Relationship between daily survival rates of larval Japanese anchovy (Engraulis japonicus) and concentrations of copepod nauplii in the Seto Inland Sea, Japan

We attempted to estimate the survival rates of larval cohorts (3-15 mm in body length) of the Japanese anchovy Engraulis japonicus population in Hiuchi-nada, Seto Inland Sea, Japan, and examined the relationship to their food availability. The survival rates were directly calculated from the change in larval density during the survey. The estimated daily survival rate ranged between 0 and 89% d(-1), but increased with the increase in the mean concentration of small-sized copepod nauplii (< 100 mu m in body length) sampled at 10 m depth. When the food concentration was higher than about 5 nauplii L-1, the daily survival rate of larval anchovy reached an asymptote of approximately 89% day(-1). It might be possible to provide a framework for the forecast for larval abundance immediately prior to recruitment size (10-15 mm SL), based on larval abundance of the monitored size (3-8 mm SL) and the survival rate which is estimated from the concentration of small-sized nauplii.