How do fish reproduce?

We explain how do fish reproduce an oviparous, viviparous and ovoviviparous and other manner. In addition, what are reproductive migrations with breeding period and season. so lets read that How do fish reproduce?

How do fish reproduce?

Fish are marine , abundant and diverse vertebrate animals in the different oceans , lakes and rivers of our planet . Many of them are part of the diet of humanity, while others may become companion animals.

These are species of eukaryotic animals. They breathe through gills and are equipped with fins instead of legs , distributed differently throughout their bodies.

Fish are only a fraction of the aquatic animals that exist, that is, they are immersed in complicated dynamics of predation and competition . Therefore, the reproduction of fish is not an ecologically simple matter.

In reproduction, courtship strategies are common to attract the female , such as dances, nest fabrications, etc. In addition, different species developed diverse methods to guarantee the perpetuity of the species .

The reproduction is almost always sexual , since fish, as the great common of animals are born with a certain (female-male) sex. In general, it occurs in three different ways: oviparous, viviparous and ovoviviparous. We will see each of them below.

Types of fish reproduction

reproduction of betta fish
Betta fish have a ritual mating complex.

As we said before, fish reproduce in three different ways, depending on the specific species we are talking about. These modes are:

  • Oviparous reproduction . As the name implies, it is about reproduction by eggs, which is most common in the species of fish that exist. This usually occurs through external fertilization strategies, that is, the female lays her eggs in the environment and then the male fertilizes them with her sperm. There are also rare cases in which eggs are fertilized within the female through intercourse.
  • Viviparous reproduction . This type of reproduction, similar to that of human beings, implies the internal fertilization of the female, the maturation of the breeding in its interior thanks toplacental nutrition and then its expulsion through a birth canal, ready to start Yourindependent life . Only about 53 families (around 900 species) of fish have this type of reproduction, which has the evolutionary advantage of ensuring that the offspring leave the world as mature as possible.
  • Ovoviviparous reproduction . This is a method of reproduction that combines the previous two in a certain way: the female lays eggs inside, which are fertilized internally by the male during intercourse. Juvenile specimens grow inside these eggs, without the need for maternal placentas, until they are ready to hatch the eggs. Only then does the female deposit them in the environment, or even expel them into the water around her moments before or after birth.

Hermaphroditism of the fish

reproduction of the hermaphrodite flame angel fish
The flaming angelfish is one of the few hermaphrodite species.

In the vast majority of cases, fish have separate and well defined sexes. However, there are species in which hermaphroditism is common , that is, they have both sexes or alternate between them in some state of their sexual maturation.

Some species, for example, grow like females and at some point in their adult life they “change sex” (proteroginic species), so to speak, or vice versa (proterrandic species). In contrast, simultaneous hermaphroditism, in which an individual has both functional sexes at the same time, is extremely rare in vertebrate animals.

Did you know that hermaphrodite fish exist?

Explaining how fish reproduce in the case of hermaphrodites is an interesting and enjoyable process, since hermaphrodites do not have a specific sex and can become female or male at will depending on the need for mating. This is known as simultaneous hermaphroditism.

However, there is another type of hermaphroditism in which fish are male for the first part of their life, and then become female . This is called protandric hermaphroditism, while the opposite (first female and then male) is called protogenic hermaphroditism.

Fish breeding migrations

reproduction of fish migracion salmon
During their breeding migration, salmon swim through rivers against the current.

Migratory species are those that make long trips or trips with the sole purpose of reproduction or spawning . Some even alternate between fresh and salt water in this movement, which they would not normally do in their daily lives.

The classic example is salmon , a sea fish that once reached sexual maturation, traces the rivers upstream to reach its usual places of spawning. This difficult displacement is done by jumping upstream, an opportunity that many of its predators on land take advantage of to seize their prey.

Fish territorialism

For the nesting species it is essential to defend the territory. Some species show a very pronounced territorialism, like many angelfish. Adult males defend their territory and do not allow entry to any other males. For this reason, it is common for juvenile angelfish to have another livery, that is, a different coloration. In this way the territorial males allow other young males to be in their same territory. By the time these youngsters reach sexual maturity and adopt adult coloration, they will have to find a new territory where they can attract females and have offspring .
Typical coloration of juveniles of various species of angelfish.

Change color

There are species that present different liveries throughout their development , such as the student ( Chromis chromis ), which in the juvenile stage shows an electric blue color and when they are adults they adopt a dark coloration. The trumpeter ( Macroramphosus scolopax ) lives in coastal areas between 50 and 150 meters, its color is reddish, a color that serves as a camouflage in depth. The young, however, are pelagic and to be able to camouflage themselves on the high seas, they wear a blue color with a silver belly.
Some fish, such as julia ( Coris julis ), green fish ( Thalassoma pavo), as well as many wrasses, have sexual dichromatism. Males and females are externally distinguished as they display different colored liveries. Males usually wear more striking colors to attract females.

How do fish reproduce in the aquarium?

If we want to increase the family in our aquarium we must take into account the following considerations:

  • Obviously, we must be clear about how the fish in our aquarium reproduce.
  • It is important to know that some fish will present sexual dimorphism , that is, males and females have different colors or sizes, which helps to differentiate them.
  • Other fish will be hermaphroditic , they can behave as males or females indistinctly, they can reach sexual maturity as females and become males or vice versa.
  • Depending on the reproductive characteristics of our fish, this is how we must arrange the space. For example, if they are fish that spawn on rocks, they should have them at their disposal.
  • You have to count on that in some cases the newborn fry will have to be separated , as their parents or the other fish could eat them.
  • Likewise, it is important that we reproduce the ideal conditions of their habitat. The temperature, pH, cleaning and oxygenation of the water or food must be suitable.
  • Having a group of fish promotes successful breeding.
  • The feeding must be sufficient. Be careful with overfeeding, as it could make us think that a female is pregnant. We will also have to take special care of the feeding of the fry.
  • We must pay close attention to our aquarium since some females may have come to us fertilized, as is the case with guppies.

Finally, in this section we will explain how the fish best known to children reproduce, the clown fish popularized by Nemo. As we have already said, it is essential that we have an aquarium with the ideal characteristics for the species. Clownfish are oviparous and hermaphroditic . They present a laying ritual and this is more common in the spring.

When it comes to reproducing, which happens at approximately 2 years of age, the most dominant fish, generally the largest, will be the female . They will stick their orange capsule-shaped eggs on plants, rocks or a simple pot. Shortly before putting them on, we can see the wider female and both of them clean their environment. The males are in charge of their care and we will see them swimming around them, moving their fins to oxygenate the water. Their color will change and they will hatch in 7-10 days , at sunset.

The fry will consume live food and it is good to move them to another well-conditioned aquarium to prevent them from being eaten. Eggs can be moved. This is the stage that presents the greatest difficulty. Low light and a diet based on rotifer and brine shrimp are recommended . Both for this aspect and for any related to the care of these animals, we must always consult with experts. Finally, if we want to raise these fish at home, we must ensure that the specimens have not been caught in the sea to preserve the environment.

Breeding period

Female in the laying period with visible breeding buds

During spawning periods, it is difficult to distinguish between males and females, in fact some fish have the ability to change sex during their life as do the hawkfish or even the clownfish. . This phenomenon is called successive hermaphroditism . These sex changes significantly improve the chances of reproduction in fish.

Indeed the genitals of fish are located under their abdominal cavity, they are found in the same location in females and in males. In addition, their mass can sometimes represent a third of the total mass of the fish. During this period, we can observe the appearance of nuptial pimples on the head and gills of fish. Some species have a seasonal mode of reproduction, that is, their reproductive period varies with the seasons, while other species have mature and fertile ovaries throughout the year. Reproduction can only take place if there is sexual maturity of the fish.

Breeding seasons

Some species of fish reproduce two or three times a year to regenerate their offspring more easily. Spawners therefore choose a particular season and only reproduce during this period; however, they can spawn several times during this period. This is the case with Tilapia, which spawns all year round. The development of the gonadstherefore only takes place up to a certain stage, after which the sex glands remain at rest until favorable environmental conditions arise. The resting phase of the sex glands can last for several months. The arrival of the appropriate season then triggers the restart of gonadal development which ends with reproduction. Once this last phase has started, the development of the eggs cannot stop or regress. If the environmental conditions are not good enough to cause the final development of the eggs, the dormant phase continues until one of the environmental factors, oxygen or temperature for example, improves. If any of the factors worsen, the eggs begin the resorption process. The fish then has no chance of spawning that year.

In the wild, it often happens that the spawning of mature fish is abortive. If a river spawner evolves in a closed water environment, the latter’s gonads only develop up to a certain stage and thus remain dormant until resorption. It is a process that can be repeated every year without ever leading to spawning. In these fish, however, reproduction can take place by artificial induction of ovulation at the appropriate time. After laying, new eggs begin to form immediately and continue to develop until the dormant phase. By using artificial induction of ovulation, this same fish, which is a seasonal spawner, can reproduce two to three times a year.

Most freshwater fish spawn in the spring, others during flooding when water levels rise in rivers and lakes. Tropical and subtropical fish spawn during the rainy season, when spawning is most likely to survive in murky waters and fast currents.

Spawning Table

 Spawning method of fresh, warm and temperate water fish
Family Species Country / region of breeding Spawning mode
Acipenseridae Hybrid of Huso huso (Huso huso (beluga) and Acipenser ruthenus (Sturgeon sterlet)) Russia and Eastern Europe / Rivers Can be artificially propagated
Chanidae Chanos chanos (Milkfish) India and Far East / Sea of ​​the region No particular mode
Plecoglossidae Plecoglossus altivelis (Ayu) Japan / Seas and fresh waters Breeds in lower parts of rivers
Coregonidae Coregenus peled (Peled, “Syrok”) Russia / Siberian lakes and rivers Breeds in winter in deep water lakes
Coregonus lavaretus (lavaret) Czechoslovakia
Coregonus marena Breeds in winter in deep water lakes
Anguillidae Anguilla anguilla (Common eel) Europe / Coastal waters; streams and lakes Breeds at sea
Anguilla japonica (Japanese eel) Japan and China
Characidae Colossoma Venezuela, Colombia, Peru, Ecuador and Brazil / Amazon Basin Breeds in rivers
Anastomidae Leporinus copelandi (Piava) and other species South America / Rivers
Citharinidae Citharidium Breeds in streams
Catastomids Catostomus Commersonii ( sucker cyprin or North American carp) North America Breeds in river; spring spawning in shallow water
Ictiobus bubalus (small mouth buffalo fish) United States Reproduction on aquatic plants submerged in flooded land
Ictiobus cyprinellus (buffalo fish with big mouth)
Ictiobus Niger (black buffalo)
Cyprinidae Cyprinus carpio (common carp) Whole world Reproduction on aquatic plants submerged in freshly flooded ground or in ponds
Ctenopharyngodon idella (Chinese carp) Siberia and China No particular mode
Hypophthalmichthys molitrix (silver carp) Breeds in rivers
Aristichthy nobilis ( bighead carp)
Mylopharyngodon piceus (black carp) Malaysia / Vietnam / Thailand / Japan
Cirrhinus molitorella (mud carp) China / Taiwan / Thailand / Malaysia
Megalobrama amblicephala ( Wuchan’s bream) China / rivers
Parabramis pekinensis (White amour bream)
Catla catla (catla) Bangladesh / India / Pakistan / Burma / Nepal / Malaysia and other Far Eastern countries / rivers Reproduction in flooded areas
Labeo rohita (rohu)
Currhinus mrigala (mrigal)
Labeo calbasu (kalbasu)
Puntius ( Puntius javanicus , Puntius gonionotus , Puntius carnaticus ; Puntius belinka ; Puntius Ophoïdes and Puntius schwanefeldi ) Indonesia / Malaysia / Thailand / India / river and freshwater bodies Some species reproduce in rivers, others also in ponds, can be artificially reproduced
Tinca tinca (tench) Europe / India / Indonesia / Japan / Australia Breeds in ponds, can be artificially propagated
Tor tor (mahseer) India Breeds in rivers and can be artificially propagated
Osteochilus hasselti (nilem) Indonesia / Malaysia / Thailand Breeds in lakes and rivers
Siluridae Silurus glanis (large catfish, or glean, from Central Europe) Europe / Danube basin Reproduces in closed waters and artificially
Ictaluridae Ictalurus punctatus (spotted ictalure) United States and Central American countries Breeds in flooded areas
Claridae Clarias batrachus (magur) Thailand / India / Pakistan / Malaysia and Vietnam Breeds in closed waters; natural reproduction can be stimulated by digging holes 20 to 30 cm in diameter near the banks
Clairias macrocephalus
Clairias lazera Africa May recur by hypophysation
Heteropneustes fosilis (singhi) India and Pakistan Reproduces in ponds and also artificially by hypophysation
Pangasidae Pangasius sutchi (Pla swaï: Asian catfish) Thailand and Vietnam Breeds in river; can reproduce by hypophysation
Pangasius pangasius (Pangas) India Breeds in rivers
Esocidae Esox lucius (Pike) Europe and North America
Anabantidae Helostoma temmincki (kissing gourami) Far east Breeds in closed waters; Sexual maturity in 12-18 months, spawning every 6 months
Osphronemus (Olfax) Goramy (Giant gourami) India and Far East Pond in sufficiently deep ponds (1 m to 1.50 m), with submerged vegetation
Trichogaster pectoralis (Gouram “snake skin” or Sepat siam) Far east Reproduces in closed, oxygen-rich waters and submerged aquatic plants
Trichogaster trichopterus (Three-spotted aquarium gourami)
Mugilidae Mugil cephalus (mutt mutt) In many parts of the world Breeds at sea; induced reproduction possible by hypophysation
Mugil tade (mule) Pakistan / India and Indonesia / Red Sea and coastal waters Breeds at sea
Mugil dussumier (mule) India / Pakistan / Indonesia
Percidae Stizostedion (Lucioperca lucioperca); (Pike perch) Europe Pond on nests in closed waters
Stizostedion vitreum vitreum (“walleye”) North America Breeds in closed waters
Centrachidae Lepomis (sun perch)
Micropterus salmoides (largemouth bass) In many parts of the world
Sciaenidae Plagioscion squamosissimus North America
Cichlids Tilapia Africa / Asia / Americas Easily reproduces in closed waters, mouth incubation
Haplochromis mellandi Zaire and Zambia
H. carlottae
Astatoreochromis alluandi
Cichala Latin America Easy reproduction
Serranochromis Katanga (Congo) Oral incubation
Etroplus suratensis (“pearlspot”) India Spontaneous reproduction in freshwater ponds

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