Consumption index is the total mass of recovered eaten organisms from residues found in the digestive tract to the body weight of the fish.

Consumption index is the ratio of the sum of the reconstructed masses of organisms comprising the food clump to the body weight of the fish. Feeding intensity can also be expressed as the percentage of fish feeding at the time of observation. Diet, or feeding rate - the amount of food consumed by a fish per unit of time (day, month, season, year).

Food consumption indices, for example, in roach larvae range from 0 to 142%; at later stages, maximum indices exceed minimum indices by 3-10 times.