How do fish reproduce and how are they born?

How do fish reproduce and mate?

How fish mate varies greatly depending on the species. They develop their reproductive organs at different ages, which largely depends on the size of the fish. The smaller the fish, the earlier it reaches sexual maturity. Some fish reproduce practically from birth, while others do so after several years. Moreover, some fish die after releasing their sperm or laying eggs, while others reproduce several times a year.

There are different types of reproduction in fish, which vary depending on the species. Mainly, there are oviparous, viviparous, ovoviviparous, and hermaphroditic species.

How do oviparous fish reproduce?

In the case of oviparous fish, this type of reproduction encompasses the majority of fish species. In this type, external fertilization occurs where the female lays eggs and the male fertilizes them by releasing sperm into the water. Thus, the embryo develops inside the egg but outside the mother. Depending on the weight and size of the fish, it will lay more or fewer eggs. For example, some fish release millions of eggs while others barely reach 50.

Within this type of reproduction, there are different methods. Firstly, there are egg scatterers. Here, the eggs are released in a specific location, and the male fish swims over them releasing its semen. The second method is egg burial, which occurs, as the name suggests, when the female buries the eggs for the male to penetrate the substrate and fertilize them. There can also be nest building using bubbles and other materials by the male. Once the male has constructed the nest, the female will lay her eggs in it for the male to fertilize.

In other cases, certain types of fish engage in a ritual where the female releases eggs into the water and waits for the male to release sperm onto them before collecting them with her mouth. Lastly, there are egg scatterers, a method that varies depending on whether the eggs are sticky or not. If they are sticky, they are placed in sheltered areas, and if not, they are placed in the water.

How do viviparous fish reproduce?

Setting aside oviparous fish, we encounter the second type of reproduction. Viviparous fish undergo fertilization and embryo development inside the female's body. This way, the offspring grow until they are fully formed within the mother, who nourishes them. When they are fully developed, the mother gives birth. Fertilization occurs through the male's anal fin or gonopodium, which releases sperm into the female.

How do ovoviviparous fish reproduce?

In the case of ovoviviparous fish, fertilization occurs in the same way as in viviparous species. The difference with this type of fish reproduction is that the mother carries an egg containing her offspring inside her, which use the yolk of the egg to develop properly, without needing to be nourished by the mother.

And hermaphrodite fish?

There are some fish that are neither oviparous, viviparous, nor ovoviviparous. There are species in which individuals change sex during their lifetime. For example, the parrotfish is born female and dies as a male. This is known as protogynous hermaphroditism. There are also cases where the fish is born male and dies as female, known as protandrous hermaphroditism. However, these fish always need a fish of the opposite sex to create life. Only synchronous hermaphroditic fish can release sperm and produce eggs simultaneously.

How are fish born?

Just like their reproductive methods, how fish are born varies from species to species. Some are born inside their mothers, while others hatch from eggs laid externally.

Viviparous fish, as mentioned earlier, develop inside the mother's body within a yolk sac that protects them. It's possible for the stronger offspring to consume the weaker ones inside the mother's body. In the case of oviparous fish, they hatch from the eggs in which they are found.

In some species, females care for the eggs until they hatch, while in others, males fulfill this role, and finally, there are species that pay no attention to the eggs.

Lastly, in ovoviviparous fish, the egg may hatch while still inside the female's body or at the moment of birth.