SEASONAL SIZE VARIATION AND GROWTH OF CALANUS-CHILENSIS BRODSKY IN NORTHERN CHILE

Seasonal size variation of marine copepods has long been noted in the literature. Such variation is thought to be mostly determined by tempe rature and food availability throughout the year. Monthly samples of C alanus chilensis Brodsky, obtained at a fixed station in Bay of San Jo rge, Antofagasta, along with vertical profiles of temperature, were us ed to analyze seasonal variation of prosome length, ''structural dry w eight'' (SW) (lipid-discounted) and nutritional condition of adult fem ales, copepodites CV and CIV. Previous studies suggest that body lengt h may be more affected by temperature than food. Individual weight, on the other hand, seems to be more affected by food condition, although this weight may show a certain stability despite growing condition if lipids are discounted, i.e. SW. In this study body length of adults ' 'females'' and stage CV were negatively correlated to mean temperature of the water colunm, although length of CIV did not show such correla tion. SW and a condition index (Ci) show a seasonal pattern not associ ated with temperature. Therefore we found no support for the hypothesi s of stability of SW. However, this species appears to continuously re produce through the year, so that there is a possibility that a season al pattern of SW estimates in adult ''females'' may result from differ ences in amounts of reproductive material, even although SW might stil l remain stable in nature. Measured and estimated mean SW were plotted against stages of development resulting an exponential-like curve. Th is suggests that growth may be exponential and hence not limited by fo od conditions. However such conclusion needs to be rested by having es timates of stage durations, or the time required to reach these values of SW.