Quantitative mapping of effective habitats for the White grouper Epinephelus aeneus (Geoffroy Saint–Hilaire, 1817) in North West Africa

Abstract

Within the Mauritania–Senegal maritime zone, we have identified and mapped habitats of the white grouper (Epinephelus aeneus). To this end, data collected since the 1980s through scientific sampling surveys along the coastline and on the continental shelf in the study zone have been analysed. On the basis of data collected in shallow coastal and estuarine environments, it has been shown that only the juvenile fraction of the E. aeneus population lives in the diverse habitats (mangroves, sea grass beds, salt marshes, etc.) of both the Banc d’Arguin and the estuaries. On the continental slope, habitat suitability of both juvenile and adult was modelled, using descriptors relating to environment (bathymetry, sediment) and landscape (proximity of estuaries and the Banc d’Arguin). Bathymetry is a major factor driving these distribution patterns, while other environmental descriptors also have significant influence, though to a lesser degree: juveniles of E. Aeneus live in nearshore zones and their density is higher near the Banc d’Arguin and the estuaries, unlike the adult populations found further offshore. The density of both populations has varied over time, falling significantly in 1990, and partly recovering since 2010. These habitat maps tell us the importance of the coastal fringe as essential habitat for juvenile E. aeneus and the usefulness of space-based management measures to enhance the population and allow for sustainable fishing exploitation.