Grazing patterns of copepods in the upwelling system off Peru

Abstract

The amount of food eaten by copepods of three genera (estimated from chlorophyll and pheophytin in the guts of the animals) was measured to determine the depth and also the time of day of the maximum and minimum intensity of feeding. Copepods were taken with a large volume (800 liters min −1 ) pumping system at five depths (0–85 m) and twelve sampling intervals (every 4 h) at three stations in the Peruvian upwelling system. Results indicate that Eucalanus could withstand periods of 12 h in anoxic layers, but Calanus and Centropages tended to be found in waters having more than 0.8 and 0.2 ml O 2 ·liter −1 , that in situ filtration rates could be derived which were in accord with filtration rates obtained from laboratory studies, that individuals of the three genera migrated in and out of the 5‐m surface layer when food was abundant but did not show a coherent diurnal vertical migration when food was scarce, and that the three genera maintained different feeding strategies which were amplified when food was scarce. The results are consistent with the concepts of resource allocation and separation of niches by species.