Temperature and massive fish deaths in southern South America

based on a compilation of data on massive fish deaths occurred in southern south america during the twentieth century, we assessed the importance of climatic variables on these phenomena. we found a strong relationship (r2 =0.68) between these massive fish deaths and the mean monthly air temperature. along the annual temperature range there is a central range (14.6° c to 20.0° c), where the probabilities that a fish community suffers massive deaths is very low. its central point (17.3° c) is very close to the mean annual value (17.2° c) of air temperature variation. we considered this agreement as corroboration at community level of pianka’s theory on physiological optima. this relationship allows to monitoring the influence of climate changes, because the environmental variation and the zones of mortality and no mortality will change with predicted changes of the mean monthly values of air temperature.