Nutrition is one of the most important functions of the body. The main functions of the organism - development, growth, reproduction and all other energy processes occurring in the body - are carried out at the expense of substances coming from food. The size and qualitative state of a fish stock is determined by its food supply.

Food availability - determined by ecological, morphological and behavioral characteristics of fish and food organisms (distribution in the water column and the ground, the presence of protective devices, speed of movement, the presence of shelters, etc.), as well as by hydrometeorological conditions that ensure the availability of certain areas of the reservoir, which are rich in food.

The feeding rhythm of fish depends on the availability of food objects, their size, caloric content, method of extraction, time of day, etc. Intensity of feeding during a day depends on food availability and energy consumption for its extraction. Predatory fish, eating large prey, at the same time ingesting a lot of food, and its digestion period stretches over several days. Peaceful fish eat a little, but more often, taking food in 4-6 hours.