Advantages:

• Monogamous pairs often establish and defend a territory together, this ensures that the young are protected and have the proper resources as one parent can stay guard while the other one can forage for food.

• As they form a monogamous bond they don't have to spend energy and time competing for mates, allowing them to focus their resources on their offspring.

• Males are surer that the offsprings are theirs, making them have greater care and protection for their offsprings.

Disadvantages:

• Monogamous bonds can limit the genetic variation, this can make populations more vulnerable to disease and environmental changes

• If there is limited movement between populations, it can lead to inbreeding which will lead to deformities and reduced fitness.

• If one of the parent is lost the remaining parent may struggle to care for the offspring by themselves.

Examples:

• French angelfish, Australian Hippocampus whitei, sea otters (R12, R13)

Advantages:

• Since individuals mate with so many mates, it can be difficult to know whether a young individual is related to them so killing a juvenile is risky. This makes it so that more juveniles live.

• Offspring benefit from a more diverse genetic pool, which can enhance adaptability and resilience to environmental changes.

• With multiple male and females, parental duties can be shared, increasing the chance of offspring survival

Disadvantages:

• High risk of spread of sexually transmitted diseases.

• Despite multiple mating partners there can still be competition as some females may still aim for males with better genes, this can lead to injuries.

Examples:

• Dolphins, Two pipefish (Syngathus typhle, Nerophis ophidion) (R10,11)

^Advantages:

• ^{A single male can father many offspring, making sure that his genetics will continue to the next generation}

• ^{Females can choose high quality males desirable traits, which makes their offspring have better genetic quality}

• ^{Females can choose males that are successful this allows them to have access to better nesting sites, food and protection}

^{Disadvantages:}

• ^{It is very easy for sexually transmitted disease to spread in polygyny systems.}

• ^{If only a few males dominate the mating pool, it can reduce the genetic diversity of the population, making it less adaptable to disease.}

• ^{As the males want to be dominant, it often leads to competition among males, which can lead to physical injuries or even death}

^Examples:

• ^{Southern elephant seals, Bluehead wrasse, sea lions (R8)}

Parental care:

They exhibit parental care for their calves through nursing which can last for 18 to 24 months. Mother dolphins share a close bond with their calves and provide guidance for their calves. They also help to ensure the calves safety and development.

Dolphins Plus (n.d.) 'How dolphins mate', Dolphins Plus. Available at: https://www.dolphinsplus.com/blog/how-dolphins-mate (Accessed: 29 July 2024).

Euronews (2022) 'Dolphins derive pleasure from very complicated vaginas, new research finds', Euronews. Available at: https://www.euronews.com/green/2022/05/07/dolphins-derive-pleasure-from-very-complicated-vaginas-new-research-finds (Accessed: 29 July 2024).

ResearchGate (n.d.) 'Mounting behavior between adult male bottlenose dolphins', ResearchGate. Available at: https://www.researchgate.net/figure/Mounting-behavior-between-adult-male-bottlenose-dolphins_fig2_285512444#:~:text=Bottlenose%20dolphins%20(%20Tursiops%20spp.),sexes%20mate%20with%20multiple%20partners (Accessed: 29 July 2024).

Surf's Up Magazine (n.d.) 'Baby dolphins', Surf's Up Magazine. Available at: https://surfsupmagazine.com/baby-dolphins/ (Accessed: 29 July 2024).

Study.com (n.d.) 'Dolphin mating & reproduction', Study.com. Available at: https://study.com/academy/lesson/dolphin-mating-reproduction.html#:~:text=It%20has%20been%20noted%20by,they%20are%20ready%20to%20mate (Accessed: 29 July 2024).

Study.com (n.d.) 'Dolphin mating & reproduction', Study.com. Available at: https://study.com/academy/lesson/dolphin-mating-reproduction.html#:~:text=Dolphins%20are%20polygamous%2C%20meaning%20they,the%20mother%20for%20five%20years (Accessed: 29 July 2024).

Whale Scientists (n.d.) 'Dolphin males' pair bonds', Whale Scientists. Available at: https://whalescientists.com/dolphin-males-pair-bonds/#:~:text=Having%20a%20friend%20that%20acts,which%20can%20appeal%20to%20females (Accessed: 29 July 2024).

Young dolphins will remain with their mother for a few more years after the period of breastfeeding has been completed. On average is about 3 to 6 years in total. During this time, the young dolphin learns everything they can about social relationships, hunting methods, finding food and anything else they may need to be an adult dolphin.

High parental investments in dolphins which provides better care, leading to higher survival rates and healthier offspring.

High adaptability in dolphins as they can adjust their reproductive efforts based on environmental cues. For example, they can delay reproduction during unfavorable conditions and wait for better circumstances.

Since the young is developing inside the embryo, they are less dependent on external factors (such as temperature or humidity) for successful reproduction. This can create a stable internal environment for embryo development.

Characteristics

• Undergo significant physiological changes to support their single reproductive effort, such as increased energy storage and alterations in metabolism.(R3)

Advantages

• Semalparous species produce more offspring in their single fatal reproductive episode (R2)

• Allocates all their available resources to maximize reproduction during their single reproductive episode, often at the expense of their future survival (R2)

• Often referred to as 'big bang' reproduction due to its significant reproductive output in one event (R2)

Disadvantage

• Death of a species after the first reproduction process. (R2)

• They are particularly vulnerable to environmental changes and disruptions, as their reproductive success hinges on a single event (R3)

• Often evolve in environments where the probability of surviving to another reproductive event is low. (R3)

Examples

• Pacific salmon, some mollusks, including octopus and squid etc. (R3)

  
  

By having separate sexes, individuals avoid competing with each other for resources needed for reproduction.

ezlyn- purple

kai yuan- green

bryan- red

josh- blue

alesha (dolphins)- blue

Disadvantages are that there are fewer offspring per production cycle and that there is strong sexual selection at individual level

Advantages

• Iteroparous species typically invest resources into multiple reproductive events over their lifespan. This allows them to spread their reproductive effort across different periods, often leading to more stable population dynamics. (R4)

• Repeated reproduction can increase the chances of offspring survival by spreading the risk of reproductive failure over multiple events (R1)

• Iteroparous organisms often invest more in the development and care of their offspring (R1)

• Beneficial in stable environments where adult survival is high as it allows for multiple reproductive events and potentially better overall population growth. (R1)

• Often produce fewer offspring per reproductive cycle but the offspring are generally larger and more developed at birth (R2)

Disadvantages

• May invest less in each reproductive episode compared to semelparous species. (R1)

• Often balance between reproducing multiple times and investing in growth and survival (R1)

Examples

• vertebrates: all birds, most reptiles, virtually all mammals and most fish, sea turtle, great white shark, manatee, seahorse (R2 & R5)

Advantages

• Number of total spawners directly influences the number of eggs produced and consequently, the potential recruitment of new individuals into the population (R6)

• Some fish species form large spawning groups, making it easier to estimate total spawners but also making them more vulnerable to overfishing (R6)

• High number of total spawners generally indicates a healthier population with better chances of maintaining or increasing its size (R6)

• Monitoring total spawners is crucial for setting sustainable fishing limits and managing fish populations. Ensuring that adequate numbers of spawners are preserved helps maintain population size and stability (R6)

Disadvantages

• Number of spawners vary significantly with seasonal changes, environmental conditions and habitat quality. Example, changes in water temperature, food availability or habitat conditions. (R6)

• Low spawner number may signal potential issues in reproductive success or population health (R6)

Examples

• Clownfish, yellowfin tuna, atlantic cod, herring, grouper, mackerel etc. (R7)

Advantage:

• Almost all males will be able to mate, allowing them to pass their genes to future generations, which does not occur in polygyny as only the most dominant males' mate.

• By mating with multiple males, the female will have offspring from a larger genetic base, which may enhance the survival and adaptability of her young.

Disadvantages:

• Mating with multiple partners has the increased risk of sexually transmitted disease to be passed to the female and her offspring.

• Mating with multiple males is time and energy intensive, making it maybe to neglect the existing offspring

Examples:

• Anglerfish, sea dragon, sea horses, pipefish (R9)

Advantages are that the developing young are protected within the mother body, so survival rate is higher and that they are less exposed to predation compared to eggs laid in environment. They have greater certainty of fertilization, lower production of gametes required and less risk of gametes desiccation.

Disadvantages are that the young require a significant energy investment from the mother to nourish the developing young and they can also pose as risks to the mother and may limit her ability to escape from predators as the mother have to protect her young. Fewer offspring per production cycle and strong sexual selection at individual level.

Advantages

• By spawning in batches, fish mitigate the risk of complete reproductive failure due to environmental fluctuations or predation

• Often have prolonged reproductive period, allowing them to take advantage of varying environmental conditions for egg and larval survival

Ecological Constraints

• They need habitats can support extended reproductive activities such as consistent food supply and suitable conditions for multiple spawning events

• Stable environments are more favorable as they reduce the risk of adverse conditions affecting multiple spawning events

Evolutionary adaptations

• May develop physiological adaptations that allows them to produce and release eggs over an extended period. (such as energy storage mechanisms)

• May exhibit behaviours that enhance the survival of multiple batches, such as choosing optimal spawning times and locations repeatedly throughout the season

Management implications

• Understanding batch spawning behaviour is crucial for setting fishing regulations that protects spawning fish throughout their reproductive period.

Example

• Atlantic Cod, pacific herring, groupers

Advantages are that the eggs are protected within the mother body which reduces the risk of predation, embryos develop in a controlled environment ensuring better survival rates for the offspring. Greater certainty of fertilization, lower production of gametes required and less risk of gametes desiccation.

Disadvantages are that the mother must provide all the resources for the developing embryos which can be taxing.

Carrying the developing young can also make the mother more vulnerable to predators.

Advantages are high reproductive rate where they produce a large number of eggs which can increase chance of offspring survival. Parents do not need to invest energy in caring for the eggs or offspring allowing them to conserve energy for other actions. Higher genetic diversity due to large mixing of genes within a group.

Disadvantages are high mortality rate as they are left unprotected so predators and environmental factors can lead to them dying. Uncertainty of fertilization and wastage of gametes

Female sea turtles migrate long distances to lay eggs on specific beaches where they carefully select and prepare nest sites by digging holes in the sand where their eggs will be laid.

Advantages:

• Gonochorism reduces the likelihood of inbreeding and the associated negative consequences, such as reduced genetic diversity and mutation.

• Males and females can develop specialized structures to optimize their reproductive roles. Males can develop specialized structure that can help to attract females, while females can develop structures that support fertilization or parental care.

Disadvantages

• An imbalance in the sex ratio can lead to reduced reproductivity, as it may be hard for the individuals of the more abundant sec to find a mate

• If the population size of the species is too small it may make it vulnerable to extinction due to the need of the presence of both males and females for reproduction. If one of the sex becomes to rare the population may be at risk

Examples:

• Bluefin Tuna, dolphins, orcas, seals, Atlantic cod, salmon (R14)

Advantages:

• As individuals have both male and female reproductive organs, an individual that they meet is a possible mate. This maximizes the chances of reproduction.

• In cases where there are no available mates, they are able to self-fertilize. This makes sure that they can still reproduce even in isolation.

Disadvantages

• However, self-fertilization has its negatives as inbreeding can lead to reduced genetic diversity and mutations

• Maintaining both reproductive organs requires significant energy and resources. This may deviate the individuals growth, survival and overall fitness

Example:

• Indigo hamlet are reef fish that engage in a behavior called egg trading, where two individuals take turns to fertilize each others eggs during a single mating season. (R15, R16)

Sexual size dimorphism where one sex is typically larger than the other and that this is common in many taxa including fish where often the females are larger. For example, clownfish and anglerfish. There are also male species that are bigger than female species. For example, cichlid fish and angelfish. (R21)

Advantage:

• In species where size is an advantage for the males, the individual can start of as a female to reproduce early when they are smaller an as they get bigger and more capable of fighting for mates they can transition into a male.

• It also allows for the individual to be flexible as if a population is female dominant then they can transition into males to balance the sex ratio

Disadvantages

• The transitioning phase requires significant energy an they will be vulnerable while in the transition phase.

• If the population of males decrease due to predation or environmental changes, there might be a temporary shortage of males until the females transition, this may decrease reproductive success momentarily.

Example: Indo pacific cleaner wrasse where the largest female will court the other fish and develop male organs within two weeks (R17, R18)

Advantages:

• In the early stages the male can focus on producing sperm which is less energy intensive, than producing eggs but once the individual grows larger and accumulates more resources they can invest in more energy into egg production

• Larger females also can produce more eggs. This means that there is more offspring which gives it a higher chance for the genes to continue

Disadvantages

• Changing sex from male to female requires extensive amounts of energy. They are also vulnerable when in the transition phase

Example:

• Clownfish, there are usually two large fish, one male and one female, which are sexually mature with many other smaller fish. All the smaller fish are male. If the female is removed the large male will take over her place and become female and the next largest fish in the group will rapidly increase in size and take over the role of the sexually mature male. (R17,R20)

Advantages:

• As the individuals are able to switch sex at anytime, this allows any two individuals to breed without venturing out in search of compatible mates

Disadvantages:

• It takes a lot of energy for the individual to switch from male to female or female to male.

• The physiological mechanisms required to switch reproductive roles or maintain the ability to perform both roles can be complex. This complexity can affect reproductive efficiency.

Example:

• Coral dwelling gobies, experience limited mating opportunities and a high risk of mating between spatially isolated coral colonies. The ability to change sex repeatedly in either direction allows any 2 fish to form a heterosexual breeding pair, thus reducing travelling distance and predation risk when finding a partner as well as time between breeding events (R18, R19)

Advantages:

• As the eggs float around, and are released in large numbers, they can be dispersed over a large distance.

• Produces large amounts of eggs.

• Well-developed larvae at hatching, higher survival rates.

Disadvantages:

• Adults do not provide parental care.

• Eggs exposed to many threats, (e.g. currents, predators etc.)

Example: Tuna, Halibut, Sardines

Advantages:

• Eggs can be hidden within the substrate, avoid predation.

• Some substrate spawners guard their eggs, increasing survival rates.

• High number of eggs, increase survival rates.

• Large area of where the eggs spread.

  
  

Disadvantages:

• Increased predation risk due to high egg volume and spread of the eggs.

• Needs suitable substrate on spawn on, reproduction rates may decrease if suitable substrates are not present.

  
  

Example: Rainbow cichlids attach their eggs to various surfaces, such as a leaf, a vertical piece of slate, or even aquarium glass.

Advantages:

• Decreased predation, predators are unable to find the eggs to consume.

• Limited parental care, lesser energy is spent on caring for the eggs and more on hunting, eating etc.

• 
  

Disadvantages:

• Some parental care is present, not always protected by parent fishes, so they can be vulnerable to predators, increasing their mortality rates.

• Lesser eggs, survival chances lower.

Example: Bitterling females deposits their eggs between the gill filaments of mussels. The male then spawns his sperm into the mussel’s inhalant water current and fertilization takes place within the gills of the host.

Advantages:

• As the brood is being guarded, parents can actively deter or fend off predators, this increases the likelihood of the offsprings survival

• Some species fan their eggs to ensure that they receive enough oxygen, which is crucial for their development.

Disadvantages

• Guarding the brood requires significant energy, which can detract from other activities like foraging or avoiding predators. It is also very time consuming to constantly protect the brood which could mean less time for activities such as foraging for food

• As they are protecting their nests the parents are more vulnerable to predation

Example:

Rock dwelling cichlids which typically guard their broods in the rocky areas and crevices of Lake Malawi. Both parents participate in guarding their fry, however the female usually takes a more active role (R23, R24)

Advantages:

• Nests can be hidden or defended by one or both of the parents, this provides a safer environment for the offspring.

• There is also increased parental care, as the parent will guard and fanning the eggs for oxygen this increases the survival of the offspring.

Disadvantages:

• Building and the defending of the nest requires significant energy, it is also very time consuming to build the nest and guarding which can limit the time for feeding

• Nests can also be destroyed by environmental events such as floods, storms or human activities

Example:

Beta fish use bubble nets, which is a series of bubbles that the betta fish forms at the water surface. Males are the primary builders of the bubble nets, using them to prove to a mate that they are capable of caring their young. The male usually moves the eggs to the nest and protects them until the baby betta fish swim off to live independently. (R22)

Advantages:

• High parental investment of the eggs, more protection and higher survival rates.

Disadvantages:

• A lot of energy is spent on caring of eggs, instead of hunting etc.

• Lesser eggs, smaller population

Example: Sharks, brotulids, and seahorses

2. Dr. Samanthi. (17 December 2019). Difference Between Semelparity and Iteroparity, Retrieved from Difference Between Semelparity and Iteroparity | Compare the Difference Between Similar Terms

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8.The Editors of Encyclopedia Britannica. (2014). Polygyny | marriage. In Encyclopædia Britannica. https://www.britannica.com/topic/polygyny-marriage

‌9.polyandry in fish. (n.d.). Bing. Retrieved July 30, 2024, from https://www.bing.com/search?q=polyandry+in+fish&qs=n&form=QBRE&sp=-1&ghc=1&lq=0&pq=polyandry+in+fish&sc=10-17&sk=&cvid=7192AA6213F4408C8A26FE3ABE655BC3&ghsh=0&ghacc=0&ghpl=

10.Furniss, K., & Hammarlund, S. (n.d.). 10.5 Promiscuity (and Polygynandry). Open.lib.umn.edu. https://open.lib.umn.edu/evosex/chapter/10-5-promiscuity-and-polygynandry/

‌11.Szala, A., & Shackelford, T. K. (2019). Polygynandry. Encyclopedia of Animal Cognition and Behavior, 1–2. https://doi.org/10.1007/978-3-319-47829-6_1904-1

‌12.Whiteman, E. A., & Côté, I. M. (2004). Monogamy in marine fishes. Biological Reviews, 79(2), 351–375. https://doi.org/10.1017/s1464793103006304

‌13. Walum, H., & Young, L. J. (2018). The neural mechanisms and circuitry of the pair bond. Nature Reviews Neuroscience, 19(11), 643–654. https://doi.org/10.1038/s41583-018-0072-6

‌14.Gonochorism - an overview | ScienceDirect Topics. (n.d.). Www.sciencedirect.com. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/gonochorism

‌15.Simultaneous Hermaphroditism - an overview | ScienceDirect Topics. (n.d.). Www.sciencedirect.com. https://www.sciencedirect.com/topics/immunology-and-microbiology/simultaneous-hermaphroditism

‌16.Libretexts. (2022b, August 24). 2.13: Indigo Hamlet. Biology LibreTexts. https://bio.libretexts.org/Bookshelves/Marine_Biology_and_Marine_Ecology/A_Student's_Guide_to_Tropical_Marine_Biology/02%3A_Common_Fish_in_the_Coral_Reef/02.13%3A_Indigo_Hamlet

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26.https://earthlife.net/fish-reproduction-guide-to-spawning-brooding/

‌

Advantages:

• Parent fish provides they young with food for their growth, and the young does not have to hunt for food themselves, increasing their survival rates.

• Growth of fish young will also be faster.

• 
  

Disadvantages:

• Energy consuming, parent fish have to hunt and search for food for the fish young, which cost a lot of energy.

• Repeated back and forth to the location of the fish young by the fish parents may lure predators that may consume the fish young.

Example: Tropheus duboisi, a mouth-brooding African cichlid, when ingesting food, part or all of the food taken by female parents are ingested by their young held in their buccal cavity.

Schooling is one of the primary ways many fishes help defend themselves and their young from predators. About 80 percent of all fish species school as juveniles and roughly 20 percent school as adults. Many ichthyologists say that the concept of “safety in numbers” plays a fundamental role in schooling behavior.

Mouthbrooding is a parental strategy that involves some species of fish keeping their eggs or newly hatched fry. This is to protect the eggs and young from predation, by keeping them close, secure and protected from the outside surroundings.

Many fishes also protect their eggs and young by guarding. An example is how male sunfish chase off fish that come too close to their eggs, no matter their size.