Do Fish Get Pregnant? How Can You Tell If a Fish Is Pregnant?

Pregnancies in animals are much different as compared to humans, especially in fish.

This might come as a shock to most people, but there are many live-bearing species of fish out there.

Do Fish Get Pregnant How Can You Tell If a Fish Is Pregnant? Not all fish get pregnant, but species such as mollies, guppies, platies, and swordtails tend to experience live births. There are many signs that indicate a fish is pregnant such as a protruding abdominal area or unusual behavior of the fish.

Betta Fish Life Cycle (Video)

To learn more about pregnancy in fish, keep on reading!

Pregnancy in Fish

Pregnancy can be literally defined as the period during which, after the union of eggs and sperms, developing embryos are incubated in the body. This term is usually used in the case of mammals but researched have used the term for animals that are not mammals due to the highly developed form of viviparity in eutherians.

There are actually five different modes of reproduction that can be classified based on the relations of the fertilized eggs and the parents.

  • Ovuliparity: The eggs are fertilized externally, and the babies develop externally too.
  • Ovoviviparity: The fertilization of the eggs takes place internally, and the fertilized eggs are retained either by the female or the male, but there are not many interactions between the zygotes and the parents. Feeding is excluded, but the maintenance of oxygen and water levels is done. The embryos survive on the egg yolk.
  • Oviparity: The fertilization of the eggs is internal, but the fertilized eggs develop externally as the eggs are rather large.

This is all explained in detail further in the article.


Viviparity is the retention and the growth of an egg that has been fertilized in the body of the mother until the offspring is ready to exist on its own. The growing embryo derives nutrition from the placenta or a similar structure. This is what takes place in most mammals and reptiles and some other organisms.

Another similar type of viviparity is known as ovoviviparity, which is commonly found in snakes and fish; it involves the egg being retained by the mother until it hatches. The embryo, in this case, derives its nutrition from the egg yolk, which is present in the egg, and it only depends on the mother for physical protection. Some common kinds of ovoviviparous fish include nurse sharks, sand sharks, requiem sharks, hammerheads, mackerel sharks, and some species of rockfish sculpins and Sebastes.

Experts and researchers commonly refer to these kinds of fish like livebearers, including mollies, guppies, moonfish, four-eyed fish, platys and swordtails. All these fish showcase some signs of pregnancy before the fry is born.

The female guppy, as well as the swordtail, will both give birth to about 20 to 100 live young after going through a gestation period of about four to six weeks. Mollies, on the other hand, will produce anywhere from 20 to 60 live young after going through a gestation period of six to ten weeks.

Fish Reproduction

Most fish reproduce via sexual reproduction. Sexual reproduction in fish involves the fusion of the sperm, which is produced by the male fish with the eggs produced by the female fish.

When it comes to fish, the male and female gender is a little complicated. Most fish species do have different individuals with separate genders, but there are some fish out there that are hermaphrodites. Hermaphrodites are individuals that have both ovaries as well as testes. Such fish can generally only produce one gamete, eggs, or sperm at one time, and their gametes must be cross-fertilized by another fish belonging to the same species.

Although there are also some hermaphroditic fish that are able to switch sexes, they can choose to switch between producing sperms or eggs in different reproductive cycles. For example, in Finding Nemo, a more realistic approach would have been that once Nemo’s dad lost his wife, he would have developed female sexual traits and mate with other male clownfish in later reproductive cycles. Other species of hermaphroditic fish include salmon and hamlets that are able to produce both sperms and eggs.

Another unique kind of reproduction found in some fish is parthenogenesis, which involves the female egg to develop into a fairly new individual without ever coming into contact with a sperm cell. In such cases that offsprings are replicas of their mother. This type of reproduction can be found in bony fish.

Male Pregnancy

When it comes to pregnancy and reproduction, fish are very peculiar creatures. There are many male fish out there, such as leafy sea dragons, seahorses, and pipefishes weedy among whom instead of the female fish the male is responsible for the incubation of the eggs before releasing the live fry into the surrounding water.

In order to carry out pregnancies, the male seahorse protects the eggs in a part of their body known as the brood pouch; the male sea dragons, on the other hand, attach the eggs to their leg while the male pipefish can do both.

After the eggs of the female gain maturity, she releases them from the trunk in her chamber using her ovipositor into the brood pouch or the egg pouch of the male, which is also sometimes known as the marsupium. This pregnancy does not really qualify as a bonafide pregnancy, as in mammals, the female provides the embryo food via the placenta, but this does not happen in the brood pouch. This might not be true for all species, as researchers have discovered that in syngnathid species that have well-developed brood pouches, sometimes males do provide osmoregulation, nutrients, and oxygenation to the offsprings that they carry.

When it comes to seahorses, the female seahorse is known to deposit around 1500 eggs on average in the pouch of the male seahorse, which is located on the ventral abdomen present at the base of the tail. The male seahorses develop pouches at the age of 5 to 7 months, and they carry the eggs for about 9 to 45 days until the baby seahorses are fully developed. At that point, they are still rather small in size. Smaller species may give birth to about five offsprings, while the large species might go as high as 2500.

The body of a male seahorse contains large amounts of prolactin, which is the same hormone that helps the milk production in pregnant mammals, and even though the male seahorse does not provide milk, it does offer oxygen and maintains a controlled environment.

Once the fry is ready to take on the world, the male releases them with muscular contractions, and sometimes it attaches itself to seaweed using its tail. The birth process generally happens during the wee hours of the night, and the female returns in the morning and finds that her mate is ready for the next batch of eggs.

Signs that Your Fish is Pregnant

If your fish is pregnant, there are many indicators that can help you evaluate the situation of your fish.

Here are some signs that you should keep an eye out for.

Protruding Abdomen

Keep in mind that a chubby belly does not always mean that your fish is pregnant; it could just mean that your fish is fat or overweight.

The belly of your fish won’t really seem swollen, just chunky. This is especially true when it comes to goldfish. If the belly of your fish is swollen, it’s bulging a lot and has pineconing scales, then that means that your fish is pretty sick and is not at all pregnant.

There are many other reasons for your fish to blow up, such as organ failure and abdominal infections. In order to make sure that your fish does not have pineconing scales, view your fish from above.

If your poor fish is sick, then it will seem much more swollen at the area behind the gills and also in the abdomen. Or your fish just might be fat and overfed. Overfeeding your fish isn’t such a good idea and could turn out to be fatal.

A protruding or swollen belly isn’t really a definite sign of pregnancy; your fish may look completely normal and still be carrying a large number of eggs.

Being Chased by Other Fish

Male fish only chase female fish when they think she is ready to breed. When the female fish is ready to release its eggs, it begins to release special pheromones into the water. The pheromones signal to the male fish that the female is in breeding condition.

Chasing might look like bullying to you, but it’s completely natural, and no one really gets hurt, so you really do not need to worry. This mostly occurs in the summer or spring months. Males tend to chase the female fish from behind and then nudge their bellies in order to release the egg, which he will then fertilize using its milt.

The male might even cause bites, scrapes, or other damage.

Eggs Released when picked up

Your fish is definitely pregnant if you pick her up, and then eggs start to come out of her as she wiggles in your hand. This also means that your fish is carrying loads of eggs and is in prime spawning shape.

A male fish might help her lighten her load. You should never try to squeeze to eggs out of the fish until and unless you are an experienced breeder as this could most probably put the fish under stress and inflict damage on the poor creature.

Lopsided Belly Seen from Above

If you are looking at a pregnant fish from above, then you will be able to see a lopsided belly; this usually occurs when one side of the belly carries more eggs than the other side of the belly of the fish.

Examine the Gravid Spot

The gravid spot is a red or black spot that can be seen on the abdomen of a pregnant fish near the rear vent. This is usually bright red or black in colors, and it becomes much more prominent over the course of the pregnancy.

This isn’t a definite sign of pregnancy as some fish always have this spot, but it will begin to grow lighter or darker once your fish is actually pregnant.

Fertilization and Spawning species

Fertilization in most fish species is external. Large amounts of sperms and eggs are spontaneously released into the water by males and females. The process of releasing the egg is known as spawning.

During spawning, what usually happens is that lots of fish of the same species get together, and they release large amounts of eggs and sperms at the same time. This ensures that the fertilization process is enhanced, and it also helps to ascertain that some eggs that have been fertilized will survive even if predators are close by. The chances of a predator consuming all the embryos are close to nil.

One of the greatest disadvantages of spawning is that there isn’t any paternal care of the young. Although there are some species that lay their eggs close by and do their best to guard them and protect them from harm. There are a number of fish species known as mouthbrooders, including cardinalfish, catfish, and jawfish, these fish brood their eggs in their mouths, which is quite obvious from the name. In most species, it’s actually the male fish that broods the eggs in its mouth to protect them from being eaten by predators.

How to Care for Pregnant Fish

The gestation period of most fish isn’t that long, and the time will pass away pretty quickly. Hence proper care is needed.

Just like a pregnant human, pregnant female fish also need high-quality nutrition, for themselves as well as their babies. They need to have enough energy to sustain her developing fry. However, the poor mother cannot really eat too much at one time as most of her abdominal space is taken up by the fry. This is where you come in. You need to provide the pregnant fish with three to five small meals throughout the day so that you do not overload the poor creature.

Just proceed by giving her a small pinch so that there isn’t much food leftover to foul the tank. The best thing to do is to offer the pregnant fish live or frozen brine shrimp on a daily basis along with flake of the highest quality. You can even add some freeze-dried bloodworms or spirulina flakes. The more variety you can offer the pregnant creature, the better nutrition she can get.

When the time of delivery closes in, you should separate the pregnant female from the community and add the creature to another tank. This will help the fish to lay her eggs in peace. Once the female has given birth, you should separate the mother and the fry as females are known to eat their own fry under stress.

Frequently Asked Questions

Can I place my pregnant fish in a glass jar?

No, you should always give her a separate tank so that the poor creature has ample space to move about.

How long is a fish pregnant?

Guppies are livebearers with a high profile, and they give birth between five to thirty fry, although under extreme circumstances, the female may only give birth to one or two or over 100. The gestation period, however, of a guppy is typically between 21 to 30 days, but this can vary considerably.

How many babies do fish have at once?

Different fish have a different number of babies. Fish like sharks have bigger wombs, bigger babies, but the number is less as compared to other fish. A female cod can produce up to 9 million eggs a year.

Do Fish Die after laying eggs?

Yes, some fish do die after laying eggs. Fish such as the Pacific Salmon die after depositing their eggs, and then these fish become a vital source of nutrition and food for the local ecosystem.

Where do fish eggs come out of?

In female fish, the eggs can be found in two ovaries, and they pass through the ovaries to an opening known as urogenital opening and then to the outside. In some fish, the fertilization of the eggs takes place internally, but they are shed before the development takes place.

What is the breeding season for fish?

The breeding season of fish extends from June onto July.

What is a pregnant fish called?

Twats and cowls are some common words used to describe pregnant goldfish, although you won’t be able to find these words in any dictionaries.

Do Guppies hide when giving birth?

Yes, they do, if your guppy begins to hide between plants or stays in the corner of the tank, then this is definitely a sign that your guppy is in labor and is ready to give birth. Hiding is not normal guppy behavior, so it’s very easy to notice. Just moments before giving birth, the guppy will distant itself from the rest.

Do sharks eat their siblings?

This isn’t common behavior for most sharks, but tiger sharks devour their sisters and brothers in the womb. The shocking part is that once the baby shark is done ingesting its siblings, it begins to consume all the living embryos, and then turns to the unfertilized eggs of its mother. This phenomenon is known as oophagy or egg eating.

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