Abstract

An ecotrophic model was constructed to assess energy flows in the pelagic food web off northern Chile (18°20'S - 24°00'S; from the coast to 60 nm west; encompassing 35,000 km 2) in 1989. Required input parameters were obtained from the literature and other models applied to upwelling ecosystems. The model considered 13 functional groups. Although the analysis emphasized fishery resources, it also included by-catch species from the pelagic fishery and other important groups such as phytoplankton, zooplankton, detritus, and top predators. The model was built using Ecopath with Ecosim software version 5.1. The results indicated that the total flow, an estimate of system size, was 38,674 ton·km -2·year -1. System primary production was calculated at 13,452 ton·km -2·year -1. The average trophic level of the catch in northern Chile is estimated to be 2.7, indicating that catches are sustained mainly by species from lower trophic levels, such as sardine (Sardinops sagax). The average transfer efficiency is estimated to be 9.8%, which is in the range reported for marine food webs. This ecosystem is far from maturity, has low-efficiency energy transfers, short trophic chains, and low levels of recycled matter, consistent with reports from the world's main upwelling ecosystems. © 2007 Escuela de Ciencias del Mar Pontificia Universidad Católica de Valparaíso.