Fish Facts

Do Fish Lay Eggs or Give Birth?

Here is a list of egg-bearer or live-bearer fish, the number of their babies or eggs, their pregnancy, and the birth and egg-laying process.

Do Fish Lay Eggs or Give Birth? Yes, a fish gives birth and lay eggs in large number. Like all living organisms, the fish breed and reproduce babies to increase in number. Some fish are liver-bearers that give birth to babies, and some are egg-bearers that lay eggs. The usual counts of eggs range between 50 – 100000 in number while the number of babies ranges between 2-50. 

Do Fish Lay Eggs or Give Birth?

Fish-keeping hobby is full-time care and responsibility. Most aquarists and hobbyists breed them into their home tanks to increases their beautiful aquarium fish.

Getting information about the birth process and type of fish is necessary for every owner to keep the animal healthy and save the eggs and fry.

Fish never give birth to a single fry, or they never lay a single egg. The count varies, depending upon the species of fish. Before buying, an owner must know the reproduction type and the number of eggs or babies it will produce. So one can provide favorable conditions to a pregnant fish.

The egg-bearer fish are goldfish, danio, tetras, barbs, koi, killifish, betta, angelfish, catfish, and many others. The live-bearers are guppies, mollies, platies, swordtail, Endler, and mosquitofish.

Number of eggs or babies that some common fish lay or give birth to

Name of fish Lay eggs Give birth Number of babies or eggs Breeding level
Guppies No Yes 5 to 30 number of babies Easy to moderate
Goldfish Yes No Up to 10000 eggs Difficult
Zebra danio Yes No Up to 100 eggs Easy
Neon tetra Yes No 60 to 130 number of  eggs Moderate to difficult
Tiger barb Yes No Up to 200 eggs Easy
Koi fish Yes No Up to 10000 eggs Easy to moderate
Killifish Yes No 10 to 100 number of eggs Easy
Clownfish Yes No 100 to 1500 number of eggs Easy to moderate
Rainbowfish Yes No 20 to 60 number of eggs Easy
Diamond tetra Yes No 350 to 400 number of eggs Difficult
Betta fish Yes No 30 to 500 number of eggs Moderate
Angelfish Yes No 100 to 100 number of eggs Moderate
Catfish Yes No 4000 to 100000 number eggs Easy
Swordtail fish No Yes 5 to 80 number of babies Easy to moderate
Endlers fish No Yes 1 to 30 number of babies Easy
Platies fish No Yes 20 to 80 number of babies Easy
Molly fish No Yes 40 to 100 number of babies Easy
Mosquitofish No Yes About 60 babies Difficult
Eastern mosquitofish No Yes 40 to 60 number of babies Moderate
Corydoras fish Yes No 4 to 12 number of eggs Easy
Discus Yes No Up to 400 eggs Moderate
Gouramis fish Yes No Up to 600 eggs Easy
Pufferfish Yes No 6 to 8 eggs Easy
Oscar fish Yes No 100 to 1000 number of eggs Moderate
Rasbora fish Yes No 6 to 12 number of eggs Moderate to difficult
Kuhli Loach Yes No 500 to 600 number of eggs Difficult
Lionfish Yes No 12000 to 15000 number of eggs Moderate to difficult
Butterflyfish Yes No 3000 to 4000 number of eggs Difficult
Goby fish Yes No 500 to 800 number of eggs Easy
Cardinalfish Yes No Up to 90 eggs Easy
Filefish Yes No Around 300 eggs Easy
Cichlids Yes No 160 to 1600 number of eggs Easy

Egg-laying fish

Several aquarium fish are oviparous, and the fertilization of eggs takes place externally or internally.

Externally fertilized eggs

They lay eggs in large numbers and scatter them outside of the body into the tank where males fertilize them. Some will remain unfertilized, and some will die or damage even after fertilization.

Internally fertilized eggs

In some fish, the fertilization of eggs takes place internally. Despite internal fertilization, these fish lay eggs in the water. These eggs then hatch and release young ones.

Birth-giving fish

Few species do not lay eggs, and they give birth to the young ones or fry. Most birth-giving fish belong to the family Poeciliidae. The fertilization occurs internally through mating, and the eggs hatch insides the mother hence giving birth to off-springs. 

The development of the babies takes place inside the mother, and once they reach a certain maturity point, the mother gives birth. The mother nourishes the young ones internally and, after completing the gestational period, give birth.

How to know that your aquarium fish is pregnant?

Most people come to know about their fish’s pregnancy when they see many fry or eggs in their tank.

It creates problems for the owner, the fish, eggs, and newly born fry. There are some signs or behavior of fish that can help you identify that the pregnancy.

Chubby or extended bellies

One of the most prominent sign is the round, elevated or extended stomach of the female fish. It indicates that it is carrying a lot of eggs inside.

The live-bearers also develop a bulgy, boxy, squared shaped abdomen. Keen observation is essential to identify the pregnancy because a swollen stomach is also an indicator of illness. 

Release of eggs when picking or pressing fish

Sometimes when you catch your fish with your hand, you may observe that eggs streaming out, which means that it is about to release them. Immediate care and setup are necessary in this case as it can start laying eggs at any time.

Male chasing the female

Usually, the male chases the female fish that is about to lay unfertilized eggs. The males chase the female to fertilize the eggs once the fish lay them. There is a natural interaction between male and female at the time of spawning that helps you recognize your pregnant fish.

Lopsided belly

A pregnant fish may have an unequal filling of eggs in the body that means there may be more on one side. It makes the body looks lopsided, and you can get to know about it.

Red or black spot on the abdomen

Live-bearers develop a bulge in the abdomen in their gestation period with a distinctive red or black spot.

This gravid spot is visible toward the rear side of the fish abdomen. This spot brightens and becomes darker during pregnancy and can be dark-brown, olive-colored, or get black.

Fish try to hide or settle in the bottom

This behavior is typical in many other conditions and illnesses as well. 

It gives you a confirmation about your fish pregnancy when you co-relate it with other signs of pregnancy.

The pregnant fish try to hide in the tank or keep settling itself at the bottom. It becomes inactive and sluggish at the time of giving birth.

Change in eating behavior

Refusals and spitting of food can occur with a pregnant fish. Again this behavior does not relate to pregnancy only, but it is a consequence of many other illnesses.

All these signs help you to know that your fish is about to give birth or lay eggs. You must establish a separate tank and transfer it to the birthing tank so you can take better care of the mother, babies, or fry.

How do fish give birth?

The birth process is slightly longer and can take few hours, depending upon the number of fries. The time of the birth process is usually 6 to 12 hours, which can extend or shorten. 

Once the fry fully develops and mature inside the mother, the mother delivers them one by one. 

The fry is born in an oval or semi-round position, and the tails usually come out first. Sometimes, the fish takes a break or rest of few hours during the birth process. The fry remains still for a short period then starts swimming freely. 

The gestation period of fish that gives birth

These species have a typical gestation period, and they mostly give birth after the completion of this period. The average gestation period of birth-giving fish are:

  • Platy fish – 28 to 30 days
  • Guppies- 21 to 35 days
  • Swordtail – 28 to 30 days
  • Mollies – 26 to 28 days
  • Mosquitofish – 28 to 31 days
  • Endlers fish – 23 to 25 days

The platy, mollies, and swordtails give birth every month while others give birth in their breeding seasons.

Fry of fish

The fry is relatively large than the fry of egg-laying fish that is 1/4 inch long and start swimming once in the water. They are very similar to the adults as their fins are in normal-shape, and their overall appearance looks like a mini fish. 

They are usually few but are more active. These fries can protect themselves and do not require special feeding care like an egg-bearers fry. Also, some fry is unhealthy and die immediately after birth.

How do fish lay eggs?

The egg-laying process is easy and less time-consuming as the mother lay all at once at a safe place. The male then goes to the eggs and fertilizes them. Some fish lay sticky eggs that attach to plants and other surfaces, and some scatter in the tank. Killifish releases into the substrate to protect them. 

Some fish takes the eggs into their mouth to protect them, and these are cichlid and gourami. Siamese fighting builds a bubble nest from saliva. 

Eggs and fry of egg-laying fish

The eggs are pelagic or demersal, which means they will either sink in the tank or float on the water. The pelagic-eggs are light-weight that keeps them floating in open water. The demersal have more weight that makes them sink or rest in the bottom of the tank. 

The size of the fry that hatches out is comparatively smaller than the fry of live-bearers. They do not need instant feeding after hatching because of the reserves.

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