How Do Fish Reproduce? Fin-tastic Fish Breeding Facts For Curious Kids

Joan Agie
Oct 23, 2023 By Joan Agie
Originally Published on Nov 05, 2021
Multi colored platinum guppy fish
Age: 3-18
Read time: 9.2 Min

You might have noticed a group of little fishes swimming around with their fins swaying in the water.

It is a beautiful sight to see tiny cute little fishes. But how do these cute little ones end up being formed?

The breeding and mating process among fishes is a different story. To be exact, they reproduce differently. But the one common factor in these varied methods is the reproductive organs.

The organs involved in reproduction are the same but the way they work is different. For some fish species, the eggs hatch, and for some others the babies are born. The reproductive organs are the common factor in this varied mating and breeding.

Some fish have a nest while some others have mouths to guard the egg. How do the fish species mate?

Do they need to be at a certain age when they mate? The fascinating world of the fish’s reproduction is worth knowing, so let us get right to it. Afterward, also read about how long do hamsters live and bobcat vs mountain lion.

How do fish make their babies?

You might have noticed little fish babies swimming through the water. How do female fish give birth to these tiny babies? As you might be aware, reproduction is a vital part of the living world. To keep a species alive, all creatures need to reproduce and create young offspring.

The case of the species of fish is no different from this. They need to reproduce and create baby fishes so that as a species, these fishes would not end. So, how do the fish make babies?

Firstly, how the fish reproduce mainly depends on the species of fish. Each species of wild fish has different ways of fish reproduction in freshwater as well as saltwater. Normally, the female fish will lay eggs in the water.

These eggs are then fertilized by the sperm of males. After the female fish lays eggs and the sperm of the male fish fertilizes the eggs, new young ones are given birth.

This type of fish reproduction is seen in oviparous fishes. Oviparous fishes are those species of fishes that lay unfertilized eggs instead of fertilized eggs. This is one common mode of reproduction seen in fish species.

In other cases, the eggs are fertilized before they are released into the water. This is not as common as oviparity but is still a mode of reproduction among species of fish.

The fertilized eggs are released into the water from the mother’s body and the young ones hatch out from these eggs. Another mode of fish reproduction is where fertilization happens inside the mother’s body; the male and female mate together and then the eggs are fertilized. The young ones are born from the mother’s body instead of having eggs.

This type of fertilization is seen in rays, sharks and some species of guppy fishes. These are the common modes of reproduction among fishes.

But is it true that the fishes die after giving birth? Not really, as you already know, fishes reproduce in these three ways. The tropical fishes that you have might also reproduce in these ways.

There is a slight chance that when fishes give birth, due to complications in labor, they could die. But this doesn’t happen for all the fish species. On the other hand, fish species like salmon die after fertilization.

After the females spawn with males, they will die. Females may live for a week or two and guard the nests after spawning. But usually, after the spawning process, they are too tired to stay alive anyway.

How fast do fish reproduce?

Normally, you might have noticed young offspring of a fish during a certain period. The fish that we eat tends to have babies in it during a particular season. Is that the same for all the fish around the world? Do the fish live young and reproduce only during a certain period?

To tell the truth, the mating and spawning of fish will vary depending on the species. The reproductive period of some fish groups will be for a particular time while others undergo the process all throughout the year. If that is so, just how fast does a fish reproduce?

Depending on the different breeding methods, the time taken for the reproduction may also vary. The reproductive cycle in each species of fish is different. Some species of fish spawn throughout the year. They have no specific period for their spawning and breeding.

Clownfish, guppies, mollies are examples of it. Some only reproduce during a particular season. Many of the wild fish in the sea is seen to show this behavior. They have a specific time of the year during which mating and spawning happen.

There are also some other types of fish species where they mate only once. They only mate once because, after these species mate, they tend to die. Salmon is a big example of that.

Salmon during their breeding season undergo spawning. The female will spawn over riverbed depression and the male will release sperm into it. After spawning, the salmon species die within a few weeks. If the species don’t die, they can spawn upto one or two times.

But normally, these salmon species tend to die. The salmon species are born in freshwater and later go to saltwater to live. For the spawning, they return to the freshwater.

The time for the young ones to come out is also different, which is an obvious fact by now. The egg of some fish like koi will hatch within two or three days.

Goldfish is an example. Contrary to this, for the fish that give birth to the young ones, it might take upto three-four weeks for the process.

The mature fish will fertilize the egg and undergoes a gestation period in this case. The unisex fish and hermaphrodites among the fish species undergo different reproduction. For the unisex species, there is no need for sperm while that is not the case for hermaphrodites.

Hermaphrodites are also unique species of fish that can change their gender. The clownfish is an example of hermaphrodites.

Multi colored platinum guppy fishes

How many eggs can a fish lay?

So fish reproduce in mainly three ways. In each of these different modes of reproduction and fertilization, how many eggs do they lay? Some fishes can lay a number of eggs while others may not be able to do so. Wild fishes lay eggs when they are sexually mature.

Depending on the mode they reproduce, their eggs can be many or few. How will we determine which is which? To be honest, it is easy to figure out which fertilization can have many eggs and which few ones.

That’s right. Fish can reproduce without mating between the male and female.

The young ones hatch outside the body of the females. In this case, females can lay large amounts of eggs because well it is not as hard as mating with the males and keeping an embryo in the body. The number of eggs that the females can lay in this spawning season is called fecundity.

The size and age of the fish are what determine it. Some fishes like mola or ocean sunfish can lay as much as 300 million eggs while some others lay around 50-250 eggs per season.

But in the case of viviparous fishes, that is fish that reproduce internally, it is hard for too many young ones to live inside the body of the fish. In these types of fish, the number of eggs is fewer compared to the oviparous fish.

In fishes that undergo fertilization internally, there are two modes, one where the eggs are fertilized internally and one where the young ones are given birth.

In the case of eggs fertilized internally, the fish need not provide nutrients for the development of the young ones.

The nutrients needed for the development of the eggs are provided by the egg yolk itself. But when fishes give birth to the young fishes, all the nutrients needed for the growth and development are given by the females.

In this type of development, the female fish need to take care of themselves and the young ones. Some fishes lay eggs unguarded. The oviparous fishes who lay many eggs usually leave these eggs unguarded.

Some other fishes will create a nest where the male and female place the eggs and guard them till they hatch. In some unique cases, fishes keep the eggs in the mouth till they hatch. Cichlids and catfish are examples of fishes that keep the fertilized eggs in their mouth.

What to do if my fish has babies?

If you own pet fishes, they are bound to have babies of their own at some point in their life. What is the process of taking care of your pet fish and the babies? Although it is a hard process, if you take care of some basics, the whole process will be more manageable.

Although it may seem weird, some fish species will eat their young ones. This practice is seen among the fish group.

So if your pet fish just had babies, it might be a good idea to keep them apart from the adult ones for their survival. When you separate these baby fishes, keep in mind not to introduce new water to them.

Since they are not yet accommodated to new water conditions, it is best to keep the water that they were in before.

This way the babies don't get too uncomfortable and eventually die of the discomfort. It is possible sometimes. That being said, some parent fish will guard the nest of the babies.

If you see the parent fish guarding the nest against other adult fish, then it could be safe to keep them with the parents. The parents will take care of their young ones. The new young ones are weaker compared to the mature ones.

So it is important to take care of them. Make sure the water is not too contaminated. The nitrate and ammonia levels in the water should also be kept a close check on.

When young ones are born, they need food to eat too. Some fish species prefer live food when they are young.

It is also important to clean the remnants of food items from the tank because the water will end up being contaminated by the food particles. Raising a baby fish can be a mighty task sometimes. Depending on the mode by which the fish reproduce, the number of eggs can be different.

The number of fish born out of the fish can also be varied in number. It is better to choose livebearers as your pet fish. In that case, the young ones born are few.

If you have an oviparous fish for a pet, the task is hectic since they produce many eggs. It is better to be careful and cautious when choosing the fish that you need as a pet.

Here at Kidadl, we have carefully created lots of interesting family-friendly facts for everyone to enjoy! If you liked our suggestions for how do fish reproduce? fin-tastic fish breeding facts for curious kids then why not take a look at bear diet: curious diet facts on different bear species for kids or anglerfish facts?

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Written by Joan Agie

Bachelor of Science specializing in Human Anatomy

Joan Agie picture

Joan AgieBachelor of Science specializing in Human Anatomy

With 3+ years of research and content writing experience across several niches, especially on education, technology, and business topics. Joan holds a Bachelor’s degree in Human Anatomy from the Federal University of Technology, Akure, Nigeria, and has worked as a researcher and writer for organizations across Nigeria, the US, the UK, and Germany. Joan enjoys meditation, watching movies, and learning new languages in her free time.

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