During spawning season, a biological switch is thrown inside of fish, and they turn their thoughts to mating. Some fish (like salmon) swim all the way back to their childhood spawning grounds, while others spawn in their local pond or lake.
Females Grow the Eggs
The female fish grow unfertilized eggs inside their body for several weeks. A female will produce thousands and thousands of tiny fish eggs to increase the chance of fertilization. When she is ready, the fish will find a safe place to lay them, either in a gravel bed or somewhere that allows for sufficient cover.
Fertilizing the Eggs
During spawning season, the male fish seek out these nests of fish eggs that the female has laid. When they find one, they swim over the nest, and fertilize them with their semen. This allows conception to take place, and immediately the fish eggs start to become fish.