Distribution and life cycle of Calanus chilensis and Centropages brachiatus (Copepoda) in chilean coastal waters: A GIS approach

Abstract

Calanus chilensis and Centropages brachiatus are 2 of the most abundant species of copepods (Crustacea) off the Chilean coast. However, knowledge of their life cycle and distribution is fragmentary. We have analysed the distribution of both species in Chilean coastal waters by means of a Geographic Information System (ARC/INFO). We studied vertically integrated (0 to 100 m) zooplankton samples and ancillary physical oceanographic data collected during 1989 by the Instituto de Fomento Pesquero, Chile. Point estimates of abundance and physical data were transformed to a grid format in ARC/INFO. We show that both species are abundant within 10 km from shore, and that high abundances further offshore may be interpreted as the result of advection. We also show that both species remain year-round in the upper water column with no evidence of seasonal vertical migration. We then discuss potential life cycle mechanisms that might explain their dominance in the coastal area of the Humboldt Current ecosystem.