Seasonal Activity and Feeding Pattern of Brown Trout (Salmo trutta) in a Dartmoor Stream in Relation to Availability of Food

Abstract

In laboratory tests, brown trout were most active between dusk and dawn from spring to autumn, but the percentage of the total activity that occurred during daylight was higher in the summer than in the other two seasons. Analysis of the variation in the weight of stomach contents during 24 hr in the three seasons showed a higher peak in weight at noon in summer than in the other seasons. The difference was related to an increased consumption of material of terrestrial origin, which other work showed to be most available to the fish between 09.00 and 12.00 hr. No relationship was found between the times of maximum occurrence of benthic and emergent items in the stream and of their consumption by trout. The increase in daytime activity during the summer was also evidently related to increased consumption of terrestrial material.