Factors influencing predation of Hyperoche medusarum (Hyperiida: Amphipoda) on larvae of the Pacific herring Clupea harengus pallasi

Predation of different-sized Hyperoche medusarum (Hyperiida: Amphipoda) on larvae of the Pacific herring Clupea harengus pallasi was studied in the laboratory. The attacking rate of H. medusarum was a function of herring larvae size as well as size of the predator, and varied from 0.15 to 0.95 larvae attacked h-1 per hyperiid. In the range of 7.55 to 16.05 mm total larval length, vulnerability to predation was highest for 13.3 and 13.7 mm larvae. Large hyperiids swam faster and covered a wider area during searching and were more effective predators than small ones. Predation seemed to be influenced by light, and its intensity was dependent on the duration of previous food deprivation of the hyperiid.