Maximum handling size, prey size and type selection by snakehead (Channa argus) feeding on juvenile Chinese mitten crab (Eriocheir sinensis).

摘要

Laboratory predation trials were conducted to investigate maximum handling size, prey size and type selection by small (35-37 cm in total length, L_T), medium (43-46 cm L_T) and larger (58-60 cm L_T) snakehead (Channa argus) when feeding on a wide size (9-34 mm in carapace width, C_W) range of juvenile Chinese mitten crab (Eriocheir sinensis). The maximum handling size of predator feeding on crabs monotonically increased with predator L_T and mouth gape width, G_W. Snakehead with at least 16.0 cm L_T or 27.7 mm G_W would be capability to consume the smallest size group of crabs, whereas the predator with 72.6 cm L_T or 63.4 mm G_W would be capability to consume all size groups of crabs in these trails. Prey-size selection trials showed that snakehead has a high preference to the small-sized crabs, and lower preference to the medium or large size crabs. The preference index was significantly affected by prey size and prey size x predator size interaction, however, was not affected by predator size. In prey type experiments, snakehead consumed lower proportions of juvenile crabs when fed on the crab and crucian carp than when fed on only the crab, which suggests alternative fish prey may reduce predation risk of the crab by snakehead in nature. These results could be useful for improving the fishery management and release strategies for the crab.