Spawning is the process of hatching of sexual products by fish, carried out at night (burbot) or early morning and evening (shuka, bream, roach). It is accompanied by a change in the behavior of fish, as well as their appearance. The signal for the beginning of spawning is the presence of certain environmental conditions (temperature, water salinity, oxygen content), spawning substrate and the presence of individuals of the other sex. In most fish, fertilization and development takes place in the water, outside the mother organism.

Spawning ground - an area of a water body (watercourse) with certain environmental factors, where fish reproduction takes place. It provides the species with the most favorable conditions for the development of eggs and milk.

Usually occurs in specific locations (spawning grounds). Many fish have mating attire during spawning. Some fish (passage fish) go from the sea to rivers (salmonids, sturgeons) or from rivers to seas (river eel) to spawn.

Fishing may be prohibited during spawning. After laying eggs in some groups (e.g., salmonid fish), the parents die. Some groups of fish (in particular, many perch) show care for the offspring - protect the eggs and larvae that have emerged from it. Representatives of the family cichlhovyh protect and fry. Most species of fish do not care about offspring and in aquarium conditions eat their own eggs.

Freshwater fishes are distinguished as lithophilic, which lay eggs on rocks (sturgeons, salmonids, etc.), phytophilic, which spawn on vegetation (carp, bream, etc.), and pelagophilic, whose eggs develop in the water column (fathead minnow, coho, etc.). Marine fish lay pelagic or bottom spawning eggs. Each fish species spawns under certain conditions (water temperature and salinity, appropriate substrate, etc.). In cold and temperate waters, spawning occurs once a year - in spring, summer or fall. In the tropics, spawning seasons are weaker or not pronounced (there are examples of year-round reproduction).