You have probably seen some of your female pets developing a bulge in the belly sometimes. Maybe even walked them through the process.

Yet, some of us have no idea how the fish reproduce.

You know how we do it already. I get you the information while you sit back and enjoy.

Fish can get pregnant. And the weird thing is, some male fish are not left out in this task of pregnancy.

Only a few of the male fish species can be pregnant, though. They are pipefish, seahorse, and the sea dragon.

can fish get pregnant

When you read further, you will learn how to identify a pregnant fish, the way they mate, their gestation period, and whether all fish lay eggs. 

There’s a wealth of knowledge that awaits you!

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Mating is the coming together of both male and female species of an animal for reproduction.

This act of mating is commonly called copulation.

All animals have different ways of alerting the opposite sex that they are ready for mating and reproduction.

Male fish attract female partners through various ways like; making inviting sounds, dancing, drawing patterns on the ocean sand, building nests, etc.

On the other hand, female fish attract partners for mating by spreading out their fins or nesting to send a signal to the male fish.

Nesting can be done either by the male or female fish. The point is to arrive at one goal, which is mating for reproduction.

Types of Mating in the Fish

Most fish species prefer fertilization occurring outside the body, while some others prefer fertilization of eggs occurring within.

Most egg-laying fish prefer external fertilization where the available male releases its sperm on the already released eggs.

Fish that fertilize internally are; swordfish, platyfish, and horn sharks. At the same time, those that fertilize outside the body are; trout, salmon, and starfish.

  1. External Fertilization

 Here, the fish releases her eggs into the sea for the male to fertilize. This process is termed spawning.

The spawning period usually lasts between 2-3 days.

When female fish are ready to spawn, they prepare an area where the eggs will be deposited.

They can either make a sort of nest, find a hidden place with an entrance to release the eggs, or randomly deposit them in the water.

When you notice your fish being chased around by the male species, look closely. It must be time for it to spawn.

When the females are ready to release eggs, the chase is meant to encourage them, the male fish.

A male counterpart is always nearby to fertilize the released eggs almost immediately. Within a week, the eggs begin to hatch, bringing forth fry, who then go off on their own.

  1. Internal Fertilization

Some other species of fish prefer for this fertilization to occur within. 

They need to engage in copulation with their male counterparts for fertilization to take place within the body.

Then, the eggs are released into the water already fertilized, or the fry can come out of the parent’s body fully formed.

Some fish’s mating process, like the shark, can look aggressive if you’re not used to it.

The males usually use their teeth to hold onto the female while inserting an organ called a clasper into the female’s cloaca.

Some other fish species transfer sperm through the fins while holding onto each other.

How to Identify a Pregnant Fish

You must be curious then to know if your fish is already pregnant? 

Identifying a pregnant fish is a simple task some find difficult because they are only looking out for a bulge in the belly.

That bulge in the belly can be misleading. It can either be a sign of an overweight fish, water retention due to excessive salt, or an infected fish.

Other factors can help you determine the condition of your fish. What you need is an eye for detail and knowing the difference.

If you have an aquarium or a fish pond, you may have to pick the fish up and check for these signs by yourself or look closely.

Sometimes, the symptoms of pregnancy in egg-bearing fish vary from symptoms in live-bearing fish.

This is only because these fish have different breeding methods. Yet they all point to one thing- a pregnant fish.

Symptoms of Pregnancy in egg-layers

  • Swelling around the abdomen
  • Nesting, that is to say, the fish is preparing a spot to lay the eggs. That is a sure sign of pregnancy.
  • For the fish who breed eggs in their mouths like the goldfish, you can find eggs when you open their mouth.
  • More significant and slower in swimming.

 Symptoms of Pregnancy in Livebearers

Gestation Period of The Fish

The gestation is the period between the fertilization of the ova (which are the female egg cells) and the egg/fry development. 

It is the entire period of pregnancy.

The duration of pregnancy varies from fish to fish. You can then understand it better if we grouped the fish in the egg-bearing and live-bearing categories.

Egg-bearing fish: gestation period is about 2-8 days for the eggs to develop fully.

Live-bearing fish: the average duration of pregnancy for live-bearing fish is between 4-10 weeks. 

Again, the fish in this category may not have the same gestation period. What makes them alike is that their duration of pregnancy must fall between 4 to 10 weeks.

When a fish is about to spawn, it becomes much more significant than its initial size. This pregnant fish can be called “a berried fish.” It is named that way because, at that time, the abdomen is filled with eggs ready to be released.

Do All Fish Lay Eggs?

You see, the fish species are diverse. You cannot find them following a single pattern.

The answer to the question above is no. Not all fish lay eggs. In previous headings, I classified the fish as egg-bearing and live-bearing.

Now, I’m going to call them by their scientific names, so you get a picture of what you’re dealing with.

  1. Oviparous Fish:

The oviparous fish lay ripe eggs (whether fertilized or not) in nests or randomly into the sea for those eggs to complete the process of development outside the body.

These fish do not sustain the eggs with nutrients from their body.

Some species of oviparous fish are:

  • Salmon
  • Goldfish
  • Bluefin tuna
  • Rainbowfish
  • Angelfish
  • Betta
  • Paradise fish
  1. Viviparous fish:

The species under this group give birth to their young ones alive. After the sperm of a male fish fertilizes the ova during copulation, the egg begins to develop within the 4-10 weeks of pregnancy.

Thus when the fish gives birth, her young ones come out alive.

Some species of viviparous fish are:

  • Molly fish
  • Swordtail
  • Mosquito fish
  • Guppy
  • Sharks
  • Platy
  • Cichlid
  • Seahorses (male)
  • Pipefish (male)

The Process of Birth

The fish can give birth through the mouth of an opening called the genital papilla behind the anus.

The process of giving birth is not a difficult one for the fish. It comes naturally to them and without pain as it appears.

The egg-bearing fish can release from 100 to 1,000 eggs in one spawn.

But this mass reproduction style is dangerous to the eggs as most of them end up eaten or unhatched due to lack of proper nutrition.

On the other hand, live-bearing fish do not pop out all their young ones at once. It takes time for the fish to release the fry, one after another.

Different species of live-bearing fish can give birth to any amount of fry in a single pregnancy. But it usually falls between the range of 20-200.

It’s important to watch closely when your fish gives birth, then immediately move the eggs or little fry away to another tank.

The parent fish and other predators are likely to eat the young fish before they even have a chance to mature.

Some fish eat their eggs/young ones not just because they are cannibals but also;

  • there is a lack of food
  • too much noise around the pond/aquarium
  • to get rid of badly formed eggs and
  • to reduce the quantity of the eggs

In conclusion, you have to remain alert to notice the slightest change in any of your fish.

Learn and understand the signs of pregnancy in all your fish species. They do not all follow the same pattern.

This will help you take better care of them during pregnancy and protect the young ones from being eaten after birth. Hence, providing you with healthy and happy fish for your tank!