Seasonal variation in food preference of the brown trout Salmo trutta macrostigma (T., 1954) from Uzungöl Stream, Turkey

The present study is aimed to provide information on the abundance of natural foods of Salmo trutta macrostigma (T., 1954). Fish were captured from Uzungol Stream in Trabzon, Turkey between March 2009 and May 2010. It was investigated whether the dietary preferences of trout (S. t. macrostigma) change on account of seasons. Captured fish were measured 17.11 ± 4.65 cm (S.D.) (range 5 to 30 cm), 60.38 ± 48.52 g (S.D.) (range 2.34 to 250.84) (n = 163), respectively. The condition factor of trout calculated 1.00 ± 0.5 (S.D.) (range 0.57 to 1.58) (n = 163). The age range was between 0 and 8 years old. Stomach contents were analyzed using two methods, the frequency of occurrence and numerical method. A total of 11 prey groups were identified in the diets of brown trout living in Uzungol Stream. Prey groups were consisted of Trichoptera, Clitellata, unidentified Insecta, Coleoptera, Ephemeroptera, Haplotaxidae, Diptera, Verenoide, Plecoptera, Hymenoptera and Arachnidae. Analyses of stomach contents showed that the trout feed basically on Arthropoda and Annelidae. Seasonal variation of different food items showed that a high percentage of occurrence of Clitellata were recorded during both winter and autumn, while the highest percent of Coleoptera occurred during summer.