West African Marine Ecosystems: models and fisheries impacts

Maria Lourdes D. Palomares and Daniel Pauly. 2004. West African Marine Ecosystems: models and fisheries impacts

West African fisheries are under tremendous pressure, some of this due to the increasing local demand for fish, and the growth of locally based industrial and artisanal fisheries. However, the main reason for the much depleted state of West African fisheries resources lies in the presence, along the West African coast, of a huge array of Distant Water fleets from Western and Eastern Europe, and from East Asia. And every few years, new 'access agreements' are signed that increase this external pressure, not to mention numerous cases of illegal fishing by a variety of countries.

Evaluations of the effects of the resulting fishing effort on West African resources have been rare so far, and widely scattered, as they were mainly dealing with isolated, local stocks. Broad-based studies, on the other hand, have been entirely lacking. This report begins to fill this gap in that it covers much of the West African coast. However, the focus has been on one region (Northwest Africa), for which a synthesis, i.e., a documentation of long-term biomass declines is presented.

This report focuses on descriptions of the methods and data used in this synthesis, i.e., in the construction of quantitative food web ('Ecopath') models of the ecosystems of the Northwest African subregion (Mauritania, Cape Verde, Senegal, The Gambia, Guinea-Bissau, Guinea and Sierra Leone) for contrasting periods (usually 1960 vs. 2000). Following a training course/workshop given in Dakar, Senegal, on February 9-23, 2001, the bulk of these models were constructed during a workshop held, also in Dakar, on August 10-18, 2001, and attended by participants representing the countries in question, all members of the European Union funded project known as 'Système d'Information et d'Analyse des Pêches' (SIAP; 'Fisheries Information and Analysis System', or FIAS in English). These models were subsequently refined in extensive collaboration among the editors and the authors, which culminated in a third workshop jointly organized by the Sea Around Us and SIAP projects, held in January 2002 at the Fisheries Centre, University of British Columbia, Vancouver, and attended by three members of the SIAP project, representing Mauritania¹ , Senegal and The Gambia. The food web models resulting from this process were complemented by models initiated by members of the Sea Around Us project, for Sierra Leone, Guinea and the Central Atlantic.

This first-ever coverage of the entire Northwest African subregion with ecosystem models, mostly pairs covering two different periods in the same country, allowed the creation of regional biomass maps for 1960 and 2000, illustrating the massive decline of the abundance of larger fishes along the West African coast. This, we assume, should impact on negotiations about access by Distant Water fleets.

The assistance provided in the preparation and actual realization of the workshops by the Director and staff of the Centre de Recherches Océanographiques de Dakar-Thiaroye (CRODT) is gratefully acknowledged, as is the readiness of various research institutions (CNSHB, Guinea; IEO, Spain; and IPIMAR, Portugal) to provide funding from their institutional budget for the participation of additional researchers in the workshops. Moctar Bâ, Director of the Coordination Unit of the SIAP project, is thanked for his untiring efforts to promote the goals and objectives of the SIAP project in the region, thus rallying the necessary support for its successful implementation. Dr. Michael Vakily, Coordinator of the SIAP project, must also be thanked for his untiring support of the work summarized in these pages. The Pew Charitable Trusts, Philadelphia, are also thanked for their support of the Sea Around Us Project.

Daniel Pauly
December 2004

¹The printed version of this report failed to include a paper describing the Mauritanian ecosystem in 1987 and 1998, included in this online version.