THE EFFECT OF SEASONAL ANOMALIES OF SEAWATER TEMPERATURE AND SALINITYON THE FLUCTUATION IN YIELDS OF SMALL YELLOW CROAKER, PSEUDOSCIAENA-POLYACTIS, IN THE YELLOW SEA

To include the effects of environmental factors on the production of s mall yellow croaker, Pseudosciaena polyactis Bleeker, in the Yellow Se a, we applied time series analysis to the commercial catch and salinit y and temperature data for the period 1970 to 1988. Residuals from a w eighted least-squares regression of log-transformed catches against ye ar and month were calculated to remove not only seasonal factors but a lso long-term trends in catches. The residuals of mean and standard de viation (SD) of temperature and salinity were calculated and used for autocorrelation, crosscorrelation and first-order autoregression analy sis (AR(1)) using maximum likelihood. The landings showed a decreasing pattern across years with a conspicuous seasonal cycle within years. Catch residuals showed a strong positive autocorrelation and a conspic uous time-lagged cross-correlation with the residuals of mean and SD o f seawater temperature at 75 m. AR(1) revealed that positive anomalies of mean temperature were associated with positive anomalies in the pr oduction of small yellow croaker with a one year time lag. The decreas e in the residual of SD of temperature appears to be related to the hi gh production 0.5-1.0 year later. The effect of salinity was negligibl e compared with that of temperature. Therefore, the warm spawning peri od and homogeneous temperature condition of previous years for young f ish may cause the increase in the following year's yield of this fish species. When used to predict catches in 1989 and 1990, the AR(1) mode l explained 40% of the variances of the observed landings.