Short-term temporal variability in fish community structure at two western Mediterranean slope locations

摘要: Short-term temporal variability in deep-sea demersal fish assemblages is described for two slope areas characterised by different oceanographic conditions, which are situated north (Balearic sub-basin, BsB) and south (Algerian AsB) of the Balearic Islands (western Mediterranean). A total 75 hauls were analysed from six bottom trawl surveys carried out sub-basins. At BsB, designed sampling habitats during April 1991, December March 1992 July 1992: (i) a submarine canyon at depth around 450 m, (ii) upper 600–650 (iii) middle 1200 m. AsB, October 1996 May 1998, along continuous transect on upper, lower slope. The taxonomic composition, ecological parameters (number species, abundance biomass) biomass spectra assemblages, as well length frequency distribution main compared seasons bathymetric ranges. Forty-four species captured BsB 38 AsB. Helicolenus dactylopterus Trachyrinchus scabrus more abundant Hoplostethus mediterraneus, Galeus melastomus Centroscymnus coelolepis Depth was determinant factor all analyses. Species-specific densities (abundance showed significant differences between surveys, strata their interaction BsB. However, survey its with depth, not We also found relation to season three tested but only Biomass large slight between-survey differences, mainly occurred distributions single presented short-term variations, due varying presence larger proportion small or individuals. Depth, geographic area time factors determining composition structure assemblages. effects variations observed both replacement size some dominant subdominant throughout year. variation sub-basins might be related productivity transport benthos.