Before incubation the eggs are fertilized by the wet, dry, or semidry method. In the Russian method, mature eggs and sperm are "strained" by lightly pressing the abdomen of a fish with the fingers; then the eggs and sperm are carefully mixed and moistened with water to activate movement of the spermatozoa, which is when fertilization takes place. The fertilized eggs are incubated in a body of water (nonplant method) or in fish-breeding plants (plant method).
The sticky eggs of fish that spawn in the spring (Acipenseridae and Cyprinidae, for example) and, in a few cases, the eggs of fish that spawn in the autumn (Salmonidae) are incubated by the nonplant method on a substrate (branches of juniper and spruce, washed rootstocks of willow and cane, baskets with branches) or in fish-breeding apparatus set up in a body of water. The substrate, with evenly distributed eggs adhering to it, is attached to the bottom of the pond and left there until the embryos hatch. The most frequently used of the fish-breeding apparatus in the nonplant method are the Chalikov apparatus, which are attached to one another and set up where there is a current. The length of the incubation period of eggs of fish that spawn in the spring is several days; of fish that spawn in the autumn, it is several months. Depending on the purpose for which they are to be used subsequently, the hatched embryos are raised to certain dimensions in special pools or ponds.
