Demand-feeding behaviour of rainbow trout

Abstract

Rainbow trout learned quickly to operate a trigger to deliver dry food and showed a peak of feeding at dusk, but also appreciable nocturnal feeding. Food deliveries were aggregated into feeding bouts with a preferred time between trigger presses of 4–8 min; the aggregation of feeds was more marked in groups of trout than with trout held singly. Total daily food intake varied with the reward level per trigger press, and could therefore be controlled at about the manufacturers recommended feeding levels. Territorial and hierarchical behaviour were observed and in groups of up to 20 trout only one member of the group pressed the trigger although all the fish took the food delivered, and there was no evidence that smaller fish in a group were deprived of food to the point at which they lost condition.