1Fisheries Experimental Station, Wakayama Prefectural Reserch Center of Agriculture, Forestry and Fisheries, Kushimoto, Higashimuro, Wakayama 649-3503, 2Division of Fisheries Promotions of Fisheries Bureau of Agriculture, Forestry and Fisheries of Wakayama Prefecture, Wakayama 640-8585, Japan
Hatch dates and early growth rates of ayu Plecoglossus altivelis altivelis in the coastal waters of western Kii Peninsula from 1990 to 1997 were estimated by otolith microstructure. Mean growth rates of juvenile ayu hatched in November were significantly positively correlated with plankton biomass in January and negatively correlated with sea surface temperature (SST) in December. Hatch dates of juvenile ayu were distributed in the early spawning season in the northern coastal areas (Yuasa Bay) compared to the southern coastal areas. The mean growth rates of juvenile ayu hatched in November were higher in the northern coastal areas than the southern coastal areas. With the increase of juvenile ayu, the growth rates tend to increase in the Hidaka coastal areas. These results suggested that the stock size of juvenile ayu is associated with plankton biomass, SST and the early growth rates during the winter season in the coastal waters of western Kii Peninsula.