[Diet composition and transition of clearhead icefish(Protosalanx hyalocranius)in Lake Xingkai]

Diet compositions of alien clearhead icefish(Protosalanx hyalocranius)in Lake Xingkai were investigated monthly from June 2010 through January 2011. Protosalanx hyalocranius preyed mainly on cladoceran, copepoda, shrimp, and larvae or juvenile fish. In June, P. Hyalocranius were smaller than 60 mm standard length(SL), and their diets were composed of zooplankton only. In July, fish began to appear infrequently in the diet of P. Hyalocranius larger than 60 mm SL, and by August fish was occurring in the diets of P. hyalocranius larger than 80 mm, 100 mm in September, and 120 mm in October and thereafter, respectively. The increase in the minimum SL of P. hyalocranius preying on fish within a given season reflects changes in resource availability, largely attributed to the corresponding increase in prey fish size as seasons progress. Protosalanx hyalocranius and Hemiculter sp. were the dominant prey fish in the diets of P. hyalocranius.