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From Aotearoa Lakes.

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Life Cycle of a_ Kākahi - NZ Freshwater Mussel (final edit)

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From Aotearoa Lakes.

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New Zealand freshwater mussel.

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All the basics on importance, types, and biology of kākahi.

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What does science tell us about New Zealand freshwater mussels?

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Farah Hancock is a Newsroom reporter who covers environment, biodiversity and science.

environment

Michele Melchior's time spent wading through Waikato streams with her head in a "road cone" has led to a discovery about the reproductive tricks of one of New Zealand's least known creatures.

The University of Waikato PhD student is studying kākahi, New Zealand's freshwater mussels. The "road cone" is an underwater viewer with a glass lens, which Melchior uses to help find the mussels.

Historically an important food source for Māori and featuring in at least one New Zealand cookbook recipe, freshwater mussels are now harder to find, and off the menu.

Although many people have never heard of them, Melchior says they play an important role in the aquatic ecosystem.

"We have these really slow-growing, old-aged, filter-feeding bivalves in our streams. Because they are filter-feeding they can purify waterways."

Like mini underwater Roomba the mussels eat algae in the water and also take out pollutants and toxins. A single mussel can filter about one litre of water an hour. The toxins though can accumulate in the tissue of the mussel, making them unsafe to eat.

Even if a clean stream can be found with toxin-free mussels, it's advised you don't eat them. Globally, freshwater mussels are one of the most threatened freshwater organisms, with 70 percent of species, including New Zealand's, considered at risk, or threatened.

Melchior said both species she works with are in peril including the "super rare" Echyridella aucklandica, which is listed as threatened and nationally vulnerable and Echyridella menziesii which is listed as at risk and declining.

Echyridella aucklandica (top two mussels) and Echyridella menziesii (bottom two mussels). Photo: Supplied

Despite poor water quality in many Waikato waterways Melchior has been finding mature mussels during her hours in the field. Home for them is in sheltered areas of streams, rivers, and lakes.

"They are usually really camouflaged and are partially buried. It's most likely if you see them, you see these two little holes which are their syphons."

While they do seem to be able to filter out many types of pollution, one thing they struggle with is silt.

"They don't tolerate accumulated siltation or loose sediment from runoff or banks because the sediment clogs their gills and they end up dying off."

It's likely more than just sedimentation is driving the decline in numbers. The long-living bivalve can last for 50 years, and while plenty of mature specimens can be found there's a concerning lack of young mussels.

"That makes it much more special because this might mean that it needs a certain host fish."

Melchior's research, funded by the Ministry of Business, Innovation and Employment as part of NIWA's Cultural Keystone Species programme, has focused on their unique method of reproduction and how two different mussel species can co-exist, sharing the same resources. The discovery she's made may hold clues to the lack of juvenile Echyridella aucklandica mussels.

Unlike their saltwater counterparts, freshwater mussels need other species to act as an underwater baby carrier.

Saltwater mussels expel eggs and sperm and these get fertilised externally. They then float around until they settle themselves into a permanent home.

Freshwater mussels need to ensure their young are not washed out to sea. Eggs are fertilised inside female mussels where they are kept until they develop into larvae about 0.3mm long and are released by the mother.

The larvae are parasitic. Survival relies on finding a freshwater fish, latching on to them around the gills, head or fin and hitching a ride upstream until they are developed enough to drop from the host fish, into a home. Once there, they burrow around 10cm down and live hidden for around five years before they slowly make their way upwards.

For some species, the larvae is just attached to mucous strings which attach to passing fish by chance. This is the case of the more common New Zealand Echyridella menziesii which produce thousands of larvae.

Other freshwater mussel species try to trick fish into investigating their larvae.

Some North American mussels produce larvae "packages" which resemble fly larvae, as a way to attract host fish. Melchior has discovered the Echyridella aucklandica, the rarer of the two mussel species she studies, also use this type of trickery to entice host fish. This has not been seen outside of North American species before.

"They release these packages of their little baby larvae which look like leeches," said Melchior.

"That makes it much more special because this might mean that it needs a certain host fish, it's not a host generalist possibly. It might mean it needs one host fish and if that host fish isn't available anymore, it could mean the Echyridella aucklandica could be in a pretty awful situation."

Known host fish for the more common species of freshwater mussel include kōaro, giant bully and the common bully. Melchior has been searching for what fish carry the larvae of the Echyridella aucklandica.

"We do electrofishing, where you look at native fresh species and try to find a little larvae on the fish. We haven't found them yet, so we don't know. That's the next step."

Michele Melchior inspects the mussels to see if they are male or female and if larvae are present. Photo: Supplied

A recent report has shown 74 percent of New Zealand's native freshwater fish are threatened or at risk, meaning there's a chance host fish for the Echyridella aucklandica are in a situation as precarious as the mussels. Threats to native fish include the illegal blocking of waterways and pollution.

In other countries work is being done to increase freshwater mussel numbers. In Delaware in the United States, $11.5 million has been spent to set up a freshwater mussel hatchery. It's hoped by introducing mussels back into waterways in greater numbers water quality will improve. The hatchery hopes to produce a million baby mussels a year.

In New Zealand NIWA, has also been trying to breed the mussels. It has produced thousands of juveniles in vitro in petri dishes, but most died when they reached two months old. NIWA suspects two months represents a developmental milestone where the gut and gills are possibly formed. It hopes to find ways around this in the future so the mussels can be used to restock waterways.

Melchior, who will spend much of her summer with her underwater viewer, said a key part of conserving the bivalves is understanding their basic reproductive needs.

Once the needs are known, conservation measures can be put in place.

"Freshwater mussels are a taonga species, so they're pretty important culturally but they also filter our waters. They can take out impurities, like bacteria and toxins from our waterways."

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The reproductive trickery of NZ's freshwater mussels

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Farah Hancock is a Newsroom reporter who covers environment, biodiversity and science. environment Michele Melchior's time spent wading through Waikato streams with her head in a "road cone" has led to a discovery about the reproductive tricks of one of New Zealand's least known creatures.

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Near Maori Lakes inland from Ashburton, Lavinia Reihana-Moemate talks about collecting and preparing kuta or freshwater mussels. They were another important food for Māori who used to trek over to the West Coast for pounamu. Maori cooked the mussels by steaming them as they are toxic when raw. Lavinia gives meaning to the place name Ō Tū Wharekai. I wonder how you would go needing to hunt and gather all your food!
From the LEARNZ Wetland Biodiversity virtual field trip.
More at http://www.learnz.org.nz/fieldtrips

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When we think of our native freshwater mussels, "go-getter" may not be the first term that comes to mind.

In what is thought to be a world first, a new study is showing that native New Zealand kākahi behave in different ways according to their personalities.

Some take more risks, others wait until the coast is clear. Some rush around exploring their environment (the term "rush" is relative), others are content to wait for life to come to them.

Freshwater ecologist Amber McEwan of Masterton has undertaken a lot of work with various native freshwater species.

READ MORE:
* How your personality affects your pay packet
* Rare Kākahi (fresh water mussels) released in Wellington
* Giant extinct burrowing bat discovered in South Island
* Four types of drunks: Which one are you?

As part of her PhD research at Victoria University with Professor Jeff Shima, McEwan discovered, almost by accident, that kākahi exhibit different behavioral traits.

She was doing an experiment with around 80 tagged individuals in a tank and started to recognise something interesting.

"I started to notice that certain individuals were acting the same. I did some repeated trials looking at different types of activity and found that, yes, they were indeed exhibiting signs of individual personalities."

Unlike marine mussels, kākahi can move freely with the use of their muscular foot.

She saw that some were more bold and explorative while others more timid.

McEwan formulated an experiment where she could measure their activity to define their behavioural characteristics.

By watching how much they moved, how often they would extend their foot out of their shells and how deeply they would burrow in the substrate, she could collect data.

Giving the behavioural types labels such as "go-getters" or "just-lie-theres", McEwan was able to show how these personality types shaped their behaviour.

"Some of them were bolder than others, some of them were more active than others, some of them were just shy and cautious," McEwan said.

"One of the behaviours I looked at was probing propensity. Probing is the first step of burrowing. Putting their foot out is risky because it means that something could bite that soft tissue, but delaying probing is also risky, because it means they will be exposed to predators for longer."

The test of a definable personality is "consistent differences in behaviour through time or context" and by this definition McEwan believes the kākahi is showing these patterns across individuals.

"Then we say, ding, there's a personality. The data is indicative of different personalities which would be a world first demonstration for a bivalve."

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World first study shows native mussels have personalities

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When we think of our native freshwater mussels, "go-getter" may not be the first term that comes to mind. In what is thought to be a world first, a new study is showing that native New Zealand kākahi behave in different ways according to their personalities.

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200 Kākahi mussels are being translocated from Parangarahu Lakes and Wairarapa Moana to a sanctuary. Zealandia Co-Ordinator Pascale Michel says the freshwater mussel species are nationally in decline. Kākahi is a freshwater mussel species that play an integral part in water quality.

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The Kakahi is New Zealand's freshwater mussel! They are threatened and in decline, but are a vital filtering organism for our freshwater lakes and rivers.

The video below, by Bob Brown of Landcare Research, shows juvenile kakahi that are between 3 and 4 weeks old. They are now beginning to develop their brown periostracum (protective protein covering) of the adults.

DOC's endangered species ambassador Nicola Toki tells us all about these remarkable native creatures.

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Recent stories from Afternoons with Jesse Mulligan

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The Kakahi is New Zealand's freshwater mussel! They are threatened and in decline, but are a vital filtering organism for our freshwater lakes and rivers. The video below, by Bob Brown of Landcare Research, shows juvenile kakahi that are between 3 and 4 weeks old.

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Overview

Kakahi are New Zealand's freshwater mussels, but the number of species present and the scientific names to be used for them has been uncertain. They have been known by many different specific names, and referred to multiple genera in several families and subfamilies.

A research programme led by Te Papa's Bruce Marshall, together with Mark Fenwick (Te Papa, later NIWA) and Peter Ritchie (Victoria University), confirmed that there are three species of kakahi, one of which was new to science and all of which belong to the genus Echyridella.

Echyridella menziesii (Gray, 1843) is the most common and widely distributed kakahi. Because of its variability and over-naming, it had been known by a chaos of no less than 72 scientific names (8 specific/subspecific names combined in 5 genera/subgenera).

Echyridella aucklandica (Gray, 1843) is also widely distributed and occurs with E. menziesii, though it is less common. Less variable than E. menziesii, it has nevertheless been known by at least 33 scientific names (4 specific/subspecific names combined in 2 genera/subgenera). Until the 2014 revision this species was almost completely misclassified and remains relatively little known to field ecologists. Although occurring widely in the North Island with an outlier in the southern South Island, E. aucklandica is evidently more endangered by agricultural and urban runoff than E. menziesii (and E. onekaka), especially in Northland.

Echyridella onekaka Marshall & Fenwick, 2006 is superficially similar to E. menziesii and had long been confused with it in collections. It was recognised during genetic sequencing of kakahi from throughout the country, and proved to be restricted to the north-western South Island, west of a line between Takaka and Cape Foulwind.

Kakahi are an important indicator of freshwater quality. They feed on food particles filtered from the water, naturally occur in dense aggregations, and contribute to the health of their environment. Regrettably they are susceptible to pollution, notably agricultural and urban runoff, and many populations have vanished or are in decline.

Kakahi belong to the family Hyriidae, a group that provides strong evidence of former land connection between New Zealand, South America and Australia.

Kakahi specimens in Te Papa's Collections Online.

More on kakahi from Te Papa's Collections Online.

References:
Marshall BA, Fenwick MC (2006) Unio zelebori Dunker in Dunker & Zelebor, 1866, a form of Cafferia caffra (Krauss, 1848) (Mollusca: Bivalvia: Unionidae). Molluscan Research 26: 19-22. Online abstract.

Fenwick MC, Marshall BA (2006) A new species of Echyridella from New Zealand, and recognition of Echyridella lucasi (Suter, 1905) (Mollusca: Bivalvia: Hyriidae). Molluscan Research 26: 69-76. Online abstract.

Marshall BA, Fenwick MC, Ritchie PA (2014) New Zealand Recent Hyriidae (Mollusca: Bivalvia: Unionida). Molluscan Research 34: 181-200. Online abstract.

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Kakahi are New Zealand's freshwater mussels, but the number of species present and the scientific names to be used for them has been uncertain. They have been known by many different specific names, and referred to multiple genera in several families and subfamilies.

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NIWA scientists have made an important breakthrough in the battle to save New Zealand's freshwater mussels.

Scientist Sue Clearwater said the species known as Kākahi were once a valuable food source for Māori.

They also play a crucial role in detecting the health of waterways, but all three species are in decline.

Dr Clearwater has been leading research into Kākahi for the last few years, and said a University of Waikato doctoral student had recently found a clue around how to help prevent it.

Michele Melchior has discovered that the species use different reproductive strategies and that one in particular, that can live for more than 50 years, is dying out faster than its counterparts

Her PhD is part of the research programme called Cultural Keystone Species funded by the Ministry of Business, Innovation and Employment.

Dr Clearwater said the discovery could potentially provide scientists with the tools to save the species.

"This particular species can live a really long time - up to 50 years or more, but if they're not reproducing enough young they're not replacing themselves so they slowly die out and become a geriatric population."

The NIWA research shows that Kākahi were thought to reproduce by releasing clouds of larvae into a waterway. The larvae attach themselves to passing fish and "hitchhike" upstream to a new habitat where they fall off, settle and grow. They transform from a larva into a juvenile mussel during this "parasitic hitchhiking" phase.

Anything obstructing the carrier fish, including pollution and sediment, spoils the chances of the population surviving, the research shows.

"If these mussels are luring in a fish that maybe can't swim very well - which is what we think is happening, then any barriers to that fish getting to the mussels may mean that's why they're dying out faster than the species that can still attract fish getting past these barriers," Dr Clearwater says.

One species of freshwater mussels is found throughout New Zealand, but the species upon which Ms Melchior has made the discovery is found mainly in the northern part of New Zealand.

She has found that this larger Echyridella aucklandica species, mostly found in the Waikato northwards release their larvae in ways similar to how fly-fishing lures attract certain fish species.

She said as far as they know, this is the first known freshwater mussel species outside of North America to use these lures that mimic fish food items, as a strategy to attract and attach to fish.

Dr Clearwater said Ms Melchior's discovery was a big leap forward.

"It provides us with another piece of the puzzle towards understanding the mussel lifecycle, and it points to what we need to do to conserve and restore the species."

Dr Clearwater admitted to developing a fondness for Kākahi, despite describing them as the "cabbage of the aquatic world" - okay to eat but probably not the most favoured of foods.

"There's something quite primal about collecting nice big mussels from a stream, just like collecting tua tua at the beach. Also the adults can be old and tough, but the juveniles are so sensitive. That's what makes them so fascinating."

Kākahi are often found tucked under banks, in shady pools and partly submerged in shady, soft-bottomed streams.

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Scientists make break-through in saving freshwater mussels

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NIWA scientists have made an important breakthrough in the battle to save New Zealand's freshwater mussels. Scientist Sue Clearwater said the species known as Kākahi were once a valuable food source for Māori. They also play a crucial role in detecting the health of waterways, but all three species are in decline.

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Kākahi may not be the most well known of our native species, but they are critical to the health of our waterways. In this story, wel meet Amber McEwan who is exploring both mātauranga Māori and western knowledge to help bring them back from the brink.

This is part of the series In Her Nature: New Zealand women changing the way we connect with the world around us, exploring New Zealand women scientists working at the intersection of people and nature. These stories are a feature for the International Day of Women and Girls in Science 2020.

Exploring and expanding our knowledge of kākahi

Amber McEwan is at home in the water. She's a freshwater ecologist studying kākahi, New Zealand's threatened freshwater mussels, in Wairarapa Moana/Lake Wairarapa.

Kākahi live in lakes and waterways across New Zealand but are increasingly at risk from pollution and habitat loss. Most of New Zealand's mussel populations are large adults, which means that juvenile kākahi are not surviving until adulthood. Amber is exploring the best ways to move kākahi to new locations as part of conservation efforts to help them survive and reproduce effectively.

"My PhD topic is translocation ecology of freshwater mussels, which is an umbrella term for lots of different pieces of work that I'm weaving together. Under the umbrella at the moment is looking at mātauranga Māori methods and looking at the best way to transport them for translocation."

Kākahi have been a traditional mahinga kai/food source for Māori, and Amber wanted to test whether there are differences between moving kākahi in traditional kete/flax baskets, in buckets or in a hybrid of the two (a kete inside a bucket).

Kākahi were gathered from three sites across the region, working with mana whenua Taranaki Whānui, Ngāti Kahungunu ki Wairarapa and Rangitāne o Wairarapa to create locally specific kete. Two hundred kākahi were then moved to Wellington's ZEALANDIA ecosanctuary, where they will contribute to a rich and healthy freshwater ecosystem.

"The science was measuring how quickly they were able to secure a position in the sediment and how quickly they could burrow after being transported using one of those methods. And essentially, the main finding was the ones that were immersed in water the whole time did better."

The importance of community connections

As much as she loves working with the kākahi themselves, Amber values the connections being made with mana whenua and the knowledge that is being developed across both. Working with mana whenua and local communities is critical to the success of Amber's research and her wider goals of protecting Wairarapa Moana. More people are taking part in Greater Wellington's annual monitoring, where volunteers count and measure kākahi in the lake, checking their health and making note of shell erosion and other health indicators. Amber is seeing the benefits of working closely with the community.

"Now, we're getting more locals who live here and are able to bring a different perspective, and hopefully have more ownership of it all. Sometimes all it takes is one outspoken, motivated person to make a big difference in these areas. And there's a few of those people down here. I think that at least in Lake Wairarapa that mana whenua are getting closer together, and the Western scientists and mana whenua are getting closer together on lake work."

Useful links

Acknowledgement

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Can mātauranga Māori help save New Zealand's freshwater mussels?

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Kākahi may not be the most well known of our native species, but they are critical to the health of our waterways. In this story, wel meet Amber McEwan who is exploring both mātauranga Māori and western knowledge to help bring them back from the brink.

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The narrative fresh water mussels, known to Maori as kakahi and to science as Hyridella menziesii (and several related species), are oval shellfish, typically between about 50 and 90 mm in length. They resemble a pipi in shape, though they possess a black horny covering-the periostracum-like a marine mussel.

Kakahi once formed extensive beds in New Zealand lakes and rivers, living shallowly buried in sand or mud, like pipi, rather than attached to rocks in the manner of most marine mussels. They were valued by Maori as food, especially around inland lakes. A decline in their numbers in recent decades has prompted speculation about the cause and how it can be mitigated.

Some years ago, National Institute of Water and Atmospheric Research scientist Mark James suggested that a lack of juveniles in mussel populations in Lake Taupo indicated that the population was not maintaining itself. Possible factors in the population decline, he suggested, included sediment type, food supply, water quality, water velocity, bed slope and the absence of sufficient numbers of fish hosts for the mussel's parasitic larva.

A decline in the numbers of a freshwater organism is often blamed on deterioration in water quality-partly because this is easy to see. Phytoplankton blooms caused by high nutrient levels create "green water," which is harmful to many aquatic species. But this may be too simplistic a line of reasoning. It is even possible that phytoplankton blooms are a symptom of kakahi decline, not a cause.

How can the relationship between cause and effect be turned on its head like this? Consider a North American example. In recent decades, a small exotic shellfish, the zebra mussel, has invaded lakes in North America, becoming a serious pest. However, the proliferation of the mussel is not entirely bad news: people can now see the bottoms of lakes hitherto obscured by water turbidity, the improvement in water clarity resulting from millions of zebra mussels filtering out phytoplankton.

Could a reverse phenomenon be occurring in some of New Zealand's lakes? Has the decline in kakahi resulted in less water being "bio-filtered," leading to an increase in phytoplankton and thus a deterioration in water quality?

The absence of historical data on the abundance of kakahi makes this hypothesis hard to test; in any case, a decline in mussel numbers is unlikely to affect water quality in a lake the depth of Taupo. Besides, the question remains: if loss of kakahi means more phytoplankton, what is causing the decline of kakahi in the first place?

Like all molluscs, kakahi have a larval stage. The kakahi larva, called a glochidium, is parasitic, and attaches itself to a fish before subsequently settling in sandy sediments on a lake-or riverbed. In this aspect of its life cycle, kakahi differ from marine mussels-but it is for a common-sense reason. Marine bivalves produce eggs that hatch into tiny, free-swimming larvae. These spend a period being dispersed around the coast in the plankton before settling down to a less mobile adulthood.

In a river, however, free-swimming larvae would inevitably be flushed out to sea. The kakahi glochidium gets around this problem by sitting on the bottom and attaching itself to a small fish nosing among the detritus for food. Attachment can be to the gills, fins, snout, roof of the mouth or lips. While it is attached, the glochidium probably draws nutrients from the fish, but being only 0.3 mm long it is unlikely to cause its host much harm.

During the few summer weeks it remains attached, the glochidium has a fair chance of being carried upstream by the fish. Indeed, fish transport is the only hope freshwater mussels have of establishing an existence upstream of their parents. It is therefore possible that a reduction in the number of fish has caused the decline in kakahi.

As with kakahi, so with New Zealand lake fish: little quantitative information on their historical abundance is available. However, the history of trout introductions into the country's lakes is well recorded, and may be pertinent.

Before European settlement, Maori netted koaro whitebait-Galaxias brevipinnis-by the hundredweight in Lake Taupo. Early European explorers were offered whitebait as food in Maori villages around the lake. Whitebait were also abundant in the Rotorua lakes, and were an important food for tribes in that area. Yet today it is hard to find a single shoal of koaro in Lake Taupo. What has happened?

In a word: trout. The introduction of brown and rainbow trout in the late 1800s caused a massive decline in koaro numbers. The voracious trout thrived, generating superb fisheries, though by the early 1900s their condition had deteriorated in parallel with their increasing abundance. Tonnes of trout were netted and removed from Lake Taupo to reduce numbers and enable those left to regain condition. Rotorua Maori opposed the introduction of trout into their lakes, fearing the impact on traditional food supplies.

The trout food that was so reduced in Lake Taupo, and about which Rotorua Maori were concerned, was primarily koaro. Eventually, common smelt-Retropinna retropinna-were introduced as a substitute. These flourished-for some reason they are able to endure prolonged trout predation-and are now the primary food source of Taupo trout.

What has all this to do with kakahi? In Lake Taupo and the Rotorua lakes, the host of the mussel's parasitic larva was originally the koaro, and perhaps also the common bully‑ Gobiomorphus cotidianus. Koaro swam near the lake bed, and were thus accessible to mussel larvae when they were liberated at breeding time.

Now that koaro have been largely replaced by smelt in Lake Taupo, the mussel population has suffered. How so? Why don't kakahi larvae attach themselves to other fish now common in their waters, such as smelt, common bullies or trout-or even the brown bullhead catfish, now common on sandy substrates in Lake Taupo?

There is no single answer to this question, but some observations can be made. First, "replacement" fish species in Lake Taupo may be less accessible to kakahi glochidia than koaro were. Smelt and trout are mid-and surface-water fish, while bullies seem most common in rocky shallows, where there are few kakahi. It would be interesting to see if catfish make a suitable host, but no research on this possibility has been conducted.

It may be, of course, that the host-parasite relationship between kakahi and native fish is not transferable to introduced species. Hosts and their parasites often co-evolve, so that only traditional host species are acceptable to parasites, and this may be the case with kakahi-another question for research.

If this line of thinking is correct, the decline of kakahi in Lake Taupo may indeed be the result of the reduction in koaro. Similar changes may have occurred in other lakes. If so, and if kakahi play a role in filtering phytoplankton from the water as zebra mussels do, deterioration in water quality may, at least in part, be a symptom of loss of kakahi rather than a cause.

Taking this hypothesis further, if kakahi decline is not caused by deterioration in water quality, efforts to "clean up" lakes to facilitate recovery of kakahi populations may well fail. It would, of course, be nice to have cleaner lakes, but the expectation that kakahi populations would then recover may not be fulfilled. Sadly, I doubt that kakahi will ever be abundant again unless their larvae find a new fish host.

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The narrative fresh water mussels, known to Maori as kakahi and to science as Hyridella menziesii (and several related species), are oval shellfish, typically between about 50 and 90 mm in length. They resemble a pipi in shape, though they possess a black horny covering-the periostracum-like a marine mussel.

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by Hannah Rainforth

Scientist Hannah Rainforth investigated kākahi in the Whanganui River to find whether the evidence supports claims by local kaumātua that kākahi have nearly disappeared.

Back to series
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by Hannah Rainforth Scientist Hannah Rainforth investigated kākahi in the Whanganui River to find whether the evidence supports claims by local kaumātua that kākahi have nearly disappeared. Back to series Return to top ^

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We don't normally think of shellfish when we think of streams, rivers and lakes in Wairarapa.

And even if we did, it would be unlikely to imagine them spending a few weeks cruising around attached to a fish, before settling into a silty bed, filtering sediment out of the passing water and living for up to 50 years.

Unlikely as that may be, that's exactly what kakahi, New Zealand's freshwater mussels, have been doing for thousands of years. Right here in Wairarapa too. The kakahi of Aotearoa are the most powerful filtering freshwater mussel in the world. Put a handful in a container of murky water and they can clean it in a few hours. But before we celebrate this humble hero, we need to consider, they have been dwindling fast for the past 50 years and their future is uncertain.

Freshwater scientist Hannah Rainforth says this appears to be a typical story for kakahi throughout most of New Zealand. Hannah was at the Greater Wellington office in Masterton in May talking to a meeting of about 40 freshwater enthusiasts about the decline of kakahi in her study site, the Whanganui River.

There are three species of kakahi in New Zealand and two of these are found in Wairarapa. They can live between 30 years and 50 years and grow to between 60 and 80 mm, although there are records of much larger specimens.

Hannah says kakahi are found in sheltered parts of rivers and streams where the bed is sandy or silty, and in lakes. They burrow into the sediment and are hugely efficient at filtering sediment out of the water. Hannah says, in the past, large beds of kakahi probably helped to maintain the clarity and quality of our waterways. However, that's when they were plentiful.

Rangitane kaumatua Jim Rimene was at the meeting and says kakahi were certainly plentiful when he was young. He remembers them in the Kopuaranga, Whangaehu and Taueru rivers and says they made good convenience food when you were out and about.

"Our people used to have feed of them when they were out scrub cutting or fencing. The old people knew the spots to go to. That was in the days before we had baked beans and spaghetti in cans."

There are still records of kakahi found in the Kopuaranga and Whangaehu and the lower reaches of the Ruamahanga River, although in much lower numbers than they once were. They appear to be more plentiful in Lake Wairarapa. Kakahi don't usually live in heavy gravel rivers, such as the Waiohine and Waingawa, as these rivers lack the stable and sheltered spots kakahi favour.

Why are kakahi in decline?

Some rivers, like the Whanganui, have been changed by hydro-electric projects, with lower water levels leaving many former kakahi beds high and dry.

There has also been a decline in water quality caused by more silt getting into rivers and high levels of nutrients from effluent and fertiliser getting into waterways. These may be limiting kakahi numbers, but not directly.

Hannah thinks the decline may be linked to the kakahi's strange method of reproduction and the decline of New Zealand's native fish species. Kakahi larvae attach themselves to a host fish as part of their development, a parasitic behaviour shared by many freshwater mussel species around the world.

The kakahi larvae only spend a few weeks attached to a fish, before dropping to the river, stream or lake-bed and settling into the sediment. The fish the kakahi most often uses as a host is the native kōaro, which is one of the five native fish conmonly called whitebait. Kōaro can grow up to 25 cm and live for up to six years. Sometimes other fish become hosts, but the kōaro is the most suitable.

Kōaro are fantastic climbers and can get up very steep streams, which would have helped move the parasitic kakahi larvae around our waterways.

There are far fewer kōaro around than there once was. They've suffered from the drop in water quality, been eaten by introduced fish such as trout and been scooped up by whitebaiters for decades.

So with far fewer koaro to attach to, a critical part of the kakahi life-cycle has been interrupted, and far fewer kakahi larvae mature.

Blending culture and science

As a freshwater scientist, one of Hannah's passions is to make her studies relevant to the people who use our rivers, streams and lakes.

"We can measure nutrient levels, but what does that mean to the animals in the stream or the people that live next to it?"

Hannah grew up on the banks of the Whanganui River and as part of her study she interviewed the kaumatua up and down the river to find out the locations of former gathering sites and how kakahi were harvested and used. Some of the old people on the river remembered gathering kakahi by the canoe-full. They were eaten fresh or threaded onto pieces of flax and dried and stored for winter.

Hannah used this cultural information as a "baseline" for past abundance and location of kakahi.

She then used scientific methods and a fair amount of drifting around with goggles and a snorkel to measure the amount of kakahi at the historic sites, and made comparisons. Many kakahi beds had disappeared altogether or were hugely depleted. Only one out of the 22 sites was plentiful enough for gathering.

Hannah says using a cultural "baseline" makes her study easier to understand for non-scientists, and in some cases is the only way to get historical information, particularly when there are no scientific records.

"We need to use both methods, Western and iwi, to the get the full picture."

Looking for kakahi in your creek

Hannah has developed an excellent knowledge of kakahi on the Whanganui River and says her methods were simple.

"Anyone can do this. Science doesn't have to be hard. I used a snorkel, goggles, bucket, callipers to measure ($13 from a hardware shop), pencil and paper."

She used a mix of searching with goggles and digging with her feet as you would for pipis.

Hannah says if you've seen kakahi before, or your parents or grandparents have told you where they used to see them, why don't you go out looking for them?

If you find any, call Alton Perrie at Greater Wellington's Masterton office 06 370 5645 or your local Department of Conservation office. Every piece of information helps freshwater scientists find out more about kakahi and understand their decline.

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We don't normally think of shellfish when we think of streams, rivers and lakes in Wairarapa. And even if we did, it would be unlikely to imagine them spending a few weeks cruising around attached to a fish, before settling into a silty bed, filtering sediment out of the passing water and living for up to 50 years.

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(Not directly related to kākahi)

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A traditional Maori method of catching koura (freshwater crayfish) using a 'tau koura', or fern bundle, has worked well in koura abundance monitoring trials.

The tau koura is a traditional method used by Te Arawa and Ngati Tuwharetoa to catch koura in Central North Island lakes. The technique involves placing bundles of bracken fern ( Pteridium esculentum) on the lakebed that koura then colonise.

New research carried out by independent consultants and NIWA at Lake Rotoiti shows that tau koura had significant advantages over conventional monitoring methods such as baited traps and dive surveys.

Problems with conventional koura sampling and monitoring methods

Conventional sampling methods - baited traps, scuba diving, and underwater video camera -were all found to have a number of disadvantages in a preliminary study of koura sampling methods in the Rotorua lakes.

Trapping

mainly attracted large koura

koura attracted to the traps only if natural food supplies limited.

Diving and underwater video cameras

also biased towards large koura

heavily dependent on water visibility.

Advantages of tau koura

Tau koura:

captured a large number of koura of a wide range of sizes, in both shallow and deep waters

male and female crayfish of all sizes colonised the fern bundles

can be used in murky waters and at any depth

does not require specialised knowledge or expensive equipment.

So tau koura appears to provide more representative data on population structures than alternatives. Tau koura could be especially useful for monitoring by iwi and community groups, and in difficult conditions.

Environments where any koura monitoring is difficult

The tau koura method cannot be effectively used in high-growing aquatic plant beds, or areas of large boulders or wood. The fern bundles become entangled and difficult to retrieve.

But using baited traps, diving, and underwater video camera surveys are all difficult in these types of environments.

Retrieving used tau koura (Chris Hickey)

Monitoring by local iwi and community groups

Te Arawa Lakes Trust consultant Ian Kusabs, who has worked with NIWA on this project, says there are large numbers of koura living in North Island lakes.

"Koura are an important traditional food source for Maori. Maori are reasserting their kaitiakitanga (sustainable protection of resources), and it is important that iwi can monitor the wellbeing of species such as koura.

"There is a lack of quantitative information on koura, which makes it hard for iwi and government agencies to manage the koura populations in the lakes. The main reason for this lack of information is the lack of suitable methods to sample populations. That is why we need a more appropriate method.

"The tau koura method is particularly suited for use by iwi, who have exclusive rights to harvest koura in the Rotorua and Taupo lakes, and community groups. It is inexpensive, does not require specialist expertise, and avoids safety issues associated with diving."

Further work is planned to investigate how quickly koura colonise the fern bundles and the effects of lake water quality and different sorts of lakebeds and plants on koura populations.

Contact: Ian Kusabs ( ian@kusabs.co.nz)
Full paper - New Zealand Journal of Freshwater and Marine Research 43 (3)

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Traditional Māori fern bundles a better way to catch koura

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A traditional Maori method of catching koura (freshwater crayfish) using a 'tau koura', or fern bundle, has worked well in koura abundance monitoring trials. The tau koura is a traditional method used by Te Arawa and Ngati Tuwharetoa to catch koura in Central North Island lakes.

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Explore tikanga related to mahinga kai.

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The Waikato-Tainui relationship with the river is closely bound with the Kīngitanga and the Pai Mārire faith that King Tāwhiao brought back from Taranaki. Tikanga is a series of rules that are passed down from tūpuna (ancestors) and give Waikato-Tainui (and others) a basis for respecting the river, its resources and the environment. The purpose of tikanga is to find balance with and to protect the natural world of which we are all part.

The Kīngitanga is significant to Waikato-Tainui practices regarding the river. For Waikato-Tainui, the marae on the river are the centres of Waikato-Tainui communities that support the Kīngitanga and its values. Their histories continue to link them to the river and the Kīngitanga. Many Waikato-Tainui marae carry the names of the Kīngitanga and continue to celebrate poukai - gatherings that Tāwhiao began in 1884 to symbolise the importance of the relationship between the Kīngitanga and the marae.

Waikato-Tainui children have been raised to respect the river as a tupuna. Children were taught not to play in the river where taniwha (guardians) were known to appear. If they saw a taniwha making its way upstream, children were told to get out and sit on the bank to pay it respect.

In a similar way, tikanga taught people that the river was not to be polluted.

"We were taught not to mistreat the River by putting rubbish in it. My grandmother used to liken putting rubbish in the River to having rubbish being put in your own mouth."
(Statement of Evidence of Iti Rawiri, prepared for Anchor Hearing in the Environment Court, Appeal RMA 662/97, April 1998)

Tikanga also determines how fishing was to be conducted. For example, the first catch of every season is returned to the river, even if the net is full.

"That's for them, the tūpuna: that's your koha (thanksgiving) to them."
(Iti Rawiri, Oral History, 8 December 1998 cited in Parsonson, 1998)

Fish were allowed to die with dignity, and so they are not cooked straight from the river. Eels are also given respect in that they are not speared or disturbed while they are feeding.

When fishing, the tikanga is to only take what was needed. Often kaumātua will still caution fishers to only take what is needed and to not be greedy with food.

For marae, their mana is closely linked to kai. Marae have their own speciality foods. For example, for Tūrangawaewae, it was tuna (eel), for Horahora, it was kaeo (freshwater pipi), and for Tauranganui, it was matamata (whitebait).

Other resources are also important. Meat from freshwater kōura (crayfish) was sometimes used to rub on the gums of babies to help with teething. When it was used for this purpose, it was not used for eating. Watercress is used for food, raupō (reeds) were used for building houses and kiekie and harakeke (flax) are used for weaving clothing and whāriki (mats). These could be gathered from along the banks of the rivers and streams or from islands in the river.

Over time, constant human contact and a disrespect of the river has led to the decline of the health and wellbeing of the river. This has had an effect on the ability of marae to provide for their manuwhiri, and in turn, it affects their mana.

Some hapū and whānau put rāhui (restrictions on use) over certain times of the year to help fish stocks to replenish. Other practices include whānau letting others know when they are fishing so that a particular area of the river is not overfished. In some areas, such as Waahi Stream, different whānau had their own places where they would set their hīnaki (traps) for tuna, and in the lower parts of the river, different whānau had their own bench to set their net for whitebait. Tikanga would set the expectation that whānau rights would not be interfered with.

Rāhui can also be used to respect a death that has happened in the river.

Tikanga relating to childbirth involved newborn babies being taken to the river and being washed. This created a link between the life force of the river and the child so that they were one.

The river is also acknowledged as having healing qualities.

"[H]e waiora, he wai manaaki i te tangata, he wai whakaora i te tangata.
(The River is life-giving, the River nurtures the people, the River heals those who are sick.)"
(John Haunui, Oral History, 7 December 1998 cited in Parsonson, 1998)

Many people today still speak of the healing properties of the river. Many people from along the river have their own stories and experiences about the healing qualities of the river.

Acknowledgement

Copyright: Waikato-Tainui Endowed Colleges Trust.

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The Waikato-Tainui relationship with the river is closely bound with the Kīngitanga and the Pai Mārire faith that King Tāwhiao brought back from Taranaki. Tikanga is a series of rules that are passed down from tūpuna (ancestors) and give Waikato-Tainui (and others) a basis for respecting the river, its resources and the environment.

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Studies of native and introduced freshwater fish have shown that fish are highly resistant to 1080, even when exposed in field trials to very high concentrations of 1080 in water and food. Read the facts here.

Do 1080 baits in water harm fish?

No. Studies on multiple fish and aquatic species show that fish in water where 1080 is present are not affected.

NIWA monitored 16 sites across 4 streams before and after 1080 baits were added to the water at 10x the possible quantity that might fall into a stream during a 1080 drop. Three species of native fish, longfin eels, koaro, and upland bullies were monitored following the addition of 1080 to the water. The evidence: No fish died or suffered adverse effects. [1]

In a Landcare study, no 1080 residue was detected in the flesh of longfin eels exposed to 1080 cereal baits, and 1080 dissolved in water.[2]

A NIWA study of the effects of exposing koura (native crayfish) to 1080 baits showed that koura did not absorb 1080 from the water.[3]

In another study fingerling trout subjected to water with 1080 concentrations of 500 and 1000mg per litre showed no visible effect.[4]

In a US study fingerling bream and bass survived indefinitely in water containing 370mg of 1080 per litre, with no sign of any toxicity.[5]

What happens when fish eat 1080 bait?

Some fish do not eat 1080 baits whereas others do. In several studies fish have been force-fed 1080 to study its effects. In those studies no fish died or showed visible adverse effects, although some temporarily absorbed 1080 in very low concentrations.

In the Landcare study, The evidence: no 1080 bait was eaten by any of the longfin eels exposed to 1080 baits in water.[6]

In the NIWA study on koura, it showed that they did eat some 1080 bait. If they ate bait soon after it was dropped into the water, there would be traces of 1080 in their gut and tail muscles, though this had no visible adverse effects on them.[7]

Fingerling and adult trout force-fed with cereal pellets containing 4 to 8mg of 1080 also showed no visible effect.[8]

In a study for DOC, which analysed the uptake and elimination of 1080 in trout that were force-fed high doses of 1080 gel, no trout died or showed ill effects, although trout flesh had taken up low levels of 1080 . DOC referred the results to the Ministry for Primary Industries (MPI) to assess food safety.[9]

What happens if fish eat an animal that has eaten 1080 bait?

In the Landcare study, longfin eels were also fed possum meat that contained 1080 residue. None died or suffered adverse effects, although low concentrations of 1080 were found in the flesh of some eels shortly after they had eaten the poisoned possum gut meat.[10]

Is there a risk to humans from eating fish with 1080 residues?

If you catch and eat fish from areas where there has been a 1080 operation, the risk of 1080 poisoning is extremely low.

The evidence: MPI found that the peak 1080 levels temporarily reached within the force-fed trout, fall well short of breaching internationally accepted standards for human health.[11]

The concentrations of 1080 found in eels are so low that to risk death a 60kg person would need to catch and eat 5.5 tonnes of eel that had eaten 1080 contaminated possum.[12]

The concentrations found in koura would require an 85kg adult to eat 2,840 small or 720 large koura tails to risk death.[13] Given that koura are nocturnal, and noting that 1080 leaches rapidly from baits in water, the baits would need to be dropped very close to koura shortly before nightfall . This is highly unlikely in a 1080 operation, further reducing any potential risk.[14]

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Studies of native and introduced freshwater fish have shown that fish are highly resistant to 1080, even when exposed in field trials to very high concentrations of 1080 in water and food. Read the facts here. Do 1080 baits in water harm fish? No.

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This article will raise questions over value - at what point does Western Science value indigenous knowledge?

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When it supports their claims, Western scientists value what Traditional Knowledge has to offer. If not, they dismiss it

smithsonianmag.com

Our knowledge of what animals do when humans aren't around has steadily increased over the last 50 years. For example, we know now that animals use tools in their daily lives. Chimps use twigs to fish for termites; sea otters break open shellfish on rocks they selected; octopi carry coconut shell halves to later use as shelters. But the latest discovery has taken this assessment to new heights-literally.

A team of researchers led by Mark Bonta and Robert Gosford in northern Australia has documented kites and falcons, colloquially termed "firehawks," intentionally carrying burning sticks to spread fire. While it has long been known that birds will take advantage of natural fires that cause insects, rodents and reptiles to flee and thus increase feeding opportunities, that they would intercede to spread fire to unburned locales is astounding.

It's thus no surprise that this study has attracted great attention as it adds intentionality and planning to the repertoire of non-human use of tools. Previous accounts of avian use of fire have been dismissed or at least viewed with some skepticism.

But while new to Western science, the behaviors of the nighthawks have long been known to the Alawa, MalakMalak, Jawoyn and other Indigenous peoples of northern Australia whose ancestors occupied their lands for tens of thousands of years. Unlike most scientific studies, Bonta and Gosford's team foregrounded their research in traditional Indigenous ecological knowledge. They also note that local awareness of the behavior of the firehawks is ingrained within some of their ceremonial practices, beliefs and creation accounts.

The worldwide attention given to the firehawks article provides an opportunity to explore the double standard that exists concerning the acceptance of Traditional Knowledge by practitioners of Western science.

Traditional Knowledge ranges from medicinal properties of plants and insights into the value of biological diversity to caribou migration patterns and the effects of intentional burning of the landscape to manage particular resources. Today, it's become a highly valued source of information for archaeologists, ecologists, biologists, ethnobotanists, climatologists and others. For example, some climatology studies have incorporated Qaujimajatuqangit (Inuit traditional knowledge) to explain changes in sea ice conditions observed over many generations.

Yet despite the wide acknowledgement of their demonstrated value, many scientists continue to have had an uneasy alliance with Traditional Knowledge and Indigenous oral histories.

On the one hand, these types of knowledge are valued when they support or supplements archaeological, or other scientific evidence. But when the situation is reversed-when Traditional Knowledge is seen to challenge scientific "truths -then its utility is questioned or dismissed as myth. Science is promoted as objective, quantifiable, and the foundation for "real" knowledge creation or evaluation while Traditional Knowledge may be seen as anecdotal, imprecise and unfamiliar in form.
Ways of Knowing
Are Indigenous and Western systems of knowledge categorically antithetical? Or do they offer multiple points of entry into knowledge of the world, past and present?

There are many cases where science and history are catching up with what Indigenous peoples have long known.

For instance, in the past two decades, archaeologists and environmental scientists working in coastal British Columbia have come to recognize evidence of mariculture-the intentional management of marine resources-that pre-dates European settlement. Over the course of thousands of years, the ancestors of the Kwakwaka'wakw and other Indigenous groups there created and maintained what have become known as "clam gardens"-rock-walled, terrace-like constructions that provide ideal habit for butter clams and other edible shellfish.

To the Kwakwaka'wakw, these were known as loxiwey, according to Clan Chief Adam Dick (Kwaxsistalla) who has shared this term and his knowledge of the practice with researchers. As marine ecologist Amy Groesbeck and colleagues have demonstrated, these structures increase shellfish productivity and resource security significantly. This resource management strategy reflects a sophisticated body of ecological understanding and practice that predates modern management systems by millennia.

These published research studies now prove that Indigenous communities knew about mariculture for generations-but Western scientists never asked them about it before. Once tangible remains were detected, it was clear mariculture management was in use for thousands of years. There is a move underway by various Indigenous communities in the region to restore and recreate clam gardens and put them back into use.

A second example demonstrates how Indigenous oral histories correct inaccurate or incomplete historical accounts. There are significant differences between Lakota and Cheyenne accounts of what transpired at the Battle of Greasy Grass (Little Big Horn) in 1876, and the historical accounts that appeared soon after the battle by white commentators.

The Lakota and Cheyenne can be considered more objective than white accounts of the battle that are tainted by Eurocentric bias. The ledger drawings of Red Horse, a Minneconjou Sioux participant in the battle, record precise details such as trooper's uniforms, the location of wounds on horses, and the distribution of Indian and white casualties.

In 1984, a fire at the battleground revealed military artifacts and human remains that prompted archaeological excavations. What this work revealed was a new, more accurate history of the battle that validated many elements of the Native American oral histories and accompanying pictographs and drawings of the events. However, without the archaeological evidence, many historians gave limited credence to the accounts obtained from the participating Native American warriors.
Opportunities at the Intersection
Hypotheses incorporating traditional knowledge-based information can lead the way toward unanticipated insights. The travels of Glooscap, a major figure in Abenaki oral history and worldview, are found throughout the Mi'kmaw homeland of the Maritime provinces of eastern Canada. As a Transformer, Glooscap created many landscape features. Anthropologist Trudy Sable (Saint Mary's University) has noted a significant degree of correlation between places named in Mi'kmaw legends and oral histories and recorded archaeological sites.

As ways of knowing, Western and Indigenous Knowledge share several important and fundamental attributes. Both are constantly verified through repetition and verification, inference and prediction, empirical observations and recognition of pattern events.

While some actions leave no physical evidence (e.g. clam cultivation), and some experiments can't be replicated (e.g. cold fusion), in the case of Indigenous knowledge, the absence of "empirical evidence" can be damning in terms of wider acceptance.

Some types of Indigenous knowledge, however, simply fall outside the realm of prior Western understanding. In contrast to Western knowledge, which tends to be text-based, reductionist, hierarchical and dependent on categorization (putting things into categories), Indigenous science does not strive for a universal set of explanations but is particularistic in orientation and often contextual. This can be a boon to Western science: hypotheses incorporating traditional knowledge-based information can lead the way toward unanticipated insights.

There are partnerships developing worldwide with Indigenous knowledge holders and Western scientists working together. This includes Traditional Ecological Knowledge informing government policies on resource management in some instances. But it is nonetheless problematic when their knowledge, which has been dismissed for so long by so many, becomes a valuable data set or used selectively by academics and others.

To return to the firehawks example, one way to look at this is that the scientists confirmed what the Indigenous peoples have long known about the birds' use of fire. Or we can say that the Western scientists finally caught up with Traditional Knowledge after several thousand years.
George Nicholas, Professor of Archaeology, Simon Fraser University

This article was originally published on The Conversation.

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When Scientists "Discover" What Indigenous People Have Known For Centuries

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smithsonianmag.com Our knowledge of what animals do when humans aren't around has steadily increased over the last 50 years. For example, we know now that animals use tools in their daily lives. Chimps use twigs to fish for termites; sea otters break open shellfish on rocks they selected; octopi carry coconut shell halves to later use as shelters.

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2019 was another busy and rewarding year for Te Wai Māori Trust. As we head into 2020, we thought we'd share our highlights from this year: Developing our policy responses with Iwi and hapū input [...]

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Welcome to Te Wai Māori the Māori Freshwater Fisheries Trust Te Wai Māori was established under the Maori Fisheries Act 2004 to advance Māori interests in freshwater fisheries. We are a part of the Māori Fisheries Settlement and it's our role to advance Māori interests in freshwater fisheries.

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Read the article and watch the video (below), then challenge students to create the best filter for dirty water. Provide a range of materials, and see what they come up with! You can also link this to the way that soils filter our water before it ends up in our waterways.

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This is an example of filter feeding in marine mussels.

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Mussels are filter feeders. They draw in seawater and filter out phytoplankton and sediments, cleaning the water as they go.

This 25-second video is a before and after display of murky seawater, demonstrating the ability of mussels to help clear it.

The video was produced by Revive Our Gulf, the flagship organisation for the Mussel Reef Restoration Trust.

Note that the video does not have a soundtrack.

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Mussels are filter feeders. They draw in seawater and filter out phytoplankton and sediments, cleaning the water as they go. This 25-second video is a before and after display of murky seawater, demonstrating the ability of mussels to help clear it. The video was produced by Revive Our Gulf, the flagship organisation for the Mussel Reef Restoration Trust.

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Beautiful mini-doco on kākahi in the Wairarapa

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Beautiful mini-doco on kākahi in the Wairarapa

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Murky waters call for filter feeding friends, and that's where kākahi excel - working tirelessly to reduce algae and sediment in our lakes, rivers and wetlands. The health of a kākahi population helps to gauge ecosystem health, but their population is in decline and faces extinction if juveniles are not replenished.

Join community volunteers in their hunt for juvenile kākahi in Lake Wairarapa as part of a longitudinal citizen science study led by freshwater ecologist, Amber McEwan, and supported by Greater Wellington biodiversity advisor, Micheline Evans.

DURATION: 8 min

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Kākahi - LAKE STORIES AOTEAROA NEW ZEALAND

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Murky waters call for filter feeding friends, and that's where kākahi excel - working tirelessly to reduce algae and sediment in our lakes, rivers and wetlands. The health of a kākahi population helps to gauge ecosystem health, but their population is in decline and faces extinction if juveniles are not replenished.