. Little room exists in the population of top marine predators to absorb losses of food resources.

For example, the ability of whales to recover to their earlier abundance after massive human predation is now dependent on the availability of krill. Although the large-scale hunting of whales has dramatically declined, the massive exploitation of krill as a protein source and as an animal-feed additive may now jeopardize recovering whale populations dependent on krill as a food supply.9

There is a significant amount of interaction and dependence of the ocean's top predators on lower trophic levels. Trophic level interactions represent a marine food web based on energy flow and describe one element of the ocean's metabolism. Many other relationships besides trophic level interactions exist between ocean organisms, such as the relation between organisms and their immediate habitat, which can include coral reefs and kelp forests. Both of these realms, on which species depend, are highly vulnerable to resource exploitation.

Capitalism and Marine Fishery Exploitation

Humans have long been connected to the ocean's metabolic processes by harvesting marine fish and vegetation. Harvesting methods and processes have varied depending on the structure of social production. Subsistence fishing is a practice woven throughout human history, beginning with the harvesting of shellfish along seashores and shallow lakes, and progressing with the development of tools such as stone-tipped fishing spears, fishhooks, lines, and nets. This was originally based upon fishing for use of the fish. What was caught was used to feed families and communities. Through the process of fishing, human labor has been intimately linked to ocean processes, gaining an understanding of fish migrations, tides, and ocean currents.

The size of a human population in a particular region influenced the extent of exploitation. But the introduction of commodity markets and private ownership under the capitalist system of production altered the relationship of fishing labor to the resources of the seas. Specific species had an exchange value. As a result, certain fish were seen as being more valuable. This led to fishing practices that focused on catching as many of a particular fish, such as cod, as possible. Non-commercially viable species harvested indiscriminately alongside the target species were discarded as waste.

As capitalism developed and spread, intensive extraction by industrial capture fisheries became the norm. Increased demands were placed on the oceans and overfishing resulted in the severe depletion of wild fish stocks. In Empty Ocean, Richard Ellis states, "Throughout the world's oceans, food fishes once believed to be immeasurable in number are now recognized as greatly depleted and in some cases almost extinct. A million vessels now fish the world's oceans, twice as many as there were twenty-five years ago. Are there twice as many fish as before? Hardly." How did this situation develop?10

The beginning of capitalist industrialization marked the most noticeable and significant changes in fisheries practices. Mechanization, automation, and mass production/consumption characterized an era of increased fixed capital investments. Profit-driven investment in efficient production led to fishing technologies that for the first time made the exhaustion of deep-sea fish stocks a real possibility. Such transformations can be seen in how groundfishing, the capture of fish that swim in close proximity to the ocean's bottom, changed through the years.

Industrialization began to influence the groundfishery around the early 1900s, as technological developments were employed to further the accumulation of capital. The introduction of steam-powered trawlers from England in 1906 heralded a significant change in how groundfish were caught and rapidly replaced the sail-powered schooner fleets. Prior to steam trawling, groundfish were caught on schooners with baited lines during long journeys at sea. Due to lack of refrigeration and freezing, most of the cod catch was salted.

The competitive markets organized under capitalist production welcomed the increased efficiency of steam-powered vessels, without a critical assessment of the consequences of increased harvest levels. More captured fish meant more profit. The switch to trawling was complete by 1920, and the consequences of the second industrial revolution organized under capitalist forces would soon change the human-nature relationship to the ocean, extending the reach of capital.

The expanded geographic range and speed of fishing fleets allowed for increased productivity of catch as well as increased diversity of captured species that were deemed "valuable" on the market. Technological developments and improved transportation routes allowed the fishing industry to grow, increasing its scale of operations. Cold storage ensured that fish would be fresh, reducing spoilage and loss of capital. In Cod: A Biography of the Fish that Changed the World, Mark Kurlansky explains, "Freezing [cod] also changed the relationship of seafood companies to fishing ports. Frozen fish could be bought anywhere-wherever the fish was cheapest and most plentiful. With expanding markets, local fleets could not keep up with the needs of the companies." Advances in the transportation infrastructure allowed people in the Midwest to consume the increased harvests of cod and haddock, leading to a significant expansion in the market. Major marketing campaigns promoted the consumption of fish to increase sales. Together these factors enhanced the accumulation of capital within the fishing industry, and companies invested some of this capital back into their fleets.11

By 1930 there were clear signals that the groundfishing fleet's ability to capture massive quantities of fish had surpassed natural limits in fisheries. A Harvard University investigation reported that in 1930 the groundfishery landed 37 million haddock at Boston, with another 70-90 million juvenile haddock discarded dead at sea. The sudden rise in fisheries harvest (creating a subsequent rise in consumer demand through marketing campaigns) resulted in stress in the groundfish populations, and landings plummeted.

Competitive markets create incentives to expand production, regardless of resource decline. Thus, in reaction to decreased stocks due to overfishing, groundfishing fleets moved farther offshore into waters off of the coast of Canada to increase the supply of valuable fish to new markets. The fleet's ability to continue moving into unexploited waters obscured recognition of the severe resource depletion that was occurring. As a result, the process of overfishing particular ecosystems to supply a specific good for the market expanded, subjecting more of the ocean to the same system of degradation.12

The distant water fleets were made possible by the advent of factory trawlers. Factory trawlers represent the pinnacle of capital investment and extractive intensification in the global fisheries. In Distant Water William Warner presents a portrayal of a factory trawler's capacity:

Try to imagine a mobile and completely self-contained timber cutting machine that could smash through the roughest trails of the forest, cut down trees, mill them, and deliver consumer-ready lumber in half the time of normal logging and milling operations. This was exactly what factory trawlers did-this was exactly their effect on fish-in the forests of the deep. It could not long go unnoticed.

Factory trawlers pull nylon nets a thousand feet long through the ocean, potentially capturing 400 tons of fish during a single netting. Industrial trawlers can process and freeze their catch as they travel.13 Such technological development extended the systematic exploitation and scale of harvesting of fishes.

The natural limits of fish populations combined with capital's need to expand led to the development of immense trawlers that increased the productive capacity and efficiency of operations. These ships allowed fishermen to seek out areas in the ocean where valuable fish were available, providing the means to capture massive quantities of fish in a single trip. Overcoming the shortage of fishes in one area was accomplished by even more intensive harvesting with new ships and equipment, such as sonar, in other regions of the oceans. The pursuit of vast quantities of commercial fishes in different areas of the ocean expanded the depletion of other species, as they were exploited and discarded as bycatch. The swath of the seas subjected to the dictates of the market increased, whether a fish was sold as a commodity or thrown overboard as a waste product.14

Competition for market share between companies and capital's investment in advanced technology intensified fishery exploitation. Competing international companies sought nature's diminishing bounty, causing further international conflict in the "race for fish." President Truman responded to these disputes by attempting to expand U.S. corporate interests. He issued two proclamations expanding U.S. authority beyond territorial waters trying to further territorial enclosure of its adjacent seas out to the limits of the continental shelf. Coastal states around the world struggled to transform the property rights of the open ocean to benefit their nations. In response to growing conflict, the United Nations convened the First United Nations Conference on the Law of the Sea in Geneva in 1958.

Eventually, most nations voted to sign the UN Law of the Sea article, "irrevocably transforming" international law and constituting "a fundamental revision of sometimes age-old institutions."15 (The U.S. Senate, however, has still not ratified the Law of the Sea Convention.) In the end, the convention established a property regime according to the prescription of an exclusive economic zone (EEZ). The EEZ put regions of the high seas adjacent to coastal waters entirely within the management purview of the coastal state, up to two hundred miles from their shore. In this zone, states have exclusive rights to living and non-living resources for extraction and economic pursuits.

The collapse of fisheries due to overexploitation coupled with the expanding seafood market forced companies to look elsewhere for "the most traded animal commodity on the planet." African nations-such as Senegal, Mauritania, Angola, and Mozambique-confronting dire economic conditions sold fishing access to European and Asian nations and companies. In the case of Mauritania, selling fishing access provided over $140 million a year, which equaled a fifth of the government's budget. Few countries can resist such bait, given the need for monetary resources. Industrialized trawlers descended into African waters, combing their seas for the treasured fish commodities. In the past three decades, Africa's fish population in the ocean has decreased by 50 percent and thousands of fishermen have become unemployed.16 The expansion of capitalist fishing practices continues to decimate fisheries and spread ecological degradation, as profits and food are funneled back to core nations.

The Food and Agriculture Organization estimates that the world capture from fisheries increased from approximately 20 million tons in 1950 to 84.2 million tons in 2005. A dominant narrative explains that human population growth is solely responsible for this increase in capture; however, recent research demonstrates that social structural factors such as economic growth are also propelling the depletion. Since around 1989 the world capture of marine fish has declined by 500,000 tons per year amidst increasing fishing effort.

There have been sharp declines in the populations of tuna, cod, and marlins. During the 1960s and '70s, shelf fisheries in the Atlantic started to collapse as a result of overfishing. Operations moved to the deep sea. Deepwater fishing has seriously affected the populations of deep-sea fish, such as the roundnose grenadier, onion-eye grenadier, spiny eel, spinytail skate, and blue hake. The populations of these deep-sea fishes have plummeted by over 87 percent in seventeen years. It is expected that these fishes will be driven to the point of extinction-to the detriment of the ecosystems in which they live. Part of the vulnerability of these fishes is that they can live to around sixty years of age and do not sexually mature until their late teen years.17

Changes in the market can transform the demand for particular fish species. In the early 1900s, bluefin tuna was seen as being only suitable for use as pet food. But given their strength and size-weighing up "to three quarters of a ton and [having] a length of four meters"-they were deemed worthy opponents to be hunted. In the later half of the twentieth century, bluefin tuna became "the most desirable food fish in the world" with the spread of sushi and sashimi restaurants. Given the machinations of capitalism, this has also caused them to become "the most endangered of all large fish species."

The bluefin tuna population continues to be decimated by overfishing, and the practice of capturing half-grown tuna at sea and placing them in floating pens-known as tuna ranches-where they are fed until they are ready for market has only worsened the situation. While this helps control the production process, it involves catching the fishes "before they are old enough to breed" and keeping "them penned up until they are killed." As a result of this practice and overfishing, bluefin tuna are threatened with depletion.18

The geographic span of ocean exploitation has widened as capitalist operations of extraction continue. Even the Antarctic waters are increasingly under assault as the fishing industry gears up to plunder the krill population. Since the 1970s the numbers of krill have declined by 80 percent, largely due to global warming. But fishing operations are adding to the depletion. These tiny crustaceans eat carbon-rich food near the surface of the water, thereby they help remove the greenhouse gas carbon dioxide.

They have long been one of the primary sources of food for seals, whales, and penguins. Progressively they have been incorporated into the insatiable appetite of global capital. "Suction harvesting" swallows up huge quantities that are processed, frozen, and stored on newly outfitted ships. From here, the krill are to be used as feed for fish-farms (aquaculture) or transformed into omega-3 oil and other health supplements.19

Fleets of ships burning fossil fuels to harvest from the open oceans have exacerbated the deterioration of marine ecosystems. The depletion of fish stock increases the distance that is necessary to travel in order to catch certain species of fish, such as tuna and swordfish. It also expands the regional scope of exploitation, the number of species captured as bycatch, and the scale of depletion. In 2000, 80 million tons of fish required the burning of 13 billion gallons of fuel and the release of approximately 134 million tons of carbon dioxide. This means that global fisheries used up to 12.5 times the amount of fuel energy that they provided as edible-protein energy.20

During the 1970s and '80s fishing ships became more automated, with the trend toward full automation becoming common. Today, navigational aids, such as geographic positioning systems (GPS), and weather prediction models enhance the ability of fishing fleets to catch the most amount of fishes in the shortest amount of time, with the least amount of human labor. The synthesis of technical development and transformed property rights under the competitive framework of global capitalism has resulted in the massive extraction of marine fish and an intensified social metabolism organized for the pursuit of profit.

Ecological Degradation of Marine Ecoystems

Species-Level Effects

The intensified extraction of fish from already stressed oceanic ecosystems-fueled by capital accumulation and the free appropriation of nature-has resulted in significant consequences to the metabolic interactions between marine trophic levels. Marine scientists note that the removal of 100 million metric tons (which includes both capture and aquaculture) of fish from the world ocean will lead to long-term, large-scale disruptions in marine ecology. Of direct concern are "species level effects," in particular the removal of target and non-target marine life. Continued harvest of fish species to population levels that are below the sustainable numbers required for reproduction will eventually lead to extinction.

The orange roughy, for example, began to be commercially exploited ten years ago. This fish lives to be 150 years old and only begins to reproduce at age 25. By continually removing the oldest fish first, the industry has depleted the population of reproducing adults. (Harvesting this fish generally results in the destruction of coral forests.) The orange roughy species is now threatened with extinction. As mentioned earlier, the depletion of fish stock for commercial fishing in coastal waters led to the capture of fishes in the deep sea-such as roundnose grenadier, onion-eye grenadier, spiny eel, spinytail skate, and blue hake-subjecting them to the dictates of the market, driving them to the point of extinction.21

Industrialized capitalist fishing allows for vast quantities of target fish to be harvested at once. At the same time, it leads to an immense amount of non-target marine life-bycatch-being captured. Bycatch are commercially unviable species, thus they are seen as waste. The "trash fish" are often ground up and thrown back into the ocean. Part of the bycatch includes juveniles of the target fish, which, if the mortality is increased among this population, undercuts the success of recovery. Obviously, the populations of the discarded species are negatively affected by this practice, furthering the depletion of marine life. The most wasteful operation is trawling for shrimp. The capture and discarding of bycatch disrupts the habitats and trophic webs within ecosystems. The scale of the disruption is quite significant. It is estimated that an average of 27 million tons of fish are discarded each year in commercial fisheries around the world, and that the United States has a .28 ratio of bycatch discard to landings.22

Species extinction is the direct impact of overfishing, which is in part driven by the pursuit of capital accumulation and is facilitated by the technological innovations that are employed for this particular purpose, in what has become known as a "race for fish."23 Capitalist practices are creating a loss of marine biodiversity and undermining the resiliency of marine ecosystems. Valiela states, "The magnitude of the fishing harvest and the examples of major alterations to marine food webs by predator removal suggest that effects of fishing are ecologically substantial at large spatial scales." The "major alteration to marine food webs" due to overexploitation provides the clearest example of ecological degradation in the metabolic processes of the ocean.24

Fishing Down the Food Chain

Equally disrupting, but less apparent than species effects, are the ecosystem effects caused by fishery exploitation, especially "fishing down the food chain."25 As overfishing depletes the most commercially viable top predators (i.e., snapper, tuna, cod, and swordfish), competition drives commercial fishers to begin harvesting species of lower trophic levels. The downward shift is global, according to the model analysis of UN statistics describing worldwide catches of fish over a forty-year time span. If this quest is pursued to its logical end, scientists warn it will lead to the wholesale collapse of marine ecosystems. Fishing down the food chain erodes the base of marine biodiversity and undermines the biophysical cornerstone of ocean fisheries. The recent discoveries of marine trophic interactions suggest that the lower trophic levels of marine food webs provide an integral and complex foundation-disrupting this base undermines the metabolic cycle of energy flows within marine ecosystems.

Overfishing of lower trophic levels has shortened the food chain and sometimes has removed one or more of the "links," increasing the system's vulnerability to natural and human induced stresses. For example, in the North Sea the cod population has been so depleted that fishermen are now harvesting a lower trophic species called pout, which the cod used to eat. The pout eat krill and copepods. Krill also eat copepods. As the pout are commercially harvested, the krill population expands and the copepod population declines drastically. (In other areas of the ocean, krill are captured and used as an animal-feed additive, hindering the recovery of the whales that depend upon them for food.) Because copepods are the main food of young cod, the cod population cannot recover from initial fisheries exploitation.26

Fishing down the food chain illustrates how capture fisheries organized under competitive market conditions and the drive to accumulate capital are dismantling the marine ecological system that has been developing for millions of years. In addition, fishing for lower trophic level species deceptively masks marine fish extraction, as millions of tons of fish are harvested each year from the oceans. People continue to be provided with seafood on their menus, never realizing the full impact of overfishing the top predators. Fishing down the food chain, due to overfishing in the higher tropic levels, depletes the food resources on which predatory fishes depend. As noted earlier, marine predatory species are extremely vulnerable to losses of prey.

Collapse of Coastal Marine Ecosystems

The previous examples demonstrate how species extinction decreases the resiliency of trophic level interactions. Even more problematic, however, is the widespread collapse of entire ecosystems resulting from overfishing. Historical data suggests that species and population declines due to overfishing are direct preconditions for the collapse of entire coastal ecosystems. The collapse of whole-scale ecosystems not only threatens the ecological resiliency of the marine environment, but also disrupts the human populations that rely on the coastal ecosystem for subsistence or livelihoods. "Overfishing and ecological extinction predate and precondition modern ecological investigations and the collapse of marine ecosystems in recent times, raising the possibility that many more marine ecosystems may be vulnerable to collapse in the near future."27

Kelp forests, coral reefs, seagrass beds, and estuaries are examples of coastal ecosystems that have collapsed in parts of the world due to overfishing and other forms of environmental degradation. These ecosystems provide complex habitats for a multitude of species and often are the foundation of many local fishing communities. For example, the kelp forests of the Gulf of Maine experienced severe deforestation and widespread reductions in the number of trophic levels due to the population explosion of sea urchins, the primary herbivores that eat kelp. The following account details such a sequence of events:

Atlantic cod and other large ground fish are voracious predators of sea urchins. These fishes kept sea urchin populations small enough to allow persistence of kelp forests despite intensive aboriginal and early European hook-and-line fishing for at least 5000 years. New mechanized fishing technology in the 1920s set off a rapid decline in numbers and body size of coastal cod in the Gulf of Maine....Kelp forests disappeared with the rise in sea urchins due to removal of predatory fish.28

In other words, industrial fishing operations intensified the exploitation of marine ecosystems, transforming natural conditions.
A number of human activities are leading to the collapse of coral reefs. Overfishing is one of the causes. Deforestation is another. Clearing forests leads to muddy rivers filled with sediment, which moves downstream and smothers coral reefs. But the main force driving massive destruction of coral reefs is global warming. The increase of carbon dioxide in the atmosphere contributes to a warming and increase in the acidity of ocean water. As a result, multicolored, healthy coral reefs filled with a rich abundance of biodiversity are being bleached and turned into gray-white skeletons. Without radical changes to the social metabolic order, the death of the world's coral reefs could take place within a few decades. When coral reefs die, the fauna dependent upon them also die.29 Natural conditions, everywhere, are being transformed by the social metabolic order of capitalism. A general progression of environmental degradation accompanies this system of growth, creating ecological crises in the conditions of life.

The most recent changes to coastal ecosystems caused by overfishing involve microbial population explosions. The microbial loop has been found to be more sophisticated and complex than ever expected. Population explosions of microbes are responsible for increasing eutrophication, diseases of marine species, toxic bloom, and even diseases such as cholera that affect human health.30 Chesapeake Bay is now a bacterially dominated ecosystem with a trophic structure unrecognizable from that of a century ago. This rapid and drastic change in ecosystem composition is due to the overfishing of suspension feeders that filtered microbes out of the water column. Bacterial domination of Chesapeake Bay and the deforestation of kelp beds in the Gulf of Maine serve as two examples of how depletion of top predators leads to the collapse of entire ecosystems.

The immense problems associated with the overharvest of industrial capture fisheries has led some optimistically to offer aquaculture as an ecological solution. However, capitalist aquaculture fails to reverse the process of ecological degradation. Rather, it continues to sever the social and ecological relations between humans and the ocean.

Aquaculture: The Blue Revolution?

The massive decline in fish stocks has led capitalist development to turn to a new way of increasing profits-intensified production of fishes. Capitalist aquaculture represents not only a quantitative change in the intensification and concentration of production; it also places organisms' life cycles under the complete control of private for-profit ownership.31 This new industry, it is claimed, is "the fastest-growing form of agriculture in the world." It boasts of having ownership from "egg to plate" and substantially alters the ecological and human dimensions of a fishery.32

Aquaculture (sometimes also referred to as aquabusiness) involves subjecting nature to the logic of capital. Capital attempts to overcome natural and social barriers through its constant innovations. In this, enterprises attempt to commodify, invest in, and develop new elements of nature that previously existed outside the political-economic competitive sphere: As Edward Carr wrote in the Economist, the sea "is a resource that must be preserved and harvested....To enhance its uses, the water must become ever more like the land, with owners, laws and limits. Fishermen must behave more like ranchers than hunters."33

As worldwide commercial fish stocks decline due to overharvest and other anthropogenic causes, aquaculture is witnessing a rapid expansion in the global economy. Aquaculture's contribution to global supplies of fish increased from 3.9 percent of total worldwide production by weight in 1970 to 27.3 percent in 2000. In 2004, aquaculture and capture fisheries produced 106 million tons of fish and "aquaculture accounted for 43 percent."34 According to Food and Agriculture Organization statistics, aquaculture is growing more rapidly than all other animal food producing sectors.

Hailed as the "Blue Revolution," aquaculture is frequently compared to agriculture's Green Revolution as a way to achieve food security and economic growth among the poor and in the third world. The cultivation of farmed salmon as a high-value, carnivorous species destined for market in core nations has emerged as one of the more lucrative (and controversial) endeavors in aquaculture production.35 Much like the Green Revolution, the Blue Revolution may produce temporary increases in yields, but it does not usher in a solution to food security (or environmental problems). Food security is tied to issues of distribution. Given that the Blue Revolution is driven by the pursuit of profit, the desire for monetary gain trumps the distribution of food to those in need.36

Industrial aquaculture intensifies fish production by transforming the natural life histories of wild fish stocks into a combined animal feedlot. Like monoculture agriculture, aquaculture furthers the capitalistic division of nature, only its realm of operation is the marine world. In order to maximize return on investment, aquaculture must raise thousands of fish in a confined net-pen. Fish are separated from the natural environment and the various relations of exchange found in a food web and ecosystem. The fish's reproductive life cycle is altered so that it can be propagated and raised until the optimum time for mechanical harvest.

Aquaculture interrupts the most fundamental metabolic process-the ability of an organism to obtain its required nutrient uptake. Because the most profitable farmed fish are carnivorous, such as Atlantic salmon, they depend on a diet that is high in fishmeal and fish oil. For example, raising Atlantic salmon requires four pounds of fishmeal to produce every one pound of salmon. Consequently, aquaculture production depends heavily on fishmeal imported from South America to feed the farmed carnivorous species.37

The inherent contradiction in extracting fishmeal is that industries must increase their exploitation of marine fish in order to feed the farm-raised fish-thereby increasing the pressure on wild stocks to an even larger extent. Such operations also increase the amount of bycatch. Three of the world's five largest fisheries are now exclusively harvesting pelagic fish for fishmeal, and these fisheries account for a quarter of the total global catch. Rather than diminishing the demands placed on marine ecosystems, capitalist aquaculture actually increases them, accelerating the fishing down the food chain process. The environmental degradation of populations of marine species, ecosystems, and tropic levels continues.38

Capitalist aquaculture-which is really aquabusiness-represents a parallel example of capital following the patterns of agribusiness. Similar to combined animal feedlots, farmed fish are penned up in high-density cages making them susceptible to disease. Thus, like in the production of beef, pork, and chicken, farmed fish are fed fishmeal that contains antibiotics, increasing concerns about antibiotic exposure in society. In "Silent Spring of the Sea," Don Staniford explains, "The use of antibiotics in salmon farming has been prevalent right from the beginning, and their use in aquaculture globally has grown to such an extent that resistance is now threatening human health as well as other marine species." Aquaculturists use a variety of chemicals to kill parasites, such as sea lice, and diseases that spread quickly throughout the pens. The dangers and toxicities of these pesticides in the marine environment are magnified because of the long food chain.39

Once subsumed into the capitalist process, life cycles of animals are increasingly geared to economic cycles of exchange by decreasing the amount of time required for growth. Aquabusiness conforms to these pressures, as researchers are attempting to shorten the growth time required for fish to reach market size. Recombinant bovine growth hormone (rBGH) has been added to some fish feeds to stimulate growth in fishes in aquaculture farms in Hawaii. Experiments with fish transgenics-the transfer of DNA from one species to another-are being done to increase the rate of weight gain, causing altered fish to grow from 60 percent to 600 percent larger than wild stocks.40 These growth mechanisms illustrate capitalist aquaculture's drive to transform nature to facilitate the generation of profit.

In addition, aquaculture alters waste assimilation. The introduction of net-pens leads to a break in the natural assimilation of waste in the marine environment. The pens convert coastal ecosystems, such as bays, inlets, and fjords, into aquaculture ponds, destroying nursery areas that support ocean fisheries. For instance, salmon net-pens allow fish feces and uneaten feed to flow directly into coastal waters, resulting in substantial discharges of nutrients. The excess nutrients are toxic to the marine communities that occupy the ocean floor beneath the net-pens, causing massive die offs of entire benthic populations.41 Other waste products are concentrated around net-pens as well, such as diseases and parasites introduced by the caged salmon to the surrounding marine organisms.

The Blue Revolution is not an environmental solution to declining fish stocks. In fact, it is an intensification of the social metabolic order that creates ruptures in marine ecosystems. "The coastal and marine support areas needed for resource inputs and waste assimilation [is]...50,000 times the cultivation area for intensive salmon cage farming."42 This form of aquaculture places even more demands upon ecosystems, undermining their resiliency. Although aquabusiness is efficient at turning fish into a commodity for markets given the extensive control that is executed over the productive conditions, it is even more energy inefficient than fisheries, demanding more fuel energy investment than the energy produced.43 Confronted by declines in fish stock, capital is attempting to shift production to aquaculture. However, this intense form of production for profit continues to exhaust the oceans and produce a concentration of waste that causes further problems for ecosystems, undermining their ability to regenerate at all levels.

Turning the Ocean into a Watery Grave

The world is at a crossroads in regard to the ecological crisis. Ecological degradation under global capitalism extends to the entire biosphere. Oceans that were teeming with abundance are being decimated by the continual intrusion of exploitive economic operations. At the same time that scientists are documenting the complexity and interdependency of marine species, we are witnessing an oceanic crisis as natural conditions, ecological processes, and nutrient cycles are being undermined through overfishing and transformed due to global warming.

The expansion of the accumulation system, along with technological advances in fishing, have intensified the exploitation of the world ocean; facilitated the enormous capture of fishes (both target and bycatch); extended the spatial reach of fishing operations; broadened the species deemed valuable on the market; and disrupted metabolic and reproductive processes of the ocean. The quick-fix solution of aquaculture enhances capital's control over production without resolving ecological contradictions.

It is wise to recognize, as Paul Burkett has stated, that "short of human extinction, there is no sense in which capitalism can be relied upon to permanently 'break down' under the weight of its depletion and degradation of natural wealth."44 Capital is driven by the competition for the accumulation of wealth, and short-term profits provide the immediate pulse of capitalism. It cannot operate under conditions that require reinvestment in the reproduction of nature, which may entail time scales of a hundred or more years. Such requirements stand opposed to the immediate interests of profit.

The qualitative relation between humans and nature is subsumed under the drive to accumulate capital on an ever-larger scale. Marx lamented that to capital, "Time is everything, man is nothing; he is at the most, time's carcase. Quality no longer matters. Quantity alone decides everything."45 Productive relations are concerned with production time, labor costs, and the circulation of capital-not the diminishing conditions of existence. Capital subjects natural cycles and processes (via controlled feeding and the use of growth hormones) to its economic cycle. The maintenance of natural conditions is not a concern. The bounty of nature is taken for granted and appropriated as a free gift.

As a result, the system is inherently caught in a fundamental crisis arising from the transformation and destruction of nature. István Mészáros elaborates this point, stating:

For today it is impossible to think of anything at all concerning the elementary conditions of social metabolic reproduction which is not lethally threatened by the way in which capital relates to them-the only way in which it can. This is true not only of humanity's energy requirements, or of the management of the planet's mineral resources and chemical potentials, but of every facet of the global agriculture, including the devastation caused by large scale de-forestation, and even the most irresponsible way of dealing with the element without which no human being can survive: water itself....In the absence of miraculous solutions, capital's arbitrarily self-asserting attitude to the objective determinations of causality and time in the end inevitably brings a bitter harvest, at the expense of humanity [and nature itself].46

An analysis of the oceanic crisis confirms the destructive qualities of private for-profit operations. Dire conditions are being generated as the resiliency of marine ecosystems in general is being undermined.

To make matters worse, sewage from feedlots and fertilizer runoff from farms are transported by rivers to gulfs and bays, overloading marine ecosystems with excess nutrients, which contribute to an expansion of algal production. This leads to oxygen-poor water and the formation of hypoxic zones-otherwise known as "dead zones" because crabs and fishes suffocate within these areas. It also compromises natural processes that remove nutrients from the waterways. Around 150 dead zones have been identified around the world. A dead zone is the end result of unsustainable practices of food production on land. At the same time, it contributes to the loss of marine life in the seas, furthering the ecological crisis of the world ocean.

Coupled with industrialized capitalist fisheries and aquaculture, the oceans are experiencing ecological degradation and constant pressures of extraction that are severely depleting the populations of fishes and other marine life. The severity of the situation is that if current practices and rates of fish capture continue marine ecosystems and fisheries around the world could collapse by the year 2050.47 To advert turning the seas into a watery grave, what is needed is nothing less than a worldwide revolution in our relation to nature, and thus of global society itself.

Notes
1. Ivan Valiela, Marine Ecological Processes (New York: Springer, 1995); Jeremy B. Jackson, et al., "Historical Overfishing and the Recent Collapse of Coastal Ecosystems," Science 293 (2001): 629-37.
2. Pew Oceans Commission, America's Living Oceans (Arlington, Va.: PEW, 2003), v; Food and Agriculture Organization (FAO) of the United Nations, The State of World Fisheries and Aquaculture (Rome: FAO, 2002), 23; Ransom A. Meyers and Boris Worm, "Rapid Worldwide Depletion of Predatory Fish Communities," Nature 423 (2003): 280-83; Jennie M. Harrington, Ransom A. Myers, and Andrew A. Rosenberg, "Wasted Fishery Resources," Fish & Fisheries 6, no. 4 (2005): 350-61.
3. Benjamin S. Halpern, et al., "A Global Map of Human Impact on Marine Ecosystems," Science 319 (2008): 948-952; Jennifer L Molnar, et al., "Assessing the Global Threat of Invasive Species to Marine Biodiversity," Frontiers in Ecology and the Environment 6 (2008), doi:10.1890/070064; Callum Roberts, The Unnatural History of the Sea (Washington, DC: Island Press, 2007).
4. István Mészáros, Beyond Capital (New York: Monthly Review Press, 1995), 40-44; John Bellamy Foster, Ecology Against Capitalism (New York: Monthly Review Press, 2002).
5. Metabolism-the relationship of interchange within and between nature and humans, of regulatory processes that govern the regeneration of a system-is a foundational concept in ecology. Marx used a metabolic approach for studying the environmental problems of his day, looking at the metabolism of natural systems. Whereas the metabolic rift was originally described in the context of agriculture and the soil crisis, we extend its usage to study the interaction between society and the oceans. Mészáros notes that each mode of production creates a particular social metabolic order, which can be characterized by the material interchange between society and nature. See Mészáros, Beyond Capital, 40-45; John Bellamy Foster, Marx's Ecology (New York: Monthly Review). This essay, here, draws upon our article, "The Metabolic Rift and Marine Ecology," Organization & Environment 18, no. 4 (2005): 422-44, in which we extend and develop in detail metabolic analysis as it relates to marine ecosystems.
6. Valiela, Marine Ecological Processes, 275.
7. Pew Ocean Commission, America's Living Oceans; Elisabeth Borgese, The Oceanic Circle (New York: United Nations University Press, 1998).
8. Farooq Azam, et al., "The Ecological Role of Water-Column Microbes in the Sea," Marine Ecology Progress, Series 10 (1983): 257-63; Valiela, Marine Ecological Processes.
9. James A. Estes, "Exploitation of Marine Mammals," Journal of the Fisheries Research Board of Canada 36 (1979): 1009-17; M. Omori, "Zooplankton Fisheries of the World," Marine Biology 48 (1978): 199-205.
10. Richard Ellis, The Empty Ocean (Washington, DC: Island Press, 2003), 13.
11. Mark Kurlansky, Cod (New York: Walker and Co., 1997), 138-39.
12. Northeast Fisheries Science Center, National Oceanic and Atmospheric Administration, accessed April 10, 2005, from Kurlansky, .
13. Today's trawlers now use technology developed by the military to fish waters as deep as one mile from the ocean's surface. They cost as much as $40 million to build, and they reach the length of a football field. There are currently over 37,000 industrial trawlers in the world's oceans, aiding in the total annual harvest of over 80 million tons of fish. See William Warner, Distant Water (Boston: Little, Brown and Company, 1983), viii.
14. Kurlansky, Cod.
15. Javier Perez de Cuellar, "International Law is Irrevocably Transformed," in United Nations, The Law of the Sea: Official Text of the United Nations Convention on the Law of the Sea with Annexes and Index, A/CONF.62/122 (New York: United Nations, 1983), xxix; Mike Skladany, Ben Belton, and Rebecca Clausen, "Out of Sight and Out of Mind: A New Oceanic Imperialism," Monthly Review 56, no. 9 (February 2005): 14-24.
16. Sharon Lafraniere,"Europe Takes Africa's Fish, and Boatloads of Migrants Follow," New York Times, January 14, 2008; Elisabeth Rosenthal, "Europe's Appetite for Seafood Propels Illegal Trade," New York Times, January 15, 2008; John W. Miller, "Offshore Disturbance: Global Fishing Trade Depletes African Waters," Wall Street Journal, July 18, 2007.
17. FOA, The State of World Fisheries and Aquaculture (Rome: FAO, 2004), 6, 123; FOA, The State of World Fisheries and Aquaculture 2006 (Rome: FOA, 2006), 3; Harrington, Myers, and Rosenberg, "Wasted Fishery Resources." Rebecca Clausen and Richard York, "Economic Growth and Marine Biodiversity," Conservation Biology 22 no. 2 (2008): 458-66; Jennifer A. Devine, Krista D. Baker, and Richard L. Haedrich, "Deep-Sea Fishes Qualify as Endangered," Nature 439 (2006): 29.
18. Richard Ellis, "The Bluefin in Peril," Scientific American (March 2008): 71-77.
19. Juliette Jowit, "Krill Fishing Threatens the Antarctic," Guardian, March 23, 2008.
20. Peter H. Tyedmers, Reg Watson, and Daniel Pauly, "Fueling Global Fishing Fleets," Ambio 34 no. 8 (2005): 635-38.
21. Valiela, Marine Ecological Processes; A. Lack, Katherine Short, and Anna Willcock, Managing Risk and Uncertainty in Deep-Sea Fisheries (Australia: World Wildlife Fund, 2003); Devine, Baker, and Haedrich, "Deep-Sea Fishes Qualify as Endangered."
22. Dayton L. Alverson and Steven E. Hughes, "Bycatch," Reviews in Fish Biology and Fisheries 6 (1996): 443-62; Larry B. Crowder and Steven A. Murawski, "Fisheries Bycatch," Fisheries 23 (1998): 8-16; Harrington, Myers, and Rosenberg, "Wasted Fishery Resources" Lance E. Morgan and Ratana Chuenpagdee, Shifting Gears (Washington, DC: Island Press, 2003); Dayton L. Alverson, Mark H. Freeberg, Steven A. Murawski, and J.G. Pope, "A Global Assessment of Fisheries Bycatch and Discard," FAO Fisheries Technical Paper 339 (Rome: FAO, 1996).
23. Harrington, Myers, and Rosenberg, "Wasted Fishery Resources," 358.
24. Valiela, Marine Ecological Processes, 514.
25. The concept of "fishing down the food chain" was first introduced in 1998. Since then it has received international attention. See Daniel Pauly, Villy Christensen, Johanne Dalsgaard, Rainer Froese, and Francisco Torres Jr., "Fishing Down Marine Food Webs," Science 279 (1998): 860-63.
26. In addition to fishing pressures, cod populations are confronting different environmental conditions, which are making population recovery difficult. Global warming is increasing the temperature of the oceans. A warm-water copepod plankton available in late summer has displaced the cold-water copepod plankton, which bloomed at the same time that baby cod needed such food. The shifts in plankton species due to the warming of the oceans has further complicated the conditions for cod to regenerate their numbers. Additional capture of cod in the North Sea could decimate the population to the point of no recovery. See Debora MacKenzie, "Cod Starved to Extinction," New Scientist 180 (2003): 8.
27. Jeremy B. Jackson, et al., "Historical Overfishing and the Recent Collapse of Coastal Ecosystems," Science 293 (2001): 629-37.
28. Jackson, et al., "Historical Overfishing," 631.
29. Carl Folke, et al., "Regime Shifts, Resilience, and Biodiversity in Ecosystem Management," Annual Review of Ecology, Evolution, & Systematics 35 no. 1 (2004): 557-81; O. Hoegh-Guldberg, et al., "Coral Reefs Under Rapid Climate Change and Ocean Acidification," Science 318 (2007): 1737-42.
30. Jackson, et al. "Historical Overfishing," 636.
31. Aquaculture can be broadly defined to include all historic forms of controlled rearing of aquatic organisms. For the purposes of this paper, we solely address capital intensive aquaculture of high trophic level species in the marine environment. For the remainder of the essay, the term "aquaculture" will only be referring to this contemporary form of capitalist aquaculture.
32. Snigda Prakash, "Soybean Industry Looking for Ways to Make Soy-based Food More Palatable to Farm-Raised Fish," National Public Radio, Morning Edition, May 26, 2004.
33. Edward Carr, "A Second Fall," The Economist 347 (1998): 3-4.
34. FOA, State of World Fisheries, 2002; FOA, The State of World Fisheries 2006, 3.
35. Rosamond L. Naylor, et al., "Nature's Subsidies to Shrimp and Salmon Farming," Science 282 (1998): 883-84.
36. Fred Magdoff, "A Precarious Existence," Monthly Review 55, no. 9 (February 2004): 1-14; Fred Magdoff, "The World Food Crisis," Monthly Review 60, no. 1 (May 2008): 1-15.
37. Naylor et al., "Nature's Subsidies."
38. Given the continual pressures placed on the fish stock in the oceans, compounded by the demands of aquaculture, capital is seeking out other forms of fishmeal as a substitute for marine derived protein sources. Corporations are working to modify soybeans as a fish feed substitute. See Prakash, "Soybean Industry Looking for Ways."
39. Don Staniford, "Silent Spring of the Sea," in Stephen Hume, et al., (eds.), A Stain Upon the Sea (Madeira Park, British Columbia: Harbour Publishing, 2004), 149; Ronald Hites, et al., "Global Assessment of Organic Contaminants in Farmed Salmon," Science 303 (2004): 226-29; Rachel Carson, Silent Spring (Boston: Houghton Mifflin, 1962).
40. Sea Grant News Media Center, "Bovine Hormone Could Provide Boost to Tilapia Aquaculture," http://www.seagrantnews.org/news/tips/tip_2003_feb.html; Thomas T. Chen, et al., "Transgenic Fish and Its Application in Basic and Applied Research," Biotechnology Annual Review 2 (1996): 205-36.
41. Naylor et al., "Nature's Subsidies."
42. Nils Kautsky, et al., "The Ecological Footprint," EC Fisheries Cooperation Bulletin 11, no. 3-4 (1998): 5-9.
43. Tyedmers, Watson, and Pauly, "Fueling Global Fishing Fleets."
44. Paul Burkett, "Natural Capital, Ecological Economics, and Marxism," International Papers in Political Economy 10, no. 3 (2003): 47; Paul Burkett, Marx and Nature (New York: St. Martin's Press, 1999).
45. Karl Marx, The Poverty of Philosophy (New York: International Publishers, 1971), 54.
46. Mészáros, Beyond Capital, 174; Foster, Ecology Against Capital.
47. Boris Worm, et al., "Impacts of Biodiversity Loss on Ocean Ecosystem Services," Science 314 (2006): 787-90.

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Monthly Review | The Oceanic Crisis: Capitalism and the Degradation of Marine Ecosystem

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Brett Clark teaches sociology at North Carolina State University in Raleigh. Rebecca Clausen teaches sociology at Fort Lewis College in Durango, Colorado. The world ocean covers approximately 70 percent of the earth. It has been an integral part of human history, providing food and ecological services.

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Did You Know?

Ringed seals live under solid sea ice by keeping breathing holes open with their claws.

General Description

Ringed seals are the smallest and the most abundant of the Alaska seals. Ringed seals live under solid sea ice by keeping breathing holes open with their claws. Ringed seals make snow caves (lairs) above some breathing holes to rest and give birth. During the breeding season, male ringed seal's faces turn black and they have a strong gasoline smell.

Ringed seals are the most common prey of polar bears; in fact, a polar bear may kill a ringed seal every 2 to 6 days. Ringed seals are also preyed upon by walruses and killer whales. Pups are eaten by polar bears, arctic foxes, red foxes, and ravens. Arctic foxes and polar bears can locate seal lairs by smell. During pupping, foxes will tunnel into the lairs to catch the pups. Polar bears will run and jump on the snow over the hole to collapse the lair and block the exit so it can catch the mother and the pup.

Life History

Growth and Reproduction

Females give birth to a single pup within a subnivean (snow covered) birth lair. Pups are born covered in lanugo, a coat of white wooly hair that insulates them until they can build fat reserves. Lanugo is shed at 2 to 3 weeks. The average weight of pups at birth is 10 pounds (4.5 kg). Females nurse pups for about two months and during that time the pup doubles its birth weight. Weaning usually takes place at ice breakup. Most females breed again within a month after giving birth. Implantation of the embryo is delayed until mid-July or early August so that pregnancy lasts about 11 months. Most female ringed seals first ovulate at 5-6 years of age and first give birth at 6-8 years. Males become sexually mature at the same age.

Breeding takes place in April to May. During this period rutting males exhibit territorial behavior and emit a strong scent from glands of their faces; due to their scent, hunters refer to them as "kerosene" or "gasoline seals" and avoid harvesting them because they do not taste good. Polar bears also avoid male ringed seals this time of year.

Feeding Ecology

Ringed seals are opportunistic and eat a variety of invertebrates, fish, and amphipods. The particular species eaten depends on availability, depth of water, and distance from shore. In Alaska waters, the important food species are arctic cod, saffron cod, shrimps, and other crustaceans.

Range and Habitat

Breeding ringed seals return to the same breeding territories in heavy shorefast ice each year while juvenile ringed seals migrate south to the ice edge for the winter, but it is unknown if young seals return to their birth region when they are old enough to breed. Ringed seals are also seen and harvested during ice-free periods in the Bering, Chukchi, and Beaufort seas. They often move long distances this time of year, but their movements are not well understood.

Status, Trends, and Threats

Status

Genetic studies have not delineated any stocks or separate populations and there are no reliable population estimates available for ringed seals. Numerous surveys have counted seals in portions of their range, but there is not enough information about movements and how to correct for the number of seals that were under the ice during the survey. Based upon these data, there are at least 250,000 ringed seals in Alaskan waters; the true number is probably much higher. Ringed seals were listed as 'threatened' under the Endangered Species Act (ESA). Worldwide, it is believed there are 6-7 million ringed seals.

NatureServe:
Global - G5 (Secure)
IUCN: Least concern
ESA: Threatened

Trends

Because there are no reliable population estimates there is also no trend information.

Threats

Because of their dependence on sea ice, there is concern that climate change may negatively affect ringed seals and their habitat. Changes in sea ice thickness, coverage, formation timing, and duration of coverage due to climate change may substantially alter the quality and amount of sea ice and snow necessary for resting, molting, and pupping. Activities associated with offshore oil exploration and recovery could affect ringed seal distribution and the prey they feed on. However, the effects of direct contact with oil and industrial disturbances on ringed seals have not been studied.

Fast Facts

Size
Average 4 feet, 120 pounds

Range/Distribution
Bering, Chukchi, and Beaufort seas in Alaska and circumpolar

Diet
Fish and invertebrates

Predators
Polar bears, killer whales, walruses, and Alaska Native hunters

Reproduction
One pup annually

Remarks
Co-managed by the National Marine Fisheries Service and the Ice Seal Committee

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ringed seal phoca hispida general description reproduction growth feeding eating behavior migration range habitat status trends threats facts information photo map audio

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Ringed Seal Species Profile, Alaska Department of Fish and Game

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Did You Know? Ringed seals live under solid sea ice by keeping breathing holes open with their claws. Ringed seals are the smallest and the most abundant of the Alaska seals. Ringed seals live under solid sea ice by keeping breathing holes open with their claws.

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The seals of Lake Baikal are a mystery (Photo: Getty)

Lake Baikal, near Russia's border with Mongolia, is, by volume, the biggest body of fresh water on Earth.

At 1.6km, it is also the deepest. Several unusual animals call it home, including the world's only species of freshwater seal.

Baikal's seals are abundant. There are about 100,000 of them. But the lake is nutrient-poor, so how they do so well has been a mystery. A study just published in the Proceedings of the National Academy of Sciences, by Watanabe Yuuki of the National Institute of Polar Research, in Tokyo, suggests the answer is by filtering tiny organisms from the water.

Most seals eat fish. And Baikal seals do, indeed, have needle-pointed canines of the sort expected of piscivores. But in 1982 researchers noted that they sport a second sort of specialised tooth behind those canines. These have frilled cusps which resemble combs. At the time, nobody knew what to make of them. But Dr Watanabe speculated that they might be an adaptation for feeding on other strange creatures dwelling in the lake.

Comb-like teeth

Seals arrived in Baikal two million years ago, from the Arctic Ocean. So too did some much smaller marine creatures, known as amphipods. These have diversified into more than 340 indigenous species. One of them, Macrohectopus branickii, spends its days hiding in the depths of the lake and then forages in the shallows at night in great numbers.

Marine mammals the size of seals would normally see amphipods as too small to hunt. But Dr Watanabe wondered if the Baikal seals' comb-like teeth might have evolved to enable them to rake these tiny crustaceans from the water in sufficient quantities to make them useful prey - much as some whales collect krill using comb-like structures called baleen plates.

He and his colleagues therefore attached waterproof video cameras and accelerometers to a few seals, to monitor what they were getting up to. This equipment remained attached to the animals for between two and four days, before coming loose and floating to the lake's surface, whence the researchers were able to recover it.

Parallel evolution

Footage from the cameras and data from the accelerometers showed that the seals were indeed pursuing the dense amphipod aggregations that form at night. They would dive in with their mouths open and collect prey before making another pass.

Dr Watanabe estimates that each seal captures an average of 57 amphipods per dive - and thus thousands of them a day. The needlelike canines are not redundant, for the seals do hunt fish as well. But they also compete with those fish for the amphipods, thus partially bypassing a link in the food chain and perhaps thereby maintaining themselves in larger numbers than would otherwise be possible.

Whether, were some of these filter-feeding seals to make it back to the ocean, they would follow the baleen whale path and evolve into giants, is an interesting speculation. But even confined to their lake, Baikal seals provide an intriguing example of parallel evolution.

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How the seal population of Lake Baikal grew to 100,000, despite the nutrient-poor waters

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Lake Baikal, near Russia's border with Mongolia, is, by volume, the biggest body of fresh water on Earth. At 1.6km, it is also the deepest. Several unusual animals call it home, including the world's only species of freshwater seal. Baikal's seals are abundant. There are about 100,000 of them.

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Social Structure

California sea lions do not have a stable social organization during the nonbreeding season (August through April).

California sea lions are extremely gregarious and form large aggregations when on land. Individuals lie close to each other, or even on top of each other.

Large male California sea lions exhibit size-related dominance over smaller animals.

When in the water, California sea lions often form small groups.

During the breeding season, California sea lions gather in rookeries for pupping and breeding.

Social Behavior

On land, sea lions aggregate in protected areas near shore.

In the water, they may form a raft: a small mass of sea lions on the surface in very close proximity.

Juvenile and nonbreeding California sea lions are perhaps the most playful of the otariids. They often ride the surf, chase each other, push and shove each other off rocks, and practice territorial battles. Adults engage in these activities less often.

In response to sudden or unusual activity (such as a loud noise or rapid movement), one or a few individuals start toward the water. This begins a rush as the rest of the herd follows. This alarm reaction is less pronounced during the breeding season.

Dominance behaviors are most aggressive during the breeding season. Males establish dominance by open-mouth threats and vocalizations, pushing, and shoving.

Territorial Behavior

Territorial behavior in males is strongly correlated to mating behavior. At the onset of the breeding season, male California sea lions establish breeding territories.

Dominant male California sea lions maintain territories from May through August, but territorial behavior is most intense between late June and early July. Galápagos sea lions maintain territories until January.

A male's territory extends beyond the water's edge and is partly aquatic. Various physiographic features (i.e. boulders, tide pools, reefs) serve as borders.

Boundaries are poorly defined and vary according to time of day, temperature, and movement of the females. Average size of a territory is about 130 square meters (1,400 square ft.). Males are frequently observed along the beach at 10-15 m (33-49 ft.) intervals.

Males establish territories by incessant barking, chest-to-chest pushing, grappling, and biting. Fights may result in injury, but are rarely fatal.

Once territories are established, males patrol their boundaries and bark when necessary to maintain and defend them. An intruding male evokes and immediate response from the resident male, who struggles violently to displace the intruder. To reaffirm their borders males often engage in ritualized boundary displays. One such display is when two bordering males rush at each other, barking. When they reach the border they stop barking, fall on their chests, and, with mouths open, shake their heads from side to side. They then rear up and stare obliquely at each other. Bull also patrol the aquatic borders of their territories by swimming along the territories' edges.

Territories exist only when and where females are present. Females, however, are relatively indifferent to the territories and move about freely between them. Males make no attempts to herd females or prevent their departure.

Individual Behavior

California sea lions often rest and sleep on land and in the water.

A sea lion may raise a flipper out of the water to regulate its body temperature.

Sea lions often "porpoise"; that is, they leap out of the water while swimming and re-enter headfirst.

Interaction With Other Species

California sea lions share haul-out space with northern elephant seals, harbor seals, northern fur seals, and Steller sea lions. California sea lions frequently interact with these species in much the same way as they interact among themselves.

California sea lions normally coexist peacefully with other marine mammal species, but breeding males, and females with newborn pups, may threaten and chase intruders. During breeding season, territorial disputes between male California sea lions and fur seals usually result in a victory for the more aggressive fur sea

Pups and juveniles may snap at and briefly chase gulls.

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California sea lions do not have a stable social organization during the nonbreeding season (August through April). California sea lions are extremely gregarious and form large aggregations when on land. Individuals lie close to each other, or even on top of each other. Large male California sea lions exhibit size-related dominance over smaller animals.

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The Black-chinned dolphin, or Peale's dolphin, are very interactive sea mammals, preferring curiosity towards boats and other sea creatures.

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Geographic Range

( Lagenorynchus australis lives mostly in the mildly cold and temperate waters off of South America and the Falkland Islands in the South Atlantic Ocean. One sighting has been reported near the Cook Islands also. Nowak, 1999; Reeder and Wilson, 1993)

Habitat

L. australis is usually found near the coast. These dolphins love to swim in and around the channels within kelp beds. They have also been sighted around sandbars and shallow bays. Most sightings of L. australis occur while there are strong tidal currents and during medium tides.

Peale's dolphins tend to inhabit two types of coastline. In the south they are usually found near channels and fjords. In the northern and eastern coast ranges, where the continental shelf underwater is very wide, they tend to be found in the open coast. In the open coast they have been found to swim as deep as 300 meters. There is little kelp there, but more southward and towards the Falkland Islands there are many kelp beds and this is where you will mostly find L. australis. ( de Haro and Iniquez, 1997; Goodall, et al., 1997a; Goodall, et al., 1997b; Lescrauwaet, 1997; Nowak, 1999; Reeder and Wilson, 1993)

Range depth

300 (high) m

984.25 (high) ft

Physical Description

L. australis has many distinguishing physical characteristics. Some of these include a torpedo shaped body, a dark gray back, a white belly, a light gray area on flanks that extends from behind to the anus and a skinny white band that begins behind the dorsal fin and gets wider as it extends backwards. This latter feature is termed the "tail stock".

L. australis has double black rings around both eyes and that extend forward to the nose. A final distinguishing feature that separates this species from other similar looking species is a circular patch of varying gray colors that is right on the thoracic area of the back.

The young of L. australis tend to look the same as the adults, but are much lighter in color. They become darker as they mature.

The teeth of L. australis seem to be variable. The maximum number on each upper jaw is thirty-seven and thirty-six on each lower jaw. Many teeth are hidden in the gums of the mouth.

The pectoral fin length is approximately 30 cm, and the dorsal fin can be up to 50 cm in height. The tail fluke is generally 30-60 cm wide, and the beak is up to 5 cm in length.

These animals may weigh up to 115 kg. ( de Haro and Iniquez, 1997; Goodall, et al., 1997a; MacDonald, 1984; Nowak, 1999)

Average mass

115 kg

253.30 lb

Range length

150 to 310 cm

59.06 to 122.05 in

Development

Very little has been recorded about the developmental cycle in L. australis. The only studies recorded represent measurements of the ovaries of a few female L. australis. These measurements were representative of the different sexual maturities and the data showed the older females as having more ovarian scars. Even less information has been gathered about males and their sperm activity. There was not enough conclusive information to make any statements. No information has been collected about the young in L. australis and there have been no specimens collected or found with a fetus inside. Because of this we are left to assume that this species is similar in the developmental patterns of better-known dolphin species.

(Goodall et al, 1997 and Claver et al, 1992)

Reproduction

Little is known bout the mating system of these animals.

In general it has been noted that species within the genus Lagenorynchus have gestation periods of ten to twelve months. Calving season for L. australis usually occurs between the southern spring and autumn but a calf can be born as early as October. Females tend to have only one calf per birth (maybe two) and they also move more inshore to do this. Some records show that when two of these dolphins were spotted together in the past, they were only considered a mother and calf if the smaller of the two animals was one third or less the size of the adult accompanying it. On visual sightings alone, this is probably still the most common way to tell a calf from an adult.

Although data are not available for this species, in another member of the genus, ( L. acutus, young are between 90 and 125 cm at birth. They nurse for about 18 months, and become independent of their mothers around the age of 2 years. It is not known whne these animals mature sexually. Goodall, et al., 1997a; Goodall, et al., 1997b; Nowak, 1999)

Breeding season

It is not known for certain when mating occurs, but births occur during the Southern Spring to Autumn.

Range number of offspring

1 to 2

Average number of offspring

1

Range gestation period

10 to 12 months

Young are precocial and swim along side of their mothers from birth. The mother provides her calf with milk for approximately 18 months, although the calf may remain dependent upon her for an additional 6 months. It is not known what role males play, if any, in the parental care of this species. ( Nowak, 1999; Nowak, 1999)

precocial

pre-hatching/birth

pre-weaning/fledging

pre-independence

extended period of juvenile learning

Lifespan/Longevity

Scientists are able to determine the age of Peale's dolphins by looking at their teeth but no records or studies explain how this is accomplished. The oldest recorded specimen of L. australis was thirteen years old. ( Goodall, et al., 1997a; Goodall, et al., 1997b)

Range lifespan
Status: wild

13 (high) years

Behavior

L. australis display many different types of behavior. When swimming L. australis is known for jumping, humping, spinning, and tailslapping. Some tail slaps are believed to aid foraging by directing fish towards other dolphins.

These animals tend to be gregarious and swim in small groups from 1 to 13 individuals. Most sightings are of groups with 2 to 4 members. In the summer months the average group size is 2 members. Some groups as large as 100 members have been recoreded. When such large aggregations occur, the dolphins tend to divide themselves up into sub-groups. Larger groups tend to be sighted more often in the months of January and February.

When swimming L. australis will surface about three to four times per minute and dive between one and 130 seconds. The average dive lasts less than 60 seconds.

The young have been seen surfacing a few more times a minute than the adults. When coming up from a dive, they expose only their blowhole and a part of the dorsal fin. Groups tend to surface together as if in some sort of rhythmic pattern.

When swimming rapidly Peale's dolphins display a behavior where water splashes up high around their faces, and they have accordingly been nicknamed "plow share dolphins".

When floating these animals tend to lay on their sides so they can look up at the boats around them. L. australis is very social around all kinds of boats and are often seen playing or swimming around them.

Individuals often follow in the wake of a boat, but once the propeller is turned off the dolphins' interest seems to subside.

L. australis has been known to interact with many species of ocean life including the following:

Commerson's dolphins (Cephalorynchus commersoni)

Southern right whales ( Eubalaena australis)

Great grebes ( Podiceps major)

Megellanic penguins ( Spheniscus magellanicus)

Kelp gulls ( Phalacrocorax magellanicus and Larus dominicanus)

South American sea lions ( Otaria flavescens and Otaria flavescens)

Imperial shags ( Phalacrocorax atriceps)

Rissos dolphins ( Grampus griseus).

Many of these interactions are for playful purposes but some are for the sole purpose to help them catch their food. ( de Haro and Iniquez, 1997; Goodall, et al., 1997a; Goodall, et al., 1997b; Nowak, 1999; Schiavini, et al., 1997)

Home Range

The home range size of these animals has not been reported.

Communication and Perception

Sounds emitted under water by L. australis include low frequency clicking noises and a "rapid tonal sound", but no whistling. There is little research on vocalizations, as they seem to be very timid communicators around boats taking the data. ( Goodall, et al., 1997a; Goodall, et al., 1997b)

Food Habits

Peale's dolphins may feed in groups or alone. It has been hypothesized that this species may tend to feed alone when food is scarce and in groups when food is of abundance. When in groups, L. australis usually exhibits what is called "flower" or "starburst" feeding. They encircle their prey until they form a large group and then they feast. This is mostly done within the kelp beds. When they are sighted eating alone it is usually close to shore. When diving for prey it has been reported that they stay under water from between 10.36 seconds to 1.46 minutes.

Not very many L. australis have been dissected for examining the stomach contents, but known prey species are very extensive all the same.

Foods eaten include: ( Pleoticus muelleri (Argentine shrimp), squid ( Loligo gahi and Illex argentinus), Kingklip fish ( Genypterus blacodes), Argentine hake ( Merluccius hubbsi), southern cod ( Salilota australis), hagfish ( Myxine australis), Pantagonian grenadier ( Marcuronus magellanicus), red octopus ( Enteroctopus megalocyathus), other species of herring, makarel, capelin, anchovies, crustaceans and whelks (gastropods). de Haro and Iniquez, 1997; Nowak, 1999; Schiavini, et al., 1997)

fish

mollusks

aquatic or marine worms

aquatic crustaceans

Predation

There are no known predators of L. australis.

Ecosystem Roles

There is so little known about Peales dolphins that their effect on the pelagic ecosystem is unknown. However, because they prey upon a number of types of animals, there is a potential impact of these dolphins upon prey populations. ( Goodall, et al., 1997a; Goodall, et al., 1997b)

Economic Importance for Humans: Positive

Humans have occasionally harpoon Peales dolphins for use as bait. ( Goodall, et al., 1997a; Goodall, et al., 1997b)

Economic Importance for Humans: Negative

It is difficult to speculate on how these acquatic mammals might negatively impact humans. There are no reports of negative interactions, but it is possible that through their predatory behavior, populations of Peale's dolphins could negatively impact commercial or subsistence fisheries. However, this is just speculation, and there are no reports of this being the case.

Conservation Status

Lagenorynchus australis has not been studied intensively to determine population trends. There are a few human sources of mortality that may be of a concern in the future. These include shore-set gill nets (accidental catch), inshore fishing (incidental catch), and salmon farms near Chile (a few have been caught in the anti-pinniped nets despite the loud sounds made underwater to deter them). Deep sea fishermen have been known to occasionally catch a few Peales dophins in their mid-water nets. A more serious situation is occurring near crab fisheries where the use of nets has been outlawed. Fisheries have been known to use harpooned L. australis as bait. (Nowark, 1999 and Goodall et al, 1997)

There are many other common names for this species beside the common name Peales dolphin. These are Peales Porpoise, black-chinned dolphin, and Southern white-sided dolphin. In Spanish it used to be called llampa or tunina in Chile. Now it is called delfin austral (southern dolphin) in Chile and Argentina.

(Goodall et al, 1997)

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Heather Floyd (author), California State University, Sacramento, James Biardi (editor), California State University, Sacramento.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

Neotropical

living in the southern part of the New World. In other words, Central and South America.

References

Claver, J., M. Iniguez, D. Lombardo, I. von Lawzewitsch. 1992. Preliminary Observations on Ovarian Activity and Sexual Maturity in Female Peale's Dolphin (Lagenorynchus australis). Aquatic Mammals, 18: 85-88.

Goodall, R., K. Norris, W. Schevill, F. Fraga, R. Praderi. 1997. Review and Update on the Biology of the Peale's Dolphin, Lagenorynchus australis. International Whaling Commission Report, 47: 777-796.

Goodall, R., J. de Haro, F. Fraga, M. Iniquez, K. Norris. 1997. Sightings and Behavior of Peale's Dolphins, Lagenorynchus australis, with Notes on Dusky Dolphins, L. obscurus, off Southern Most South America. International Whaling Commission Report, 47: 757-775.

Lescrauwaet, A. 1997. Notes on the Behavior and the Ecology of the Peale's Dolphin, Lagenorynchus in the Strait of Magellan, Chile. International Whaling Commission Report, 47: 747-755.

MacDonald, D. 1984. Encyclopedia of Mammals. N.Y.: Facts on File Publications.

Nowak, R. 1999. Walkers Mammals of the World, Sixth ediition. Baltimore and London: Johns Hopkins University Press.

Reeder, D., D. Wilson. 1993. Mammal Species of the World ed. 2. Washington and London: Smithsonian Institution Press.

Schiavini, A., R. Goodall, A. Lescrauwaet, M. Koen Alonso. 1997. Food Habits of the Peale's Dolphin, Lagenorynchus australis; Review and New Information. International Whaling Commission Report, 47: 827-834.

de Haro, J., M. Iniquez. 1997. Ecology and Behavior of the Peale's Dolphin, Lagenorynchus australis (Peale, 1848), at Cabo Virgenes (52 degrees 30' S., 68 degees 28'W), in Patagonia, Argentina. International Whaling Commission Report, 47: 723-727.

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( Lagenorynchus australis lives mostly in the mildly cold and temperate waters off of South America and the Falkland Islands in the South Atlantic Ocean. One sighting has been reported near the Cook Islands also. Nowak, 1999; Reeder and Wilson, 1993) L. australis is usually found near the coast.

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The Indus River dolphins' population rose thanks to the help of local communities.

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Indus river dolphin numbers have increased dramatically over the past 16 years, thanks largely to successful community-based conservation efforts.

A new WWF survey says there are now an estimated 1,816 Indus river dolphins in Pakistan-almost 50% more than the 1,200 dolphins estimated during the first comprehensive census in 2001 when the species appeared to be on the brink of extinction.

"Significantly increasing the number of Indus river dolphins over the past 15 years is a remarkable achievement considering the ever-increasing pressure on the river and the species," said Hammad Naqi Khan, director general of WWF-Pakistan. "And it shows that progress is possible when governments, conservationists, and communities work together."

The survey ran from March 20 to April 13 during low water season when the dolphins are most concentrated and easiest to count. A team of 20 scientists and researchers from WWF-Pakistan, Zoological Survey of Pakistan, and provincial wildlife departments, academia canvased the Indus river dolphin range. Except for a tiny, isolated population of about 30 in India's Beas River, Indus river dolphins live exclusively in the Indus river in Pakistan.

A species in need
Even with the welcomed bump in population numbers, Indus river dolphins remain endangered and in need of continued conservation action. Currently confined to just 20% of their natural habitat range due to the construction of numerous dams and barrages along the Indus River, the dolphins are also threatened by worsening water pollution, stranding in irrigation canals, and accidental capture in fishing nets.

WWF has led an innovative and collaborative approach to save the species, integrating research, effective law enforcement, and critical community engagement. Since 1992, WWF-Pakistan and the Sindh Wildlife Department have led a dolphin rescue program, which has saved 131 dolphins from being stranded in irrigation canals and safely released them back into the main river. We've also established a dolphin monitoring network in collaboration with local communities, Sindh Wildlife Department and other important government stakeholders , along with a 24-hour phone helpline that people can call if they see a dolphin in distress.

"Indus river dolphin numbers would still be decreasing if it were not for the active participation of communities along the river," Khan said. "They are our eyes and ears, and have helped bring these iconic animals back from the brink. Our efforts to save the dolphin are also critical for these communities since the species is an indicator of the health of the river, upon which tens of millions of people depend."
Learn more about Indus river dolphins.

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Indus river dolphin numbers on the rise with the help of local communities

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Indus river dolphin numbers have increased dramatically over the past 16 years, thanks largely to successful community-based conservation efforts. A new WWF survey says there are now an estimated 1,816 Indus river dolphins in Pakistan-almost 50% more than the 1,200 dolphins estimated during the first comprehensive census in 2001 when the species appeared to be on the brink of extinction.

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Pacific White-Sided dolphins prefer to interact with a mixed group of sea species, including other dolphins.

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Geographic Range

Pacific white-sided dolphins, Lagenorhynchus obliqiudens, can be found throughout the temperate waters of the northern Pacific Ocean. This pelagic species is endemic to the cold regions of the Pacific, most commonly occurring between the latitudes of 38 degrees N and 47 degrees N. The species in not found in arctic and tropical waters.

They also range in the western Pacific Ocean from the South Bering Sea to southern Japan.

White-sided dolphins are found along the west coast of North America, and migrate seasonally in north-south (latitudinal) directions. These dolphins are most abundant in shelf waters off southern California during the winter and off Oregon and Washington during late spring. Historically, Pacific white-sided dolphins have been observed as far south as the Gulf of California. In recent years, Lagenorhynchus obliqiudens has declined in the Gulf of California as water temperatures have increased. ( Salvadeo, et al., 2010; Stewart, et al., 2002)

Habitat

Pacific white-sided dolphins are common in temperate seas. They are most abundant in deeper waters in the open ocean and can dive as deep as 1000 m. Pacific white-sided dolphins exploit a large habitat including open ocean and near-shore waters. ("Food of the Pacific white-sided dolphin, Lagenorhynchus obliquidens, Dall's porpoise, Phocoenoides dalli, and northern fur seal, Callorhinus ursinus, off California and Washington, with appendices of size and food of Dall's porpoise from Alaskan waters", 1980; Black, 1994; Brown and Norris, 1956; Rechsteiner, et al., 2013; Ridgway and Harrison, 1998; Salvadeo, et al., 2010)

Range depth

0 to 1000 m

0.00 to 3280.84 ft

Physical Description

Pacific white-sided dolphins have a complex color pattern. They are black or dark gray with distinct light gray stripes on their sides, dorsal fin, and flippers. The stripes on their sides begin on the side of the face ahead of the eye and extend to the base of the tail. A large patch of light gray dominates the anterior of the dorsal fin. Their eyes and mouth have dark coloration. Distinguishing features of Pacific white-sided dolphins are their tall, hooked, bicolored dorsal fins, located at the center of their back. Pacific white-sided dolphins have pectoral fins that share the same coloration and are rounded.

White-sided dolphins are 1.7-2.5 m long, with an average of 2.0 m. Males can reach this length of 2.5 m while females can reach just 2.3 m. Adult white-sided dolphins typically weigh about 135-180 kg but males can weigh up to 200 kg. Newborn Pacific white-sided dolphins are 0.9-1.05 m long and weigh approximately 15 kg.

The bodies of Pacific white-side dolphins are robust, and torpedo-shaped. Pacific white-sided dolphins have 21 to 33 pairs of slightly-pointed teeth per jaw. Pacific white-sided dolphins have short beaks. Their skulls have an average length of 39 cm. ("Food of the Pacific white-sided dolphin, Lagenorhynchus obliquidens, Dall's porpoise, Phocoenoides dalli, and northern fur seal, Callorhinus ursinus, off California and Washington, with appendices of size and food of Dall's porpoise from Alaskan waters", 1980; Brown and Norris, 1956; Marino, 1999; Nowak, 2003; Prevost, 1996; Rechsteiner, et al., 2013; Ridgway and Harrison, 1998; Stewart, et al., 2002)

Range mass

78 to 200 kg

171.81 to 440.53 lb

Range length

1.7 to 2.5 m

5.58 to 8.20 ft

Average length

2.0 m

6.56 ft

Reproduction

Pacific white-sided dolphins breed seasonally from August to October. Although very little is known about their mating system, Connor (1994) suggests it is unlikely they are monogamous. ( Black, 1994; Connor, 1994; Ferrero and Walker, 1996; Stewart, et al., 2002)

The gestation period of Pacific white-sided dolphins lasts for 9-12 months. Most calving occurs during late spring and summer, and just one offspring is born. Pacific white-sided dolphins are 0.9 m-1.5 m in length at birth. Calves weigh, on average, 15 kg (range 13-22 kg) when born, and nurse for up to 18 months after birth. Pacific white-sided dolphins give birth at a minimum of once every two years.

Female Pacific white-sided dolphins reach sexual maturity around a length of 1.7 m and between the ages of 8 and 10 years. Males reach sexual maturity at lengths around 1.7-1.8 m between the ages of 10 and 11 years. Like other mammals, fertilization occurs internally. Pacific white-sided dolphins give birth to relatively well-developed young. ( Black, 1994; Ferrero and Walker, 1996; Mann, 2000; Nowak, 2003; Rechsteiner, et al., 2013; Salvadeo, et al., 2010; Stewart, et al., 2002)

Average number of offspring

1

AnAge

A Pacific white-sided dolphin calf stays with its mother until it reach independence around 18 months. Males are not involved in parental care beyond the mating process. ( Ferrero and Walker, 1996; Mann, 2000)

Lifespan/Longevity

Weigl (2005) estimates Pacific white-sided dolphins can live up to 46 years in captivity. Wilson and Ruff (1999) reported a captive Pacific white-sided dolphin lived to be 36 years. It is unknown how long they can live in the wild. ( Weigl, 2005; Wilson and Ruff, 1999)

Range lifespan
Status: captivity

46 (high) years

Typical lifespan
Status: captivity

36 (high) years

Behavior

Pacific white-sided dolphins are mobile creatures specialized for swimming. They can be found in groups ranging from just a few individuals to 100 individuals. These groups are sometimes separated into smaller subgroups or pods, which average about 15 members (typically 10 to 25). Pods consist of all ages and both sexes.

Pacific white-sided dolphins are social animals. They are often found in mixed-species aggregations with other cetaceans, pinnipeds, and sea birds. They associate most often with northern right whale dolphins ( Lissodelphis borealis) and Risso's dolphins ( Grampus griseus).

Pacific white-sided dolphins are active at the water's surface. They are known to ride the bow waves of ships. Pacific white-sided dolphins are also well known for their aerial displays. They leap clear of the water, and are the only dolphins of the eastern Pacific known to turn complete somersaults under natural conditions. ( Black, 1994; Dahlheim, et al., 2009; Nowak, 2003; Ridgway and Harrison, 1998; Stewart, et al., 2002)

Home Range

Generally, most pelagic mammals will not defend or use a home range. No home range has been reported and it's assumed Pacific white-sided dolphins do not have one.

Communication and Perception

Lagenorhynchus obliquidens uses echolocation clicks that range primarily from 20 to over 100 kHz. A study performed on captive Pacific white-sided dolphins revealed they use echolocation clicks and touch to interpret their surroundings. Pacific white-sided dolphins also produce whistle vocalizations, similar to other dolphins, in order to communicate with one another. They communicate visually, acoustically, and through touch. According to Henderson (2010) Pacific white-sided dolphin vocalizations differ across behavioral states. ("Food of the Pacific white-sided dolphin, Lagenorhynchus obliquidens, Dall's porpoise, Phocoenoides dalli, and northern fur seal, Callorhinus ursinus, off California and Washington, with appendices of size and food of Dall's porpoise from Alaskan waters", 1980; Baird, 1998; Black, 1994; Henderson, 2010; Ridgway and Harrison, 1998; Yeater, et al., 2014)

Food Habits

Pacific white-sided dolphins are versatile and opportunistic feeders. Their carnivorous diet consists of small fish found in large schools and squid ( Loligo). They typically consume Pacific herring ( Clupea pallasii), capelin ( Mallotus villosus), market squid ( Loligo opalescens), Pacific sardines ( Sardinops sagax) and mackerel ( Scomber japonicus) when available. An average-sized Pacific white-sided dolphin needs to consume around 12.5-15.8 kg of fish per day or approximately 16-20% of its body mass daily.

Lagenorhynchus obliquidens has been observed feeding in groups averaging in size from 11-50 individuals. They forage while simultaneously milling. They are not considered deep divers and typically feed close to the shelf in shallow depths. ("Food of the Pacific white-sided dolphin, Lagenorhynchus obliquidens, Dall's porpoise, Phocoenoides dalli, and northern fur seal, Callorhinus ursinus, off California and Washington, with appendices of size and food of Dall's porpoise from Alaskan waters", 1980; Black, 1994; Brown and Norris, 1956; Dailey, et al., 1993; Rechsteiner, et al., 2013; Ridgway and Harrison, 1998; Stewart, et al., 2002)

Predation

Due to their harmful effects on fisheries, humans ( Homo sapiens) kill Pacific white-sided dolphins. In regions of Japan, they are hunted for their meat. Killer whales (Orchinus orca) are also known predators of Lagenorhynchus obliquidens. Both humans and killer whales are predators of adult and young Pacific white-sided dolphins.

The coloration of Pacific white-sided dolphins allows them to be camouflaged. By having a light colored underside and a dark colored back, Pacific white-sided dolphins can blend in with their surroundings when being viewed by a predator from both above and below. ( Black, 1994; Nowak, 2003; Stewart, et al., 2002)

Ecosystem Roles

Pacific white-sided dolphins have a vital ecosystem role as consumers of fish. Seabirds often follow Pacific white-sided dolphins and consume fish the dolphins do not eat.

They are hosts for internal parasites including: nematodes ( ( Anisakis simplex and Crassicauda), trematodes ( Nasitrema globicephalae), and cestodes ( Phyllobothrium delphini, Monorygma grimaldii, and Strobilocephalus triangularus). They are also hosts for external parasites called cirripedes ( Xenobalanus). Dailey and Walker, 1978; Martin, et al., 1970; Nowak, 2003; Stewart, et al., 2002)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Pacific white-sided dolphins are hunted for their meat by Japanese fishermen. They are important in the entertainment and tourism industry. For example, these dolphins are trained in marine mammal parks to perform tricks and are used to educate attendees about dolphins. It is also common for Pacific white-sided dolphins to be spotted during whale-watching expeditions. ( Nowak, 2003; Stewart, et al., 2002)

Economic Importance for Humans: Negative

Pacific white-sided dolphins negatively affect commercial fisheries. They compete with the fisheries for fish and often become tangled in driftnets. ( Nowak, 2003; Stewart, et al., 2002)

Conservation Status

The greatest threat to Pacific white-sided dolphins is high-seas driftnets used by commercial fisheries. The United Nations' prohibition of high-seas driftnet fishing is the most significant attempt to conserve Pacific white-sided dolphins internationally. The United States requires fisheries in the Pacific to have acoustic warning signals to help prevent dolphins from being caught in driftnets. Although these signals have decreased the number of dolphins killed by driftnets, an average of 5.9 Pacific white-sided dolphins are caught and killed annually. Still, this is an improvement from historical deaths; Hobbs and Jones (1993) reported approximately 100,000 Pacific white-sided dolphins were killed between 1970 and 1990 by high-seas driftnet.

Pacific white-sided dolphins are harpooned in areas of Japan for human consumption. Although specific numbers are unknown, it is likely impact on Pacific white-sided dolphins due to Japanese harpooning is nominal.

Pacific white-sided dolphins are an Appendix II species, according to CITES. Per this Appendix, permits are required to trade Pacific white-sided dolphins internationally. Permits are only granted if the trade will not be detrimental to the survival of the species. Pacific white-sided dolphins are not threatened, but if current trade policies remain they could become endangered. The IUCN Red List lists Pacific white-sided dolphins as a species of "least concern." Lagenorhynchus obliquidens has no special status according to the US Federal List and the State of Michigan list. ( Hammond, et al., 2012; Hobbs and Jones, 1993)

Contributors

Taylor Layton (author), Radford University, Karen Powers (editor), Radford University, April Tingle (editor), Radford University, Emily Clark (editor), Radford University, Cari Mcgregor (editor), Radford University, Jacob Vaught (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

References

National Oceanic and Atmospheric Administration. Food of the Pacific white-sided dolphin, Lagenorhynchus obliquidens, Dall's porpoise, Phocoenoides dalli, and northern fur seal, Callorhinus ursinus, off California and Washington, with appendices of size and food of Dall's porpoise from Alaskan waters. 86137. Seattle, Washington: NOAA, NMFS. 1980.

Baird, R. 1998. An interaction between Pacific white-sided dolphins and a neonatal harbor porpoise. Mammalia, 62/1: 129-133.

Black, N. 1994. Behavior and Ecology of Pacific White-Sided Dolphins (Lagenorhynchus obliquidens) in Monterey Bay, California (Thesis). San Francisco, California: San Francisco State University.

Brown, D., K. Norris. 1956. Observations of captive and wild cetaceans. Journal of Mammalogy, 37/3: 311-326.

Connor, R. 1994. The Lives of Whales and Dolphins. New York: Henry Holt and Company.

Dahlheim, M., P. White, J. Waite, G. Eckert. 2009. Cetaceans of southeast Alaska: Distributional and seasonal occurrence. Journal of Biogeography, 36/3: 410-426.

Dailey, M., D. Reish, J. Anderson. 1993. Ecology of the Southern California Blight: A Synthesis and Interpretation. Oakland, CA: University of California Press.

Dailey, M., W. Walker. 1978. Parasitism as a factor (?) in single strandings of southern California cetaceans. The Journal of Parasitology, 64/4: 593-596.

Ferrero, R., W. Walker. 1996. Age, growth, and reproductive patterns of the Pacific white-sided dolphin (Lagenorhynchus obliquidens) taken in high seas drift nets in the central North Pacific Ocean. Canadian Journal of Zoology, 74/9: 1673-1687.

Gibbons, E., B. Durrant, J. Demarest. 1995. Conservation of Endangered Species in Captivity: An Interdisciplinary Approach. New York: SUNY Press.

Hammond, P., G. Bearzi, A. Bjørge, K. Forney, L. Karkzmarski, T. Kasuya, W. Perrin, M. Scott, J. Wang, R. Wells, B. Wilson. 2012. "Lagenorhynchus obliquidens" (On-line). The IUCN Red List of Threatened Species. Accessed March 27, 2015 at http://www.iucnredlist.org/details/11145/0.

Hayssen, V., A. Tienhoven. 1993. Asdell's Patterns of Mammalian Reproduction: A Compendium of Species-specific Data. New York: Cornell University Press.

Henderson, E. 2010. Cetaceans in the Southern California Bight: Behavioral, Acoustic, and Spatio-temporal Modeling (Thesis). San Diego, CA: University of California.

Hobbs, R., L. Jones. 1993. Impacts of high seas driftnet fisheries on marine mammal populations in the North Pacific. International North Pacific Fisheries Commission Bulletin, 53/3: 409-434.

Mann, J. 2000. Cetacean Societies: Field Studies of Dolphins and Whales. Chicago, Illinois: University of Chicago Press.

Marino, L. 1999. Brain growth in the harbor porpoise and Pacific white-sided dolphin. Journal of Mammalogy, 80/4: 1353-1360.

Martin, W., C. Haun, H. Barrows, H. Cravioto. 1970. Nematode damage to brain of striped dolphin, Lagenorhynchus obliquidens. Transactions of the American Microscopical Society, 89/2: 200-205.

Nowak, R. 2003. Walker's Marine Mammals of the World. Maryland: The Johns Hopkins University Press.

Prevost, J. 1996. White-Sided Dolphins. Minnesota: ABDO Publishing Company.

Rechsteiner, E., D. Rosen, A. Trites. 2013. Energy requirements of Pacific white-sided dolphins (Lagenorhynchus obliquidens) as predicted by a bioenergetic model. Journal of Mammalogy, 94/4: 820-832.

Ridgway, S., R. Harrison. 1998. Handbook of Marine Mammals: The Second Book of Dolphins and the Porpoises. Amsterdam, the Netherlands: Elsevier BV.

Salvadeo, C., D. Lluch-Belda, A. Gomez-Gallardo, J. Urban-Ramirez, C. MacLeod. 2010. Climate change and a poleward shift in the distribution of the Pacific white-sided dolphin in the northeastern Pacific. Endangered Species Research, 11/1: 13-19.

Stewart, B., P. Clapham, J. Powell, R. Reeves. 2002. Guide to Marine Mammals of the World. New York: Knopf Doubleday Publishing.

Weigl, R. 2005. Longevity of Mammals in Captivity: from the Living Collections of the World: A List of Mammalian Longevity in Captivity. Stuttgart, Germany: E. Schweizerbart'sche.

Wilson, D., S. Ruff. 1999. The Smithsonian Book of North American Mammals. Canada: UBC Press.

Yeater, D., H. Hill, N. Baus, H. Farnell, S. Kuczaj. 2014. Visual laterality in belugas (Delphinapterus leucas) and Pacific white-sided dolphins (Lagenorhynchus obliquidens) when viewing familiar and unfamiliar humans. Animal Cognition, 17/6: 1245-1259.

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Pacific white-sided dolphins, Lagenorhynchus obliqiudens, can be found throughout the temperate waters of the northern Pacific Ocean. This pelagic species is endemic to the cold regions of the Pacific, most commonly occurring between the latitudes of 38 degrees N and 47 degrees N. The species in not found in arctic and tropical waters.

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A group of Pantropical Spotted and Bottlenose dolphins traveling together as a form of collaboration.

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Bottlenose and pantropical spotted dolphins off Lāna‘i

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An ancestor of the South Asian River Dolphin gives clues to the practice behind the species' sideways swimming skills and a key to them and their subspecies' survival.

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What swims on its side, is blind, and lives in some of the most polluted rivers in the world?

Unlike the more than 30 species of oceanic dolphins, the South Asian River Dolphin is unique, or "tremendously bizarre" as Smithsonian marine mammal fossil curator Nicholas Pyenson puts it. But because of its polluted habitat, overfishing and other human-caused environmental pressures, the already rare dolphins are endangered.

But a new find hiding in the 40-million-specimen Smithsonian paleobiology collection may hold some clues about how to best protect this unique cetacean by uncovering its evolutionary past.

The new findings by Pyenson and researcher Alex Boersma show that a skull found in southeast Alaska by a United States Geological Survey geologist in 1951, is a new genus and species of dolphin that lived in subarctic ocean waters around 25 million years ago. Arktocara yakataga is one of the closest relatives to the modern South Asian River Dolphin.

An ancient relative

This artistic rendition shows what the new dolphin species Arktocara yakataga may have looked like 25 million years ago. The species has been found to be a close relative of the modern South Asian River Dolphins, only found in India, Nepal, Bangladesh, and Pakistan.

Yet Arktocara yakataga is not the only species to be found that is closely related to the South Asian River Dolphin, or Platanista gangetica. Many similar species once swam around the world, though the remnants can now only be found in the fossil record, and in their present day freshwater descendants.

"All the other twigs of the tree are dead, and this is the only one that's survived," says Pyenson.

Pyenson believes that more study, and new finds like this one, could help the current species, which only lives in rivers in the South Asian subcontinent. Once considered two species, the Indus river dolphin and the Ganges river dolphin are now considered subspecies of Platanista. There are less than 2,000 in the world.

The modern counterpart

The Indus River Dolphin, with the Ganges River Dolphin, are the two sub-species of South Asian River Dolphins, which are considered modern-day relatives of the new fossil find, Arktocara yakataga.

"Knowing more about the history could help us to better be able to make priorities in modern times," says Pyenson. Understanding why these toothed dolphins were "supplanted by ocean dolphins," dwindling down to one species, could change our conservation techniques for the better, he says.

Pyenson says that it is a possibility that the other similar species did not have the same echolocation sensibilities that have allowed Platanista to survive. Or they could have just been outcompeted by modern oceanic dolphins.

Whatever the reasons for the ancient extinctions may be, more research could bring hope for this modern species that is inching toward extinction. The past may be a window for the future.

A new find

This skull of Arktocara yakataga was found within the Smithsonian's paleobiology collection, which holds 40 million specimens.

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Fossil Discovery Could Help Today's Endangered River Dolphins

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What swims on its side, is blind, and lives in some of the most polluted rivers in the world? Unlike the more than 30 species of oceanic dolphins, the South Asian River Dolphin is unique, or "tremendously bizarre" as Smithsonian marine mammal fossil curator Nicholas Pyenson puts it.

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Through their DNA, Clymene Dolphins genetically recall their own hybrid origins.

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A well-known dolphin species, the clymene dolphin, arose from mating between two separate and distinct dolphin species, report genetics researchers.

Also known as the "short-snouted spinner dolphin," the clymene dolphin (Stenella clymene) grows to nearly seven feet (2.1 meters) long and dwells in deep waters in tropical and temperate parts of the Atlantic Ocean.

Evolutionary biologists have seen other such hybrid species elsewhere in the animal kingdom. The new discovery, reported in the journal PLOS ONE by a team led by marine biologist Ana Amaral of Portugal's University of Lisbon, adds to increasing evidence of such cross-breeding commonly leading to new species, even in the wide-open oceans.

Clymene dolphins feed mostly at night when squid and fish come to the surface of the water. The short-snouted dolphin gets its name from the ocean nymph Clymene of Greek mythology. (See "Dolphins Have 'Names,' Respond When Called.")

Researchers initially thought the clymene dolphin was a subspecies of the spinner dolphin (Stenella longirostris). However, in 1981, a closer look at the clymene's anatomy revealed it was a distinct species.

But experts remained uncertain about the clymene's relationship with its close relatives. Although its outward appearance and behavior are more similar to those of the spinner dolphin, its skull features closely resemble those of the striped dolphin (Stenella coeruleoalba).

DNA Analysis

To help solve this mystery, the study scientists analyzed skin samples from 15 clymene dolphins, as well as from 21 spinner and 36 striped dolphins. They collected the DNA from free-ranging dolphins-using special tissue-collecting darts-and from dead, stranded dolphins.

The investigators looked at nuclear DNA, which is found in the cell's nucleus and comes from both the mother and father, as well as DNA from their mitochondria-the cell's powerhouse-which possesses its own genes and is passed down solely from the mother.

"When I was first analyzing the data I collected, it was very confusing," said Amaral.

That's because Amaral and colleagues discovered that while the nuclear DNA of the clymene dolphin most resembled that of the spinner dolphin, the mitochondrial DNA was most similar to that of the striped dolphin. (See pictures of other hybrid animals.)

This is strong evidence that the clymene dolphin is a naturally occurring hybrid of the spinner and striped dolphins, said Amaral. Continued hybridization may still occur between the clymene dolphin's parent species, although at low levels, the study authors added.

The birth of a new species, known as speciation, is often thought to happen when one species splits into two or more isolated populations that diverge as they amass differences over time due to a lack of interbreeding.

Hybrids are usually infertile, with the mule-a cross between a male donkey and a female horse-being the most familiar example of this.

Hybrid Species: How Rare?

Past studies have shown that hybridization could occasionally lead to fertile offspring and even new species in plants, fishes, insects, and birds.

To get a hybrid species, two things need to occur, said evolutionary ecologist Pamela Willis at the University of Victoria in Canada, who did not take part in the study.

"You need to have hybrids be as fit as the parental species, able to carve out their own ecological space," she explained.

Then they somehow have to mate with only each other, rather than with either parental species, "hence allowing them to spin off onto their own, independent evolutionary trajectory and become a species of their own," Willis added. "Both of these conditions are hard to meet."

Scientists had thought hybrid speciation was exceptionally rare in mammals. "Mammals generally are less capable than other types of animals to produce healthy, fertile hybrids," Willis said.

Still, hybrids were not unheard of in cetaceans such as whales and dolphins-both in captivity and in the wild. Since cetaceans have very similar numbers of chromosomes across species, researchers had speculated they could produce viable hybrids more easily than other mammals.

"Ironically, one translation of clymene can mean notorious or infamous, and now this dolphin turns out it's living up to its name by being the first marine mammal known to arise through hybrid speciation," said study co-author Howard Rosenbaum, a marine biologist at the Wildlife Conservation Society and American Museum of Natural History in New York.

Future research will analyze the DNA of these dolphins in greater detail to help deduce how long ago the clymene dolphin arose, Amaral says.

This study "adds to an ever-increasing amount of recent research that indicates that hybridization is a common and important part of animal evolution, facilitating the formation of new species," Willis said.

"Traditionally, biologists have viewed hybridization as rare and either insignificant, evolution-wise, or serving only to meld species together into one," she said. "We're undergoing a paradigm shift in recognizing the creative role hybridization plays in contributing to animal evolution and diversity."

"Dolphins could help us better understand this rare form of speciation," added Rosenbaum. "We hope this work highlights the importance of conserving dolphins."

Follow Charles Q. Choi on Twitter and Google+.

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DNA Discovery Reveals Surprising Dolphin Origins

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A well-known dolphin species, the clymene dolphin, arose from mating between two separate and distinct dolphin species, report genetics researchers. Also known as the "short-snouted spinner dolphin," the clymene dolphin (Stenella clymene) grows to nearly seven feet (2.1 meters) long and dwells in deep waters in tropical and temperate parts of the Atlantic Ocean.

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North Atlantic Right Whales were hunted due to being presented as valuable resources for humans.

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Endangered Ocean: North Atlantic Right Whales

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A research topic about Indo-Pacific Bottlenose Dolphins' usage of echolocation.