Importancia de diferentes taxa de copepodos en la dieta de los adultos de anchoita (Engraulis anchoita) bonaerense durante la época reproductiva
Engraulis anchoita is the most abundant and widespread ichthic species in the SW Atlantic. Two populations of the species occur in the Argentine Sea, a northern one or Bonaerense (34 degree -41 degree S)and a southern one or Patagonian (41 degree -47 degree S). The former performs an annual migratory cycle which includes the concentration in the northern area in winter, the distribution in coastal waters off Buenos Aires prov. during spring spawning period and the concentration in the shelf feeding ground in summer. In this work the feeding habits of the northern population were studied in its spring habitat. Fish samples were obtained in 16 stations from the Buenos Aires prov. shelf, during a research cruise of the INIDEP (National Institute for Fisheries Research and Development)Anchovy Project (OB-07/04). The stomachs of 240 individuals of anchovy adults were analyzed. The repletion stomach level found was in general low. The few individuals reaching higher values were particularly located near the Rio de la Plata estuary front. The most important identified preys were copepods 1mm of total length (TL), represented mainly by calanoids followed by cyclopoids. Nevertheless the major biomass contribution was due to calanoids 1-2 mm TL followed by calanoids 1mm TL. Other important food items were appendicularians, cladocerans and fish eggs. When the distribution and number of prey observed in stomach content of anchovy were compared with the distribution and abundance of zooplankton in the field, a non selective filtration pattern was observed. Present results suggest that within the spring spawning area of northern anchovy population, the Rio de la Plata estuarine front offers the best trophic conditions for adult individuals.