| Sumario: | Seasonal size variation of marine copepods has long been noted in the literature. Such variation is thought to be mostly determined by temperature and food availability throughout the year. Monthly samples of Calanus chilensis Brodsky, obtained at a fixed station in Bay of San Jorge, Antofagasta, along with vertical profiles of temperature, were used to analyze seasonal variation of prosome length, ''structural dry weight'' (SW) (lipid-discounted) and nutritional condition of adult females, copepodites CV and CIV. Previous studies suggest that body length 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 correlation. SW and a condition index (Ci) show a seasonal pattern not associated with temperature. Therefore we found no support for the hypothesis of stability of SW. However, this species appears to continuously reproduce through the year, so that there is a possibility that a seasonal pattern of SW estimates in adult ''females'' may result from differences in amounts of reproductive material, even although SW might still remain stable in nature. Measured and estimated mean SW were plotted against stages of development resulting an exponential-like curve. This suggests that growth may be exponential and hence not limited by food conditions. However such conclusion needs to be rested by having estimates of stage durations, or the time required to reach these values of SW.
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