CANNIBALISTIC FEEDING-BEHAVIOR OF THE BRACKISH-WATER COPEPOD SINOCALANUS-TENELLUS

Cannibalistic feeding behavior of the brackish-water copepod Sinocalanus tenellus was examined in the laboratory using CI-II, CIII-IV and CVI female as predators and NI-II, NIII-IV, NV-VI and CI-II as prey. In each prey-predator combination, the ingestion rate increased with increasing prey density to an asymptotic value. Cannibalism took place even when phytoplankton was available as an alternative food supply. Based on a daily ration, the optimal prey stages for CVI females, CII-IV and CI-II are NI-VI, NI-IV and NI-II respectively. Under average, natural prey density (10 nauplii l-1), S.tenellus can achieve only a small fraction (max. 9%) of the daily minimum food requirement by cannibalistic feeding. However, the impact of cannibalism on naupliar survivorship can be significant. When adult females occur at a density of 10 l-1, the mortality due to cannibalism attains 99.2% during the naupliar stages.