MEPS 171:247-259 (1998)  -  doi:10.3354/meps171247

Fish community structure and depth-related trends on the continental slope of the Balearic Islands (Algerian basin, western Mediterranean)

Joan Moranta1,*, Constantí Stefanescu2, Enric Massutí3, Beatriz Morales-Nin1, Domingo Lloris4

1CSIC-UIB, Institut Mediterrani d'Estudis Avançats, Campus Universitari, E-07071 Palma de Mallorca, Spain
2Can Liro, E-08458 Sant Pere de Vilamajor, Spain
3IEO, Centre Oceanogràfic de les Balears, Moll de Ponent s/n, PO Box 291, E-07080 Palma de Mallorca, Spain
4CSIC, Institut de Ciències del Mar, Passeig Joan de Borbó s/n, E-08039 Barcelona, Spain

ABSTRACT: A total of 13026 fishes belonging to 82 species and 43 families were collected in a continuous transect between depths of 200 and 1800 m south of the Balearic Islands (Algerian basin, western Mediterranean). The analysis of 32 bottom trawls showed the existence of 4 groups associated with the upper slope (groups 1 and 2, from 200 to 400 and 400 to 800 m, respectively), middle slope (group 3, from 800 to 1400 m) and lower slope (group 4, below a depth of 1400 m). The differences in the mean values of the ecological parameters species richness, abundance, biomass and mean fish weight were also indicative of distinctive characteristics between these fish assemblages. Species richness decreased significantly with depth. The highest values of diversity corresponded to the samples from group 2. Biomass did not show any specific trend throughout the whole bathymetric range. Mean fish weight show 2 different trends along the continental slope: a bigger-deeper phenomenon at the upper 1000 to 1200 m depth, and a smaller-deeper phenomenon below this depth. Our results are compared with those obtained in the north Atlantic basin and in the western Mediterranean (Balearic basin), and the main factors affecting these deep-sea fish assemblages are discussed.

KEY WORDS: Deep sea · Demersal ichthyofauna · Bathymetric distribution · Western Mediterranean

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