MEPS 131:49-59 (1996)  -  doi:10.3354/meps131049

Spatial and temporal differences in habitat characteristics of coastal nursery grounds can have a large impact on growth rate, survival, and subsequent recruitment of species with estuarine-dependent early life history stages. Stone flounder Kareiusbicoloratus is a temperate North Pacific flatfish species characterized by large recruitment variability and an estuarine-dependent juvenile stage. Post-larvae settle from mid-January to early April in inshore and estuarine nursery grounds, and juveniles subsequently move farther inshore using selective tidal stream transport. Laboratory studies were conducted to determine the sensitivity of juvenile stone flounder growth rates to changes in temperature and feeding rates, at conditions common during settlement (8*C) and post-settlement (12*C). The relationship between RNA:DNA ratio and growth rate was developed in the laboratory, and was used to measure insitu growth rates of juveniles from 5 different habitats during settlement (March) and after (April). Juvenile stone flounder in the laboratory grew relatively quickly feeding ad libitum at 8*C (4.1% body weight d^-1) and 12*C (7.0% bw d^-1), but growth rate was very sensitive to changes in feeding rate at both temperatures. Growth rate of starved juveniles was not significantly different between 8 and 12*C and averaged -1.3% bw d^-1. RNA:DNA ratios were good predictors of growth rate (R² = 0.88), with temperature as a covariate. Insitu growth rates at all 5 stations (1 estuary, 1 seagrass bed, and 3 deeper inshore settlement areas) were higher in April than in March. Insitu growth rates were highest during both months at the low-salinity estuarine station where fish had highest gut fullnesses. Growth rates were also high at a deeper inshore station near a sewage treatment outfall characterized by higher prey abundances than those typically found in open water areas of Sendai Bay, Japan. Growth rates were consistently lowest at the vegetated (Zostera spp. bed) habitat, although retention in this habitat between March and April was high. Spatial differences in sediment grain size and prey abundances may be the primary factors responsible for the large variability in habitat-specific growth rates. Temperature-corrected comparisons of growth limitation suggest that discrete habitats maintain their relative values as nursery grounds over time, although the magnitude of growth limitation was much greater during settlement (March) than post-settlement (April).

Stone flounder . Kareius bicoloratus . Growth . Habitat . RNA:DNA . Recruitment