Environmental constraints and pelagic fisheries in upwelling areas: the Peruvian puzzle

Abstract

Pelagic fish catch statistics are used as surrogates to evaluate the potential fish productivity in upwelling ecosystems. A comparison between 10 upwelling areas of the world shows that the Peruvian ecosystem is three- to ten-fold more productive than the others. The size of the ecosystem, estimated by the surface of the continental shelf, does not by itself explain the observed disparity. Upwelling systems are characterized by different combinations of two different environmental variables: the upwelling intensity and the mixing generated by the wind. Using generalized additive models, an exploratory analysis is performed in order to identify the environmental conditions that maximize the total pelagic fish catch productivity (mainly sardine, sardinella and anchovy). The analyses consider fish catch as the dependent variable and the two environmental factors as the independent variables. Optimal environmental conditions appear to be a combination of: a high upwelling index (∼ 1.2 m³·s⁻¹m⁻¹) and moderate wind-mixing (∼250 m³·sm⁻³). The Peruvian ecosystem is the only upwelling system that has these characteristics, making it unique and singularly productive. These empirical results stress the importance of considering a combination of environmental factors when explaining pelagic fish productivity in upwelling systems.