Density-dependence in post-recruit Japanese seaperch Lateolabrax japonicus in the Chikugo River, Japan

Density-dependence in feeding, growth, and mortality was evident in the post-recruit riverine period (15-20 mm in length) of Japanese seaperch Lateolabrax japonicus located within the estuarine turbidity maximum of the Chikugo River, Japan.Based on otolith microstructure analysis, the weight-specific growth coefficient (G, d -1 ) and abundance-at-age were estimated for post-recruit Japanese seaperch from 1990 to 2000.Abundance at recruitment (15 mm, A 15 ) and at 20 mm (A 20 ), and the mortality coefficient during the post-recruit period (M, d -1 ) were estimated for each year using the larval production method.The A 15 varied by a factor of 24 during the 11 yr period, and its variability had a significant effect on G, M, A 20 , and the ratio of M to G as an index of Japanese seaperch relative recruitment potential.G was low, and M, ratio of M to G, and A 20 were high when recruitment was successful.A lower coefficient of variation (%) was observed in A 20 (25.0) than in A 15 (33.5) for the 11 yr.A significant effect of A 15 was also found on the prey ingestion of the post-recruit Japanese seaperch.Mean gut fullness (gut content weight per unit body weight) was low when recruitment was successful.Density-dependent regulation through competition for prey resources operates on Japanese seaperch in the post-recruit period corresponding with the migration from Ariake Bay to the Chikugo River, a spatially restricted nursery.