Life Cycle of a Fish

When I was young, my parents took me to a carnival. There was the typical rides and games, and you needed tickets to do anything. My parents let me play a game where I could bounce a ping pong ball on a bunch of open fishbowls and if it landed on a colored one, I won a prize. I won the prize, and it turned out to be a goldfish.

Goldie, as he was called, was my first pet and my first experience with fish. Goldie didn’t last all that long – and I found out later that my parents had done that whole “replace the pet while she’s at school” bit at least once. But even if I didn’t get to spend a lot of time with Goldie, he made a lasting impact on me and sparked my love of fish.

My parents, bless them, encouraged me. My mom took me to the library and let me check out the same book about taking care of fish. I knew that book by heart! There was one section on the life cycle of the fish, and I still remember it to this day. It’s actually pretty interesting.

Everyone knows that fish come from eggs. It’s kind of amazing how the process works, and that it even works at all! When they are spawning, female fish release eggs into the water. Depending on the species, they might have what’s considered a nest, but not all do. Male fish release something we call milt, which fertilizes some of the eggs.

Many eggs don’t even make it to maturity. Between environmental conditions, disease, and predators, most fish eggs don’t stand a chance. Those that do hatch feed from an attached yolk sack during their larval stage. Sounds kind of gross, doesn’t it? This helps fish survive, because unlike many other creatures, there are no parents around to care for them. Once the yolk sac is absorbed completely, the fish moves out of the larval stage and enters the fry stage.

That’s right, young fish are called fry!

Fry can find their own food sources and their whole job is to eat and grow. They’ll stay a fry for anywhere from a couple of months through about a year, depending on the species. If they make it past that, they become juvenile fish. This is essentially a fish’s tween years. Once they are able to reproduce, they become adults. For fish with short life spans, they can reach this mark in a year. Fish who live for longer periods, like the sturgeon, don’t hit this point until about 25.

It really is an interesting subject. There are so many things that have to work out just right in order for the egg to be fertilized, for it to survive long enough to hatch, then sustain themselves on the yolk sac as larva, and then somehow to make it through the fry and juvenile stage. One of the things I want to do is study these different variables and see what we can improve for fish whose species are threatened by extinction, especially those who play a large role in their habitat’s ecosystem.