Habitat use of shrimps in the intertidal and shallow subtidal seagrass beds of the tropical Banc d’Arguin, Mauritania

The Banc d’Arguin in Mauritania is an area characterised by shallow waters and tidal flats with extensive seagrass beds. The aim of this study was to determine the role of the Banc d’Arguin tidal flats as a habitat and a nursery for shrimps. Shrimps were sampled in the Baie d’Aouatif in the intertidal (ponds, Zostera noltii seagrass beds and bare sediment) with a push net during high and low tide, a beam trawl during high tide and in the subtidal (Cymodocea nodosa and Zostera noltii seagrass beds) with a beam trawl during low and high tide from January to March 2002. In total, eleven shrimp species (9349 individuals) were found, the most abundant of which were Palaemon elegans, Hippolyte longirostris, H. inermis (in subtidal) and Peneaus spp., whereas Athanas nitescens, Leander tenuicornis, Palaemon adspersus, Pontophilus fasciatus, Sicyonia carinata and Processa edulis subsp. crassipes were less abundant. At high tide in the intertidal all species were mainly found in sheltered areas (ponds and seagrass) rather than in unvegetated habitats. Mark-recapture experiments showed that shrimps migrate between intertidal ponds during high tide. Densities in the subtidal were similar during high and low tide, suggesting that there is no substantial tidal migration to and from the tidal flats for any of the species. Two subtidal shrimp species seemed to prefer Cymodocea nodosa beds. A large fraction of the individuals of five shrimp species carried eggs. Ten of the eleven species caught were also found as juveniles. The results of this study, and earlier studies, indicate that many shrimp species reproduce in or near the tidal-flat area of the Banc d’Arguin. Some shrimp species, notably Penaeus kerathurus and P. notialis, are likely to use the area as a nursery, migrating offshore as adults. This suggests that the Banc d’Arguin is an important resource for commercial fishery. D 2005 Elsevier B.V. All rights reserved.