Investigations on the Feeding Ecology of Ohrid Belvica (Salmo ohridanus)

The feeding ecology of Ohrid Belvica was studied based on the species composition of dietary components, their relative importance, and seasonal variability in Simpson’s diversity index. Qualitative analysis confirmed the presence of 45 trophic elements, of which 39 were planktonic and benthic hydrobionts, while six represented life stages (eggs, larvae, and imago) of some of these organisms. Planktonic crustaceans (mainly Daphnia, Cyclops, and their eggs), larvae of Chironomus (Insecta), adults of Limnodrilus (Annelida), as well as eggs, larvae, and adults of Alburnus (Pisces), constituted the main components of the diet of the Ohrid Belvica stock. The highest frequency of trophic elements in the diet was recorded in spring (n = 43; F% = 93.6), while the lowest value of feeding intensity was observed in autumn (n = 21; F% = 46.7). The average annual value (M ± SD) of the species diversity index (Ds), characterizing the diet of the Ohrid Belvica stock from the Albanian part of Lake Ohrid, was 0.721 ± 0.068 (Var% = 9.44). In addition, annual variability in three organo-somatic indices (RGL, VSI%, and HSI%) was assessed. The mean values of these parameters for the Ohrid Belvica stock were VSI% = 10.764 ± 1.735, HSI% = 1.152 ± 0.224, and RGL = 0.849 ± 0.072.