1Akkeshi Station, National Center for Stock Enhancement, Fisheries Research Agency, Akkeshi, Hokkaido 088-1108, 2Faculty of Marine Science, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, Japan
This study was conducted to examine the effects of prey (Artemia nauplii) density on survival, development and feeding of the horsehair crab Erimacrus isenbeckii larvae. Six levels of prey densities (0, 0.25, 0.5, 1, 2, 4 individual (ind.)/mL) were examined for their effects on survival, developmental period from hatching required to reach each larval stage, and growth of larvae. The number of prey consumed per larva per day was determined at five levels of prey densities (0.25, 0.5, 1, 2, 4 ind./mL) at the first, third and fifth zoeal stages. Survival rates increased with high prey density, and survival rates at the first crab stage were significantly higher at 2-4 ind./mL than at 0-0.5 ind./mL (P<0.05). The number of days required to reach each stage was lower as prey density levels increased, and was significantly lower at 2-4 ind./mL than at 0.25-1 ind./mL (P<0.05). Regarding growth, carapace length was longer as prey density levels increased, and carapace length at the megalopal stage was significantly longer at 2-4 ind./mL than at 0-0.5 ind./mL (P<0.05). The number of prey consumed by larvae tended to increase with high prey density; growth and zoeal feeding showed a tendency to be saturated when prey density level was 2 ind./mL. These results suggest that the optimal prey density for larval rearing of horsehair crab is at least 2 ind./mL.