Prey consumption rates and growth of piscivorous brown trout in a subarctic watercourse

Abstract

Prey consumption rates of piscivorous brown trout <i>Salmo trutta</i> were studied in the Pasvik watercourse, which forms the border between Norway and Russia. Estimates of food consumption in the field were similar to or slightly less than maximum values from a bioenergetic model. The piscivore diet consisted mainly of vendace <i>Coregonus albula</i> with a smaller number of whitefish <i>Coregonus lavaretus</i>. Individual brown trout had an estimated mean daily intake of <i>c</i>. 1·5 vendace and 0·4 whitefish, and a rapid annual growth increment of 7–8 cm year⁻¹. The total population of brown trout >25 cm total length was estimated as 8445 individuals (0·6 individuals ha⁻¹), giving a mean ± s.e. annual consumption of 1553880 ± 405360 vendace and 439140 ± 287130 whitefish for the whole watercourse. The rapid growth in summer of brown trout >25 cm indicated a high prey consumption rate.