Facts about the animal kingdom

How Long is A Fish Pregnant?- Pregnancy in Fish

María Besteiros
By María Besteiros, Expert veterinary assistant and canine/feline hairdresser.. July 16, 2019
How Long is A Fish Pregnant?- Pregnancy in Fish

There are many different species of fish in the world, and if you have an aquarium at home, it is essential that you are up-to-date on all things fish related. The first thing you need to remember is that not all fish species can live together in harmony. In fact, the fundamental aspects of fish behavior will depend largely on the species.

Is your fish pregnant? If so, how long are fish pregnant for? Keep reading here at AnimalWised to discover everything you need to know about fish pregnancy, including fish gestation period and how to know if your fish is about to give birth.

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  1. How do fish reproduce?
  2. Fish gender identification
  3. Is my fish pregnant?
  4. How long is a fish pregnant?
  5. Is my fish giving birth?

How do fish reproduce?

Fish reproduction can occur in one of two ways, depending largely on whether fertilization takes place inside or outside the body. Fish can get pregnant on of the following ways:

  • Oviparous fish: fertilization is external, which means that the female first lays her eggs, which are then fertilized by the male outside of the body. Depending on the species, the eggs could be deposited on the bottom of the tank/ocean, float, stick to rocks or algae, shelter in nests or be carried on the body.
  • Viviparous fish: fertilization is internal, meaning that the male will fertilize the eggs inside the female’s body, The fry are born completely formed.
  • Ovoviparous fish: have another type of internal fertilization. After intercourse, the female will carry the eggs inside of her body, whereby the baby fish (fry) mature. These eggs will either hatch in the body or be expelled first.

In the case of internal fertilization, we refer to pregnancy in fish. However, it is important to note that when it comes to fish giving birth in aquarium, we need to be clear on what species of fish we are referring to as fish pregnancy will vary largely depending on the species.

For more, we recommend reading our article where we discuss how do fish reproduce?

How Long is A Fish Pregnant?- Pregnancy in Fish - How do fish reproduce?

Fish gender identification

In order for egg laying and pregnancy in fish to occur, it is essential that both male and female fish are present. Given the large number of fish species, there is no one rule to follow when it comes to differentiating between the sexes and determine the sex of a fish.

In some, fish gender identification is simple thanks to sexual dimorphism. Sexual dimorphism is when male and female fish carry physical and visible differences, allowing for easier identification. In some fish species males will be a different color or shape to females. When it comes to determining whether a betta fish is male or female, for instance, we know that females have noticeably shorter fins.

But, we have to also bear in mind that there are also hermaphrodite fish, that carry both male and female sex glands. Additionally, in other cases, fish are also sometimes born as one sex but develop into the other once they mature.

For more, we recommend reading our article where we take a look at the fish embryo developmental stages.

Is my fish pregnant?

So, what are the pregnancy in fish symptoms? Knowing whether or not a fish is pregnant can sometimes prove to be difficult. The most common confusions occur when food has been provided in excess and the fish fattens, or due to the anatomical conformation of some species. In oviparous fish, for example, what may seem as a pregnant fish, can actually be a sign of illness.

If you’re wondering,‘‘Is my fish pregnant?’’ You will need to analyze these signs in detail:

  • A bulk that grows under the abdomen
  • Its body shape will change shape
  • There will be a visible stain on the abdominal area, known as a gravid spot
  • In some fish, they may release eggs when you pick them up
  • In goldfish, males will chase the females

Remember that a fish reproduction depends on the species, not water temperature.

You may also be interested in reading our article where we discuss how do guppy fish reproduce?

How Long is A Fish Pregnant?- Pregnancy in Fish - Is my fish pregnant?
Image: pets.stackexchange.com

How long is a fish pregnant?

The duration of pregnancy in fish will vary depending on the species and living conditions. In some cases, gestation will last a month and the fry will be born already formed. While, in other species, fish gestation process may take up to two months, here are some examples:

How long is a guppy fish pregnant?

21-30 days.

How long are goldfish pregnant for?

Goldfish, technically, cannot get pregnant. When it comes to goldfish, females release unfertilized eggs into the water, whereby the male fertilizes them. It then takes between 2-7 days before the goldfish eggs hatch. This is the same case with betta fish, who’s eggs generally hatch after 3 days.

How long is a platy fish pregnant for?

Roughly 28 days.

Keep reading to find out how do fish give birth in a tank.

Is my fish giving birth?

So, how can you tell if a fish is about to give birth? Again, this too will depend on the species. Some general signs that a fish is about to give birth include:

  • A maximum increase in pregnancy bulge, which adopts a more square shape
  • In fish species with gravid spots, it may move towards the anal area
  • Noted nervousness
  • Rapid uncontrolled swimming

In the video by King Of Aqua (YouTube) below, we see how molly fish give birth:

If you want to read similar articles to How Long is A Fish Pregnant?- Pregnancy in Fish, we recommend you visit our Facts about the animal kingdom category.

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1 comment
Do I need to put my pregnant fish in a tank by her self till she haves her babys
Administrador AnimalWised
Hi Tammy,

Yes, it is a good idea to do so as the other fish will most likely eat the fry. In fact, once the mother gives birth, it is best to remove her immediately back to the other tank as she herself will eat the fry.
Image: pets.stackexchange.com
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How Long is A Fish Pregnant?- Pregnancy in Fish