EVALUATION OF THE PREDATIOIN AND FEEDING SELECTIVITY ON BOSMINA LONGIROTRIS BY POND SMELT USING IN LAKE HACHIRO

Abstract

 Dietary utilization of cyanobacteria by B. longirostris is expected to suppress cyanobacterial blooms. We investigated the stomach contents and fatty acid compositions of the pond smelt (Hypomesus nipponensis) to examine the predation on B. longirostris and to evaluate feeding selectivity in Lake Hachiro, Akita. As a result, we found that the main dietary sources of the pond smelts were B. longirostris which accounted for 90.2 % of the total stomach contents of the pond smelts during the summer when cyanobacterial blooms were observed. In particular, B. longirostris were selectively preyed by the pond smelts less than 5 cm. Predation of B. longirostris by the pond smelts was also supported by the increase of cyanobacterial fatty acids in B. longirostris and pond smelts in summer. These results indicate that catching the pond smelts would contribute to decrease the predation pressure on B. longirostris, consequently the effects of suppressing cyanobacteria is strengthened.