How Do Fish Reproduce?

Fish reproduce sexually through external and internal fertilization, but there’s so much more to the reproduction process, which we’ll discuss below in detail.

May 3, 2024By Monika Dimitrovska
how do fish reproduce

Fish don’t reproduce traditionally. In fact, these creatures have developed a variety of reproductive methods.

They reproduce sexually through external fertilization (releasing eggs and sperm into the water) and internal fertilization (depositing sperm into the female’s body). However, that’s just the beginning. Fish also have unique breeding strategies.

In this article, we’ll discuss fish reproduction in detail because understanding how they reproduce can help us manage fish populations, protect endangered species, improve aquaculture practices, and, of course, better understand our pet fish.

How Do Fish Reproduce?

freshwater fish babies
Image credit:

Fish reproduce through external or internal fertilization in three main ways, including oviparous (laying eggs), viviparous (giving birth to live young), and ovoviviparous (eggs hatch inside the female, then born live).

Additionally, they use various breeding strategies like scattering eggs, building nests, mouthbrooding, depositing eggs, or burying them in the substrate. Here’s a breakdown of each reproduction process in fish:

Oviparous Reproduction

Oviparous reproduction involves fish laying eggs outside the female’s body. This is a common method seen in many fish species, including salmon, trout, and catfish.

The process begins with the female laying eggs. Then, they’re fertilized externally by the male.

Viviparous Reproduction

In viviparous reproduction, low-maintenance aquarium fish like guppies and swordtails give birth to live young. Unlike oviparous reproduction, the fertilized eggs develop inside the female fish. When they’re fully formed, they’re born alive.

Ovoviviparous Reproduction

Ovoviviparous reproduction is a combination of both oviparous and viviparous methods, and it’s common in sharks and some eel species.

Here, fertilized eggs develop inside the female fish. However, they don’t hatch outside. They hatch inside the mother, then they’re born alive.

betta fish spawning
Image credit: Wikipedia

Fertilization Process

As we already established, fish can reproduce through external or internal fertilization.

External fertilization happens when eggs and sperm meet outside the body (in water). For instance, the female releases eggs into the water, and the male releases sperm to fertilize them.

Internal fertilization, as you can probably assume, involves the male releasing sperm inside the female’s body, where fertilization takes place.

However, unlike male seahorses that give birth, fish have various breeding strategies.

Fish Breeding Strategies

Fish also have various breeding strategies for keeping their offspring alive, such as the following:

  • Egg Scatterers: Species like salmon and trout release their eggs into the water column without parental care.
  • Nest Builders: Sunfish and bass construct nests, often out of plant material, to lay their eggs in. The male typically guards the nest.
  • Mouthbrooders: Cichlids and catfish carry their eggs or fry in their mouth for protection. They will hold them until they hatch. Or until they’re large enough to fend for themselves.
  • Egg Depositors: Carp and minnows lay their eggs on a substrate, such as rocks or vegetation. The male may fertilize the eggs after they’re laid.
  • Egg Buriers: Sturgeon and certain catfish species bury their eggs in the substrate, such as sand or gravel, for protection. The male digs a pit and covers the eggs.

Fish Reproduce Sexually

salmon eggs
Image credit: Wikipedia

Fish anatomy reveals that these unique aquatic creatures reproduce sexually by producing and fertilizing eggs and sperm. Additionally, they have specific reproductive organs called gonads, which produce and release gametes or sex cells.

Males have testes near the anus, which produce and store sperm, while females have ovaries near the ventral fin, which produce and release eggs. The reproduction process starts with courtship, where both males and females signal that they’re ready.

After mating, the male releases sperm into the water, fertilizing the female’s eggs. Then, they’re released into the water, where they develop into larvae.

How Do Fish Reproduce in Aquariums?

small yellow fish aquarium
Image credit: Nikhil Thomas from Unsplash

Fish reproduce in aquariums the same way they do in the wild. However, their breeding strategies depend on their species. Moreover, things like changes in seasons, diet, and how clean the water is will affect whether they will breed in aquariums and ponds.

In other words, fish owners should provide the right food and maintain a well-balanced aquarium for breeding fish successfully and preventing common pet fish diseases.

First and foremost, make sure they’re old enough and healthy. Learn about the type of fish you want to breed because each species has different needs. Generally, you should provide enough hiding spots and proper food and maintain the right temperature.

If you get these things right, there’s a high chance your fish will reproduce, and you will live in harmony with your aquatic friends.

goldfish eggs
Image credit: Wikipedia

If you have freshwater tank cleaners like mollies, swordtails, platys, or guppies, keep in mind that they have already fully formed babies.

You should keep them separate from the adult fish so they don’t get eaten, especially if you own fish that eat their tankmates and babies. You should also feed the babies small live or frozen food and crushed flakes.

To take care of the newborn babies, you might need to set up a special nursery. This can be a separate tank or something you buy. It should be like the big tank, with the right filter and water, and have enough hiding spots for the babies.

To make sure your fish breed successfully, just give them the right home and food. If you get it right, you’ll soon see healthy little fish swimming happily in your tank!

Closing Thoughts

colorful fish couple
Image credit: Juan Carlos Palau Díaz from Pixabay

In wrapping up, fish have various ways of reproducing, each suited to their environment. They lay lots of eggs, but only a few survive to grow up.

Males and females have their own roles, with some building nests and others taking care of the young. Some fish even go on long journeys to find the right place to spawn.

Overall, fish have fascinating ways of ensuring their offspring survive in the wild waters.

Monika Dimitrovska
By Monika Dimitrovska

Monika is a pet enthusiast and seasoned copywriter with a tech degree. She loves writing, but her heart belongs to her two mixed dogs, Buba and Bono, a mother-son duo. Bono’s siblings found loving homes, sparking Monika’s advocacy for neutering and deepening her curiosity about animal care.

But Monika’s pet family doesn’t end there. She also has two cockatiels and two rescue cats, proving her home is a haven for creatures big and small.