Feeding Ecology of the Sand Shrimp Crangon hakodatei Rathbun (Decapoda: Crangonidae) in the East Coast of Korea

Abstract

The feeding habits of sand the shrimp Crangon hakodatei were investigated in the East Coast of Korea based on the analysis of 602 stomach contents, with comparison by season and size class of diet composition and prey diversity. The investigation also took account of the influence of season, sex, size and area variation in the diet composition and prey diversity. The relative degree of stomach fullness, frequency of occurrence and relative abundance were also determined. Specimens were collected monthly over a period from August 2010 to May 2011 at depths of 30 to 60 m. The diet of C. hakodatei consisted of 17 different prey categories, and belonged mainly to crustaceans (e.g. amphipods, mysids, isopods, cumaceans, decapods and copepods), molluscs (e.g. gastropods and bivalves), polychaetes, nematodes, algae and fishes. The above prey categories consisted of 89.1% of the relative abundance and 92.79% of frequency of occurrence in prey item for males. For females it consisted of 85.9 % of the relative abundance and 91.32% of the frequency of occurrence. Crustaceans were the dominant items of the diet. Molluscs, nematodes and fishes were also memorable prey items, whilst other food categories like polychaetes and algae occurred in low percentages. For small-sized shrimps (< 10 mm carapace length) amphipods and mysids consist of more than 67% of its food items in both relative abundance and frequency of occurrence. Large-sized shrimps (>10 mm CL) tended to be more dependent on amphipods more than mysids. Amphipods and mysids together constituted the dominant prey, accounting for over 50% of the diet in both percent occurrence and relative abundance. The abundance and occurrence composition of food items showed a seasonal variation. Amphipods and mysids were the predominant prey items in autumn (45%), winter (30%) and spring (40%). There was also variation according to area. With amphipods and mysids being conspicuously the predominant prey items in area 1 (40%) and area 2 (45%). Amphipods were the most dominant food item with regard to season, size class, sex or area. The females feeding behaviour differed among the seasons. In spring, decreased feeding activity, highest value of vacuity index and lowest values of stomach fullness have been shown.