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Influence of trawl type on the composition and diversity of deep benthopelagic fish and decapod assemblages off the Catalan coasts (western Mediterranean)
Joan E. Cartes, Francesc Maynou, Domènec Lloris, Luis Gil de Sola and Mariano Garcia

A series of 57 (600-750 m) and 32 (1184-1320 m) hauls were compiled to compare data from four trawl types in analyses of the species composition and diversity of deep benthopelagic fish and decapods off the Catalonian coasts (western Mediterranean). Two 1-warp trawls (OTSB-14 and MTS-25) and two 2-warp trawls (a commercial trawl [CT] and a GOC73) were used, from hauls performed between 1988 and 2007 were compiled. At 600-750 m the OTSB-14 hauls were separated in multi-dimensional scaling (MDS) from hauls performed with MTS-25, CT, and GOC73. Ordination of hauls along DIM1 of MDS was significantly correlated (Spearman’s r) with mesh size at codend, bridle length, and vertical opening of trawls. When CT and GOC73 were compared with MTS-25, the most dissimilar species were Aristeus antennatus, Galeus melastomus and Trachyrhynchus scabrus. A particular case was A. antennatus, with a significantly higher abundance in MTS-25 catches than the rest of the trawls. At 1200-1300 m the OTSB-14 and MTS-25 hauls were segregated in MDS analysis. DIM2 was correlated with the sampling period (month), indicating a temporal effect on haul composition. At 1200-300 m the main dissimilarities between OTSB-14 and MTS-25 were marked by Alepocephalus rostratus and A. antennatus (caught with MTS-25), and by Cataetyx alleni, the Notacanthidae Notacanthus bonapartei and Polyacanthonotus rissoanus, and Plesionika acanthonotus (caught with OTSB-14). As a conclusion, OTSB-14 showed a significantly higher abundance in catches than MTS-25, CT and GOC73, and a higher S (number of species) and J (equitability) than MTS-25. On the lower slope seasonality influenced trawl comparisons; however, it is likely that MTS-25, with higher vertical height than OTSB-14, caught the benthopelagic fish A. rostratus more efficiently, explaining the higher biomass from MTS-25 there. MTS-25 positively selected A. antennatus, in parallel to a negative catchability for other species.

Keywords: deep sea, trawl comparison, diversity, decapod crustaceans, fishes, Aristeus antennatus, OTSB
Contents of this volume Sci. Mar. 73(4) : 725-737 Back PDF
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