Climate modulates the effects of Sardinella aurita fisheries off Northwest Africa

Abstract

The fluctuating abundance of round sardinella (Sardinella aurita) in Mauritanian waters over the past ca. 20 years can be related to environmental dynamics off Northwest Africa. Trends in the fishery are evaluated using FAO data, acoustic surveys, and catch statistics from the EU fleet (1996–2006). Remote sensing data demonstrate rising annual sea surface temperatures, up to 3 °C higher than the long-term average in 2002–2003, following a shift in ocean climate in 1995. Fish abundance and repeated expansion of the sardinella population in the past 10 years are attributed to favorable oceanographic conditions and increased recruitment success. Sardinella thrives with intense upwelling and high primary production during spring, and retention of waters over the shelf during summer and autumn. The stock of S. aurita over the Northwest African shelf oscillates with the cold–warm states of the habitat. Favorable hydrographic conditions and extended habitat has resulted in unprecedented rise of sardinella abundance in the late 1990s, which was counterbalanced by the impact of fisheries. A backshift to a cold-state ecosystem, with extensive regional upwelling and decreased sardinella habitat, would topple that balance.