MEPS 334:255-262 (2007)  -  doi:10.3354/meps334255

ABSTRACT: 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, A₁₅) and at 20 mm (A₂₀), and the mortality coefficient during the post-recruit period (M, d^–1) were estimated for each year using the larval production method. The A₁₅ varied by a factor of 24 during the 11 yr period, and its variability had a significant effect on G, M, A₂₀, 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 A₂₀ were high when recruitment was successful. A lower coefficient of variation (%) was observed in A₂₀ (25.0) than in A₁₅ (33.5) for the 11 yr. A significant effect of A₁₅ 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.

KEY WORDS: Fish early life stages · Density-dependence · Survival · Estuarine turbidity maximum · Ariake Bay