Ontogenetic dietary shifts in the summer feeding intensity of brown trout in relation to fish condition

Abstract

We examined condition factor, hepatosomatic index and stomach fullness in brown trout to study if feeding intensity can be related to fish condition. Trout were collected at three locations during the summer in temperate rivers (Galicia, NW Spain). Our findings suggest that the feeding intensity is inversely related with the fish condition because the stomach fullness decreases with fish age and size and the condition factor is the lowest in young-of-the-year (YOY). In general, no significant differences among age classes were found in the hepatosomatic index, except in one river (the River Lengüelle) in which YOY shows the highest value. The high feeding intensity of YOY during summer could be related with the increases in fish condition and survival in the later autumn and winter.