SPATIAL AND TEMPORAL PATTERNS OF JUVENILE STONE FLOUNDER KAREIUS-BICOLORATUS GROWTH-RATES DURING AND AFTER SETTLEMENT

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 Kareius bicoloratus is a temperate Nor th Pacific flatfish species characterized by large recruitment variabi lity and an estuarine-dependent juvenile stage. Post-larvae settle fro m 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 temp erature and feeding rates, at conditions common during settlement (8 d egrees C) and post-settlement (12 degrees C). The relationship between RNA:DNA ratio and growth rate was developed in the laboratory, and wa s used to measure in situ growth rates of juveniles from 5 different h abitats during settlement (March) and after (April). Juvenile stone fl ounder in the laboratory grew relatively quickly feeding ad libitum at 8 degrees C (4.1% body weight d(-1)) and 12 degrees C (7.0% bw d(-1)) , but growth rate was very sensitive to changes in feeding rate at bot h temperatures. Growth rate of starved juveniles was not significantly different between 8 and 12 degrees C and averaged -1.3% bw d(-1). RNA :DNA ratios were good predictors of growth rate (R(2) = 0.88), with te mperature as a covariate. In situ growth rates at all 5 stations (1 es tuary, 1 seagrass bed, and 3 deeper inshore settlement areas) were hig her in April than in March. In situ growth rates were highest during b oth months at the low-salinity estuarine station where fish had highes t gut fullnesses. Growth rates were also high at a deeper inshore stat ion near a sewage treatment outfall characterized by higher prey abund ances than those typically found in open water areas of Sendai Bay, Ja pan. Growth rates were consistently lowest at the vegetated (Zostera s pp, bed) habitat, although retention in this habitat between March and April was high. Spatial differences in sediment grain size and prey a bundances may be the primary factors responsible for the large variabi lity in habitat-specific growth rates. Temperature-corrected compariso ns of growth Limitation suggest that discrete habitats maintain their relative values as nursery grounds over time, although the magnitude o f growth limitation was much greater during settlement (March) than po st-settlement (April).