The fact that some fish species are capable of laying up to several million eggs in one spawning is generally known. But why is such a huge amount of caviar needed?
Most fish species do not burden themselves with taking care of their offspring. Having gathered for the spawning ground, the females simply release their eggs into the water, and the males fertilize them. As a result, the percentage of surviving larvae is negligible. Of all the eggs laid by females, only 3-4 have a chance to turn into adult fish. The embryos become food for adult fish, die due to lack of oxygen, eggs dry up during low tides. Often the larvae are thrown ashore by waves.
It is clear that with this approach, a huge amount of spawned eggs is needed to preserve the fish population. Catfish and pike are capable of laying 100 thousand eggs during spawning, bream - 250 thousand. Burbot lays up to five, and cod up to nine million eggs at a time.
In order for the eggs of fish that do not care about their offspring to have a chance to survive, they are in a certain way adapted to the environment. In most fish spawning in fast currents, the eggs are sticky. This allows the larvae to stick to rocks, plants or soil, which allows them to remain in the aquatic environment.
Only a few species of fish show parental care for their offspring. Moreover, as a rule, males, not females, fulfill their parental duty.
Some males make special holes on the bottom, and invite females to lay eggs in them. After that, they carefully guard their offspring until the larvae hatch. The males blow fins on the eggs, remove the litter and dead eggs.
In other fish species, males go even further - they build real nests in shells, crevices and small caves. In some breeds, males simply store eggs in their mouths.
Due to this concern, the number of surviving fry is quite large. Therefore, just such types of fish are not particularly fertile - they can lay from tens to hundreds of eggs at a time.
