Wednesday, April 1, 2009

Reproduction - Fascinating Fishes

After reading Chapter 9 and reviewing in-class notes, you should be able to answer this question for your assigned 'fascinating fish'.

This essay question should be answered here by April 8. This question tests your ability to apply the various concepts to a novel species or groups of species.

Describe the following reproductive traits and strategies for your fascinating fish and explain how these strategies are adaptive for the environment in which these fish live.

Breeding Opportunities
Mating System
Gender System
Secondary Sex characteristics
Spawning Site Prep
Place of Fertilization
Parental Care
Reproductive Guild
Timing of Breeding

Click on comment below and post your answer in essay form (600 words max). Do not cut and past text from a web site!

The illustrations on this post show an intriguing behavior of some planktivorous cichlid species, referred to as "lekking" after the Swedish word that means "to play" Some leks are done without the 'volcano-shaped sand dome' depicted here. For more on Cichlidae, click here.


  1. Species of the Family Pomatomidae are schooling fish that mate in the spring time as they migrate north from there warmer southern wintering waters to northern summer time grounds. These fish are non-guarders and pelagophils. Spawning takes place in the open ocean, the floating eggs are fertilized externally, and are left as they migrate to develop into larvae, which feed on plankton and eventually migrate toward the coast. Sexual maturity is believed to be reached sometime around age two. Bluefish are dioecius fishes, with no sexual dimorphism between the sexes, there is not external way of telling the difference between the two.

  2. Gobisoma, or gobies, are a fascinating group of fish with very interesting life history strategies. They are found in waters of various salinities all over the world. It is very difficult to generalize on their characteristics, since these are so variable for the different sub-groups.
    Studies have revealed that most gobies (e.g. Gobiodon sp.) normally start life as females, and are sequential, bi-directional protogynous hermaphrodites. When paired up, one (normally the larger one) changes sex to male to form a breeding pair. In the case of two males, the smaller changes sex to become female. Tigrigobius multifasciatus, another goby, is a functional hermaphrodite. A few Gobies are also functionally gonochoric (i.e., constant-sexed), but exhibit transient hermaphroditic ovarian structure among immatures. Hence, secondary sexual characteristics are rare in gobies.
    Generally, spawning occurs several times in the year. Some gobies (e.g., two-spotted goby) exhibit unusually flexible sex roles. That is to say, mating competition (and hence sexual selection) is very intense between males for mating opportunities with females early in the mating season, and vice versa. During the summer breeding months, male two-spotted gobies take up nests in empty shells, in rocky crevices or on algae. These nests are prepared and protected by these males. For example, a male will dig a hole under a mussel shell, and then hide it from competitors by piling sand onto it. Males will then vigorously court females. Production of sound, fin displays, momentary body darkening and territory disputes during courtship is common in gobies. Mating speed has been found to be correlated to body length, so that bigger males mate sooner.
    Gobisoma are demersal spawning species in which both breeding males (mostly) and females care for the eggs. Hence, they are guarders. Eggs are attached to a substrate, such as vegetation, coral, or a rock surface. They can lay anything from five to a few hundred eggs, depending on species. Ripe females have been observed to be multiple spawners, showing asynchronous ovaries, with oocytes at different stages of development. Males however can spawn every day, if given the chance. After fertilising the eggs (externally), the male remains to guard them from predators and keep them free from detritus. These fish use their pectoral fins to fan water over the eggs, creating a current of fresh, oxygenated water needed for them to mature.
    Later in the season, as males become increasingly scarce, and those that still are around often have their nests close to full with embryos. During this time, females court males intensely, as males with empty or partially full nests are hard to find. Interestingly, females at this time will resort to behaviors similar to what males employ at the beginning of the season. This change in mating competition from acting strongest on males early in the season to acting strongest on females late in the season is termed sex-role reversal.
    Another interesting phenomenon common in non-monogamous gobies is that only the top male and top female mate. Hence, all the other females have to wait their turn in a queue based on their size. This is due to the fact that females always out-number males in each group. Each fish has a size difference of about 5 percent from the one above and the one below it in the queue. If the difference in size deviates beyond this, a challenge will occur as the junior fish tries to jump the mating queue and the superior one responds by trying to drive it out of the group.
    Most gobies are important food items for commercially important fish like cod, haddock, sea bass, and flatfish, due to their small sizes. Hence, with high adult mortality, iteroparity seems most appropriate. Also, rapid hermaphroditism is advantageous in that a breeding pair can quickly be formed and reproduction carried on in the likely event of the death of half an existing breeding pair.

  3. Reproduction in the flying fish (family Exocoetidae) is rather unremarkable compared to their ability to glide out of the water. All of the approximately 70 species inhabit warm tropical and subtropical surface waters of the open ocean, and their reproductive behavior is closely associated to their habitat preference. The males and females show no secondary sexual characteristics and the lifespan of is generally around 2 years with sexual maturity at age 1. At multiple times during the spawning season, males and females congregate in spawning groups in open water near the surface. Studies addressing the timing of the breeding are rather sparse, but one paper suggests that movement of the Intertropical Convergence Zone, which affects temperatures and other important climatic factors of their environment, could be a cue for reproduction. In accordance with the lack of morphological distinctiveness and spawning behavior, there appears to be no mate selectivity by either sex. The eggs are relatively large compared to the size of the fish (about 1 – 2 mm) and pelagic, with long, adhesive filaments that enable them to attach to the floating vegetation. Following Balon, the reproductive classification of flying fish is 1.A.1 or nonguarding, broadcase spawning pelagophils. One might argue that they are phytophils because the adults spawn near and the eggs attach to floating vegetation, but this is only a facultative relationship.

  4. Fish of the family Scorpaenidae are bearers. After internal fertilization, the young grow in the female, however they receive all of their energy from yolk (Ovoviviparous) as opposed to a placenta (such as in lamnoid sharks).

    Sperm can be stored for later fertilization if need be. Once the young are born (around winter or spring), it will take anywhere from 5 to 20 years for them to mature, with the average life expectancy for most rockfish at over 50 years (quillback rockfish can live up to 95 years). Reproductive capacity of the female increasing with size and age, with the average brood size of half a million young (obviously most die). Despite this, rockfish have a fairly low reproductive rate and are very sensitive to exploitation.

  5. Since the Pegasidae have little economic value as well as having only 5 species there is not a large amount of information available on them as a whole Genus but some information of each species can be found. The Pegasidae tend to have low numbers, so opportunities to mate may be low. Some species when they do mate though mate repetitively. Additionally the red sea seamoth (Eurypegasus draconis) is monogamous and spawn repetitively at dusk. Others within this Genus were not specified as to having this trait or not. The red sea seamoth also has dimorphic genders. Females have larger carapace volume compared to males. This genus has no site preparation. They release eggs into open water/substrate where the eggs are then fertilized. Since they release their eggs in open water to be moved about by the ocean currents they do not have parental care and do not guard their eggs. With this information the reproductive guild that the Pegasidae would be put into is the pelagophil cattegory. Time of breeding was hard to specify the only real data found was that the red sea seamoths show a clear seasonal peek in breeding every year. Overall these traits for reproduction could deal with the area they occur in. Since they occur in tropic waters with large species diversity it may be hard to find a mate so they pair up to ensure breeding. Additionally with so many fish being present in their habitat and the fish being rather small they may need their energy for other things such as predator avoidance and upkeep rather than being able to put the energy into nest building, guarding or other forms of parental care.

  6. Dasyatidae, or stingrays, invest a great deal of energy into producing a few young rather than thousands of offspring. The average female stingray will produce five to thirteen offspring, and since there are so few produced, more energy is put into each offspring which ensures a higher survival rate. Stingrays only have one litter per year, and breed in the winter. Dasyatidae are first ovoviviparous, but the egg has insufficient nutrients and the yolk is quickly consumed by the embryo. They then become aplacental uterine viviparous and receive most of their nutrients from histotroph, a milky substance secreted by the mother’s uterus. The embryo absorbs this through their skin. They are usually in the uterus for about two to four months. The females give birth to live young, and some are half as large as full grown adults and they have all the physical characteristics of adults. There appears to be no specific site where courtship or breeding occurs and no site is prepared. Fertilization happens internally and is achieved when one of the male’s claspers enters the female’s cloacae and deposits sperm. Females tend to be larger than males. During courting, males follow females closely and bite the female’s pectoral disc.

  7. Jessica wrote:
    The family Scombridae is composed of tunas, mackerels, and bonitos. They belong to the class Actinopterygii and the order Perciformes. There are 15 genera and 51 species in this family. They are found in brackish or marine waters, but not in freshwater. The reproductive strategies and characteristics of Scombridae fish are interesting to look at as they travel in schools and are often found out in the open ocean.
    Members of Scombridae are dioecious, meaning that the male and female sex organs are found in different individuals; no one individual has both male and female sex organs. Individuals show little or no sexual dimorphism in the form of patterns on their bodies. Typically, however, females reach larger sizes than the males. They also show little to no dichromatism. These differences are absent even during spawning.
    Scombridae fish fill the reproductive guild of non guarders. The members of this family are non guarding, open substrate, pelagic spawners so therefore do not have any spawning site prep work to do. Non guarder refers to the idea that once the eggs are laid/fertilized, the parental care of these fish is absent. They do not guard their eggs or young in any way, and for this reason the survival rate of eggs is low. Open substrate spawners fertilize their eggs externally in the open water. Since they breed in the open water, their eggs must be buoyant. This is usually achieved through an oil gland in the egg that provides buoyancy. The buoyancy of the eggs near the ocean surface also increases the likelihood that they will be eaten by predators. Typically, Scombridae members spawn in large groups or schools without elaborate courtship behavior and without specialized reproductive structures. Within open substrate spawners, they belong to the pelagic spawners group, meaning that they spawn in open waters near the surface. Scombridae fish are serial spawners. Serial spawners release several batches of eggs throughout the year, regardless of season. They do not have a specific breeding time in which they are able to reproduce; they can do it any time of the year. Given the high mortality rate of the eggs and young, it makes the most sense that adults are able to breed throughout the year in order to ensure a better chance that enough offspring will last to keep the species continuing in the future.
    Embryo development lasts 32 hours, and larval stages last about 30 days when temperatures are at or near 24°C. The eggs of this family are about 1mm in length and are pelagic. They hatch into planktonic larvae that are about 2.8mm in length at hatching.

    Breeding opportunities: serial spawners
    Mating system: promiscuous
    Gender system: dioecious
    Secondary sex characteristics: no dichromatism, size is only feature of dimorphism
    Spawning site prep: none; open substrate spawners
    Place of fertilization: external
    Parental care: non guarders
    Reproductive guild: non-guarders; open substrate spawning/pelagic spawners
    Time of breeding: serial spawners; release several batches of eggs throughout the year
    Ichthyology text book

  8. There is 12 species of lutjanidae, also know as snapper. Snapper do not spawn over a set period of time but is more dependent on things such as water temperature. These fish may spawn several times over the spring and summer periods. There peak spawning period is between the months of June to early September. During the winter month’s snapper move further offshore to avoid the cooler inshore waters. Female snapper release fertilized eggs into the water usually over flat sandy bottoms, which float close to the surface and hatch three to four days later. Once the eggs are released there is no parental care of the young and the new larvae are on there own from here. Some snapper may produce over 9 million eggs during a singles spawning event. After hatching juveniles hide and swim to a sandy/muddy bottom which provides an excellent source of food. The young feed on phytoplankton, zooplankton and marine worms and usually grow about four inches in there first six months. As the juveniles mature they seek cover in rocky structures, reefs, ledges and wrecks. Lutjanidae are believed to reach sexual maturity after 3 years at which point they are on average 12 inches long. Snapper are estimated to live between 40-50 years.

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  10. Uranoscopidae (Stargazers)are found in shallow, sandy bottom, tropical waters throughout around the world. They spawn on the bottom all year long with peaks during the summer months. Transparent eggs are fertilized externally and allowed to slowly float toward the surface. The parents take no park in insuring offspring survival (non-guarders). The larvae originally survive on their yoke sac till they are approximately 6-7mm in length or until it is completely consumed where they start to feed on other larvae in the water column. They continue to do this until until they are about 12-15mm where they start to take the shape of a juvenile stargazer. Also at this size, the electric organ starts to develop and the fish start to migrate to the bottom in shallow bays where they stay for several years. During this time the eyes will migrate to the top of the head. Once they have reached about a foot long, they will move offshore where they stay to live out the rest of their lives.

    Breeding system.
    Reproductive guild: nonguarders Open water/substratum egg scatterers
    Time of breeding: year round with peak during the summer months
    Breeding opportunities: serial spawners
    Mating system: promiscuous
    Gender system: dioecism
    Spawning site prep: none
    Place of fertilization: external
    Parental care: non guarders

  11. There are only three species that make up my fascinating fish group, genus Hypophthalmichthys, commonly known as the carp. Reproduction in the carp usually takes place in water that is around 25۫C. These fish are found in large rivers and also small rivers and streams. They are dioecious, meaning that the male and females produce separate gametes that need to join in order for reproduction to occur. These fish are open water egg scatterers. Fertilization is external; the females release eggs and the males release sperm. The sperm have to fertilize the eggs in the water.
    Neither of the parents protects the eggs and therefore they are not protected from predation, they are non-guarders. The carp can produce up to 400,000 eggs! They must have enough fertilized eggs in order for some of them to survive to hatching. Eggs hatch after about two days and during that time they get taken down the river by the current into deep open water.
    Spawning usually occurs during the warmer months of the year. It can happen starting in April until September before it gets too cold. Hypophthalmichthys usually reach maturity between three and six years, with the majority taking between four and five years. At this time, they can produce eggs and sperm to be fertilized. Female carp only release eggs once a year. They ascend to the top of the stream and release many thousand eggs. Only releasing eggs once a year pretty much forces here to release a lot. This gives her eggs the best chance to be fertilized by a male.
    You can distinguish between male and female carp by their size. Females are usually larger than males. They also have a larger belly then do the males.

  12. The walking catfish or Clairias batrachus begins it’s mating ritual in the late spring/ early summer where it participates in a mass spawning migration. Though the mass spawning migration is a constant amongst Clarias batrachus, the time of year may vary. These fish can be found around the world as naturally occurring species in South East Asia, India, Sri Lanka, Bangladesh, Burma, Indonesia, Singapore and Borneo. However, the walking catfish is renowned as one of the worlds top 10 worst introduced species, and can be found as an invasive species in the USA, Hong Kong, Taiwan, China, UK, Papua, New Guinea, Guam, Taiwan and Thailand as well. In many of the more tropical locations of Clarias batrachus, seasons are not something that are easily distinguishable in the tropical climate. In South-East Asia and other tropical climates, Clarias batrachus pursues the same mass spawning during the rainy season as opposed to late spring. During this time river levels are up and the fish can create nests in submerged mud banks in which to reproduce later. During these migrations, the catfish seek out ideal grounds for spawning. The favored environment appears to be inundated rice patty fields in the catfish native environment. These fields are ideal because of the swampy, wetlandish conditions which provide the catfish with comfort and food. Once an ideal ground is chosen, the fish lay their eggs in one of two ways. The eggs are adhesive and cluster together after leaving the female, however, they can be laid in a nest that has been made up just for this occasion, or amongst submerged vegetation. Both sites provide moderate protection for the eggs. The catfish lay the eggs in a hole which is dug to a diameter of about 12 inches. Both partners help in the digging process. The female lays the eggs and does not return to give the hole a second glance. Babies emerge between 30-40 hours after the eggs have been laid. The male stays with the young an additional 48 hours, and then they are left with neither parent for protection or help. This is a cruel introduction into the world.
    After the eggs are laid in the nest site, whether it be a prepared nest or simply a selected spot in the vegetation, the male is the parent who watches over them to protect them from predators. Once late summer arrives juveniles begin to appear. Sexual maturity is attained at the end of the first year. Unlike the Perciformes the walking catfish reach sexual maturity, develop into a male or female and the story ends there. There is no hermaphroditism in the species and mating is far from unusual.
    Though mating is not an unusual procedure for the walking catfish, it is still worth knowing about. Clarias batrachus exhibit very little sexual dimorphism. It is hardly as extreme as many other aquarium species. During mating season, the female and male develop only slightly differently. The female catfish, will have “button shaped” genital papilla, while the male genital papilla develop more lengthy, fingerlike genital papilla. Save for this minor difference there are very few differences in appearance between the 2 genders.
    The mating of the walking catfish is a somewhat private process. While many fish simply take a cluster approach to mix eggs and sperm, the catfish pair up. During the day long mating process, the catfish are a couple. Though the spawning migrations are en masse, the mating itself is a somewhat private matter. As stated, the female lays eggs and fertilization is internal.

    Gulf States Marine Fisheries Commission. Clarias batrachus (Linnaeus, 1758). 8/3/2005. 4/5/09.
    Scotcat. Clarias batrachus (Linnaeus, 1758). 8/2/2004. 4/5/2009.

  13. Funky Fish Diodontidae

    The order Diodontidae are the porcupine fish, known for their poisonous spines and abilities to puff up when frightened by filling with water or air. Not much is known about their mating activities. Once a year they have a seasonal spike in mating. Because they are nocturnal fish, they only breed at sunrise and sunset. One or more males will push the female up towards the surface, from where they hide in the coral reefs when they are ready to mate. They are pelagophils, or pelagic spawners, which means they mate in the open water, letting the current take the eggs out to sea. The eggs require external fertilization and the fish are dioecious. This means that the species do not have any hermaphrodites and both male and females possess sexual organs exclusive to their gender. Because after fertilization the parents give no care to the eggs, they are considered oviparous. There also appears to be no dimorphism and after maturation juveniles keep their colors and size for the rest of their life. The species appear to be monogamous or polygamous, which means that one or more males can mate with a single female at one time.
    After fertilization the porcupine fish do not come in contact with the eggs, therefore they are non-guarders. Once mating is finished the eggs drift into epipelagic zone carried by currents. The eggs have oil filled sacs, which make them buoyant, leaving them towards the surface, where there are fewer predators than at the bottom. After four or five days they hatch into fry, which seek shelter in bunches of seaweed called sargassum. Here they are susceptible to predation from dolphin, or mahi’ mahi’ or many types of billfish. Once the juveniles reach eight inches they shed the hard shell around their bodies and start to produce spines. Then they become mature enough to venture to the benthic coral reefs where their parents live. Here they eat crustaceans or coral which they break with their hard teeth. Porcupine fish are a very elusive species, which scientists do not know much about. Above are a list of the reproductive strategies of the porcupine fish.

  14. The family Carangidae consists of 140 species mainly recognized by the anglers by the name Jacks or Pompanos. Most fish in the Carangidae family are pelagic species except for a few species which live closer to shore in grassy estuaries. Despite extensive studies much of carangidae’s reproduction is still not fully clear. It is believed the majority of these species spawn in the spring, through the summer, and into the fall. These species show dioecism, meaning there are truly males and females involved in reproduction. Although many of the species show little if any dimorphism occasionally dichromatism can be seen in slight color changes. Before the spawning season the fishes do little to preparation besides get together at a spawning site. Using a mating system known as promiscuity the many fishes both male and female in sex deposit eggs or sperm into the pelagic open ocean for external fertilization. The eggs contain a drop of oil which makes them buoyant allowing the eggs to scatter over the ocean. Fishes in the family carangidae are non-guarders leaving the eggs to float until hatching and formation of fry. Since there is a low survival rate in the free-embryo and larval stages of those eggs the fish are iteroparous. If the fish is in comfortable latitude in preferable water temperature it may spawn at various times throughout the spawning season. Since there is a market demand on the meat from jacks, there is hope for more research to better understand the reproduction of these fishes.

  15. Pimelodidae is a family of catfish that are most commonly known as the long-whiskered catfish. They have 3 pairs of barbels, where the maxillary barbel can extend to the length of its body and currently occupy the South American region, especially in the Amazon Basin. Most of these fish are medium to large in size and acts as an important as well as a great sport fish to people that inhabit South America. Most retail aquariums carry a common species of Pimelodidae which includes the pictus catfish, Pimelodus pictus. There is very little known about the reproductive behavior of these fish because close to nothing has been reported on these fish, so for this reason I will focus on a few key species that have been studied. Unlike most catfish, Pimelodidae are nonguarders meaning that they do not guard their eggs. Brachyplatystoma rousseauxii is one of the most important species of catfish in the Amazon and suggests that this creature has the longest reproductive migration for any known freshwater species of fish. The catfish yellow-mandi, Pimelodus maculatus, is found in the Igarapava Reservoir. Being a migratory species, it needs shorter lotic stretches of river to spawn than other Neotropical migratory fish. This species departs from the Corumbá Reservoir for the Upper Paraná River basin for reproductive purposes. This process can last several months with a fecundity of around 3,200 eggs and a gonadosomatic index of around 5.5. The reproduction of Neotropical migratory fish happens during the rainy season. The larvae or eggs are small and buoyant and float passively to downstream floodplains where they begin their first stages of life. During research of the yellow-mandi there was a lack of juveniles caught indicating that recruitment in certain areas was very minimal.

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  17. Currently, there are three distinct species that are recognized within the family Molidae. Theses species include the common mola, Mola mola, the sharp tailed mola, Masterus lanceolatus, and the slender mola, Ranzania laevis. Throughout the world, a number of intriguing common names exist for this fish including Poisson Lune (France), Manbo (Japan), Toppled car fish (Taiwan), and the most common, the Ocean Sunfish. The Ocean sunfish is the heaviest known bony fish in the world, with an average adult weight of 1,000 kg. The species is native to tropical/temperate waters and is found on slopes adjacent to deeper water. The species is known to travel alone.
    Little to nothing is known about the reproductive methods of the Ocean Sunfish so some educated speculation is needed. Ocean sunfish reproduce sexually. The mode of reproduction in the Mola mola is dioecism. Dioecism is characterized by having the male and female reproductive organs borne on separate individuals of the same species. This leads for separate productions of two gametes to form a zygote. In terms of a reproductive guild, the Ocean Sunfish release their eggs into open ocean water, specifically the surface waters (pelagic). They scatter their eggs throughout the ocean in hopes of the sperm of a male to come into contact with it. This external fertilization is known as being an open substrate pelagic spawner. The eggs remain suspended in the water column due to their high water content/oil globules. Following releasing of their sperm/eggs, there is no more parental investment. This process is known as being a non guarder. Due to the small chance of fertilization and non guarding of progeny, low survival rate is seen. In order to adapt to this low survival rate, the Ocean Sunfish produces a very large number of eggs. A large female was once estimated to be carrying 300 million eggs in a single ovary. No other vertebrate in the world has ever come close to this number at any one time.
    In terms of spawning timing, the Ocean Sunfish is said to be a batch spawner. A batch spawner releases eggs/sperm at various times coinciding with the seasons. By timing their release, energy invested in reproduction is used more wisely. Due to low fertilization rate and high mortality rate after fertilization, it is energy efficient to release eggs/sperm during a more prolific time period. Proper water temperature, seasonal positioning, and water content (nutrients) aid in raising fertilization and lowering mortality rates.
    When looking at sexual dichromatism, little to nothing is known. However, Mola come in a multitude of colors, from a basic grey to a spotted darker color. Certain geographic locations have distinct color patterns. Mola are capable of color changes when being chased or stressed, thus it is possible that sexual dichromatism is seen. Sexual dimorphism is not seen with the Ocean Sunfish.

    Breeding Opportunities/Timing of Breeding: Situational/Batched
    Mating System: Dioecism
    Secondary Sex Characteristics: Female Size
    Spawning site prep: Nonexistent (open substrate)
    Fertilization: External
    Parental Care: Non Guarders
    Reproductive Guild: Non Gaurders, Open water/substratum egg scatterers

  18. The requiem sharks from the family carcharinidae share reproductive strategies amongst their multiple species. They are all live bearers with most being viviparous. Only the tiger shark is oviviparous, having its young develop inside the body using only nutrition from the egg they are in. Breeding typically occurs in the spring or summer months and gestation periods vary among individual species with the average being around a year. Since most species are solitary hunters, reproducing adults must know when and where to go to breed. Little is known about how sharks know when and where to mate but speculation may suggest that water temperature and photoperiod may indicate to adult sharks that it is time to mate. They may also return to the same spawning areas each year in order to find a mate as well.
    Females and males are usually not distinguishable without close observation but the method of courtship may sometimes prove them apart. During courtship, the male shark will swim along side of the female shark and align his body thus that his claspers are near the female’s cloaca. He will then insert his clasper into her cloaca and release his sperm into her. The clasper helps direct the sperm into the cloaca so that fertilization may occur. While this process if going on, the male shark usually holds onto the female shark by biting her. This can sometimes harm the female shark, and the resultant scarring can sometimes be used to sex the sharks. Also, in some species females have developed some resistance to this practice by having skin that is about three times thicker than the male’s skin.
    Parental care is slight if any since the baby sharks are born live and capable of swimming and feeding on their own. Most sharks abandon their young at birth and let them fend for themselves. Depending on the location of birth, this can be dangerous for the young. Pelagic birth requires the baby sharks to escape from any predators that may be around, including other sharks. Some species, like the bull shark reproduce in brackish water near river mouths which can provide more hiding places for newborn sharks until they grow larger.

  19. The Merlucciidae family is a marine fish of hakes, which are similar to the cod. They are in the Gadiformes order with four genera and eighteen species. They normally migrate from deeper to shallow waters as well as from northern to more southern. These fish usually have a high number of eggs released at one time. They are non-guarders and the eggs are usually in the pelagic zone of the ocean. They are dioecious and have no dichromatism. They have a small oil gland to help with buoyancy like the majority of fish. It is uncertain about the timing of when they breed but certain studies show that the reproduction occurs during spring and summer and a peak in January. I was not able to find when they were sexually mature.

  20. The Mudminnows, family Umbridae, are a rather small group of minnows, containing only seven specific species. From May to late June, the Mudminnows congregate in slow-moving water, usually overflow pools, to spawn. Males will court the females for hours, but will not display any color changes during the mating season. Once the female has found her mate, she will deposit approximately 2000 eggs onto nearby vegetation. The male will then deposit his sperm onto the eggs at which point they will begin to be fertilized. The female Mudminnow will remain with the eggs guarding and clutch tendering them until their hatch approximately 1 week after fertilization. She will vigorously guard the eggs from any approaching egg predator, which often times includes other Mudminnnows.

  21. The triggerfish, or family Balistidae, is a group in the order Tetradontiformes. Triggerfish are found around the world in the Atlantic, Pacific, and Indian Oceans. This group of fish has very distinct sexual characteristics that separate it from many other families. Most species of triggerfish are polygynous, meaning they mate with many others of the opposite sex as opposed to being monogamous. Another distinct characteristic about this family is sequential hermaphroditism, meaning one sex may transform into members of the opposite sex in order to increase the chance for reproduction. Although not widely documented, research shows that some species in this family exhibit this sexual characteristic. In addition, species of triggerfish exhibit sexual dimorphism between males and females involving color schematics, predominantly in males. In this process, males compete amongst each other using varying color schemes on lateral and dorsal sides in order to make themselves more appealing to females. Research has shown that in some species females exhibit sexual dimorphism as well. Traditionally, before a mate has been chosen, the male triggerfish makes large depressions in the sand for potential spawning sites once the female arrives. Once the female has chosen her mate, the mass of eggs is deposited in his spawn site and the male pushes larger bits of sand and rocks piled on top and around the mass to ensure it from disturbance or harm. In most species of Balistidae, the male takes parental watch and care over the eggs post-fertilization. Other research has shown that both male and female take biparental care of the eggs. Triggerfish are also guarders, using reproductive guilds to ensure reproductive success and survival of young.

  22. Catfish of the Pangasius genus are river spawners that reproduce once per year in the later summer or early fall depending on the species. Pangasius catfishes are diecious, staying either male or female for their entire lives. In some species the females cannot be distinguished from the males except for a possible wider girth. During spawning season the gender of some species, such as Pangasius sutchi, can be determined by a reddish tinge to their genital openings and a swollen distended belly in females. These catfish reach sexual maturity based on size, but a general age of sexual maturity is 4 years. Sexual maturity can be reached much sooner in captivity using pituitary hormone treatments.
    Pangasius catfishes will swim downstream to spawn in the tidal belt. They are open water substratum egg scatterers. Neither parent pays any attention to the eggs once they are fertilized, except as an occasional snack. Fertilization is accomplished externally. Overall, the Pangasius catfishes are not very different from other siluriformes in their reproductive habits.

  23. Gasterosteiformes are a diverse family that include the seahorses, pipefish, and sticklebacks. This order is dioecious, the males and females both produce gametes for fertilization. The breeding opportunities, or time that they breed depends on the fish. Three spine sticklebacks generally breed between late March and early August because there is plenty of food available for their young. Stickleback males are polygamous and try to attract as many females as possible to their nest (because it takes so much time!). Secondary sex characteristics for the three spined sticklebacks are that during spring the males undergo a transformation of color. Their throats and stomach turn bright red, their scales turn silver, and their eyes turn blue. The colors warn off predators and other males as well as attract females. Three spine stickleback males make their nests from plant material and a sticky substance they secrete from their kidneys. The nest is put together by the mouth of the male. The male then attracts females to the nest with his bright colors. Once a female is attracted to the nest, she lays her eggs in it and the male fertilizes them. Sticklebacks are “gluemaker plant-material nest guarders” and actually exerts a lot of parental care at this time, because the eggs need a lot of oxygen, so he flaps his fins in oxygen rich water and drags the water over them. The eggs then hatch and the male continues to look after the larvae for about a week or so.
    Seahorses and pipefish (Sygnathidae) are found in a variety of latitudes and therefore climates, so the family Sygnathidae are found to breed either throughout the year or they can also be seasonal depending on when food is available. The mating system for the Sygnathidae class is appears to be monogamous. Secondary sex characteristics for Sygnathidae are that the males carry a pouch which they sometimes inflate to attract females. Sometimes, the females have the pouch and therefore carry the eggs. So, Sygnathids are bearers-pouch brooders. The pouch is for carrying the eggs and larvae, like a marsupial. For Sygnathids, site preparation can be up to a week of practicing transfer of the eggs from female to male before the event actually takes place! Fertilization takes place inside the female and then the fertilized eggs are transferred to the male in a penis like ovipositor. The carrier of the eggs (either male or female) then carries the eggs until hatching and sometimes even into some of the larval stages.

    Moyle, P.B., Cech, J.J. (2004). Fishes, an introduction to ichthyology. Pearson Benjamin

  24. Parrotfish belong to the family Scaridae. They are considered to be protogynous. Parrotfish are generally born females but in the instance the dominant male in the group disappears, then usually the biggest and most aggressive female will change into a male. There is not really a need to have many males because one male can produce enough sperm to fertilize a larger number of females. Reproduction can take place in two ways: by group spawning or pair spawning. Group spawning is where there are many more excited males than females. Pair spawning is where the male performs an elaborate courtship display which includes a sexy dance and brushes along the female's side with his fin. Some smaller males have also been observed doing a behavior called streaking. Spawning usually occurs just before dusk and can occur repeatedly throughout their breeding season. The parrotfish life-span ranges from 5 to 20 years.