MEPS 297:245-257 (2005)  -  doi:10.3354/meps297245

Large spatial scale variation of demersal fish assemblage structure on the continental shelf of the NW Mediterranean Sea

Jean-Claude Gaertner1,*, Jacques A. Bertrand2, Luis Gil de Sola3, Jean-Pierre Durbec1, Eduardo Ferrandis4, Arnauld Souplet5

1Centre d’Océanologie de Marseille, LMGEM, UMR CNRS 6117, Rue de la batterie des Lions, 13007 Marseille, France
2IFREMER, Laboratoire Ecologie Halieutique, Rue de l’Ile d’Yeu, BP 21105, 44311 Nantes Cedex 03, France
3Centro Oceanográphico de Málaga (I.E.O.), Puerto pesquero s/n, 29640 Fuengirola (Málaga), Spain
4University of Alicante, 03080 Alicante, Spain
5IFREMER, Laboratoire Ressources Halieutiques, Bv Jean Monnet, BP 171, 34203 Sète, France

ABSTRACT: The spatial structure of demersal fish assemblages on the continental shelf of the NW Mediterranean Sea was examined on a large scale between the Straits of Gibraltar and the Gulf of Lions. In contrast to its predominant role in the spatial distribution of species composition, described worldwide, it seems depth has only a limited effect on the distribution patterns of the total abundance and diversity of demersal fishes. In addition, evidence is provided for the division of the whole study area into 3 geographical fish assemblages. The influence of Atlantic inputs and the semi-permanent Almería–Oran hydrographic front play a key role in defining the Alboran Sea as a specific fish fauna area. Moreover, the clear differentiation between 2 distinct assemblages in the Gulf of Lions and the Catalan Sea could be partly linked to the North Balearic front. These results contribute to the current debate on the definition of spatial units for the purpose of demersal fisheries management. They also stress the complexity of developing an ecosystem approach which deals simultaneously with species composition and biodiversity aspects of ecosystems management.


KEY WORDS: Demersal fishes · Assemblage structure · Species diversity · Management units · Mediterranean Sea


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