How Do Fish Mate?

There are different ways fish reproduce, and some of them don’t even need mates! Read more as we answer the question, “How do fish mate?”

How do fish mate? Some can do it alone.

One of the things I dislike is going to the dentist, but he has a cozy waiting room with a large fish tank that seems calming. Fish can be fascinating to watch, and the bubbling sound is melodic after a while, and this makes me forget about the unsettling investigation that is coming (maybe he’s onto something).

While waiting for my appointment, I overheard a child ask her mother about the fish. She asked if fish get married and have babies like people do, and I had to smile at how cute that was. Her mom wasn’t sure how to answer the question, but I imagine fish reproduction is not a usual topic for conversation. How do fish mate? There are a few ways.

Some fish can begin reproducing immediately after birth, while others may take years to mature. According to Sea World, the smaller the size of an adult fish usually indicates a fish that will reproduce early. Age and size are said to be the main factors in reproduction and reaching maturation.


In this mating method, the female is fertilized by one of the male’s fins and will expel the live fry about a month later. Put down the ketchup — it’s not that kind of fry! Fry is the term used to describe a recently hatched fish and may also be called larval fish.

The young are fully formed and are able to swim as soon as they are released. One of their first goals is to search for food. An example of livebearing fish are guppies. Interestingly enough, once a female has hatched fry this way, she is able to continue to reproduce without a male present.


Other types of fish reproduce by laying eggs. The eggs grow until and hatch into fry in about 7 to 10 days but can vary. Some fish known as egg scatters will do just as the name implies: They scatter their eggs in various areas while the male follows behind and fertilizes the eggs. The two fish will race around the tank to complete this task without stopping to feed.

Substrate spawners will leave eggs attached to surfaces with saliva. This happens with the female laying the eggs and the male following behind to fertilize them. Catfish use this form of mating. Bubblenest builders are a little different. The male fish blows bubbles and the female lays the egg in this “nest” of bubbles located near the water’s surface. The location allows for maximum oxygen and attracts a food source. “Mouthbrooders” describes an incubation period done by either the male or the female. After the female lays the eggs and the male fertilizes them, one of the parents will scoop up the eggs in their mouth and keep them there until the fry are hatched.

This video shows a female Betta fish laying eggs into bubbles that the male fish provided:

YouTube player

Party of One

Some species need only one to reproduce — themselves! Unisex fish can reproduce without the other sex present. Unisex fish are always female and reproduce only females. They do mate with males of similar species, but the sperm never contributes to the heredity of the offspring. You may be wondering why they bother at all, but I’ll leave that to your imagination.

Also Recommended: Which animals mate for life? (this is one of Petful’s most popular articles).

Hermaphrodites also exist in fish species. Some breeds of fish are born with both male and female reproductive organs, while others are born as one sex and change to a different sex later in the life span. Some fish types of sea bass (Serranidae) can be born females, change to males and change back to female later in life. It’s a girl! It’s a boy! It’s a girl again? Good thing fish don’t use baby registries, because that would be confusing!

Breeding for Profit

Breeding for profit can be a risky venture. Getting fish to mate in an aquarium can be extremely difficult, and there is no guarantee there will be a demand for your supply. Some pet stores or other business may offer store credit or cash in exchange for your fish, but there are such a large number of commercial breeders that they may not be interested. There is also the possibility that when your breed of fish finally mate, the store may not need or want them at that time. If you keep them for the beauty of the species, you are sure to receive a rewarding and comforting result.

Additional Resources

Photo: Gregory Moine/Flickr