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    Estimating the biodiversity and distribution of the northern part of the Kerguelen Islands slope, shelf and shelf-break for ecoregionalisation: benthos and demersal fish

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    Número de documento:
    N. Améziane, M. Eléaume, P. Pruvost, G. Duhamel and Kerguelen group (France)

    More than 30 expeditions have surveyed the Kerguelen Plateau over the last 80 years. However, few of them have collected benthic organisms. Between 1961 and 1970, numerous surveys were initiated by Arnaud, Délepine, Hureau and Rannou. Sampling was done mainly close to the coast, and in limited areas. However, they collected numerous specimens and led to a first estimate of the local biological diversity. The richest cruises for the quantity of benthos collected are MD03 and MD04 (1974 and 1975 respectively) on the research vessel “Marion Dufresne”. The purpose of these cruises was to obtain quantitative and qualitative data on benthos and demersal fishes. The majority of the specimens have already been studied, although a number of them are still to be sorted and studied.

    In 1987 and 1988, the French-Soviet SKALP surveys allowed identifying fish species over the continental shelf including fish larvae. Coastal studies were carried out during the 1990’s on fish larvae, juveniles and adults (Koubbi et al., 2001). More recently, the POKER I survey (2006), for demersal fish, POKER II (2010) for benthos and demersal fish, collected a large number of specimens on the Kerguelen island shelf, with 409 operations at depths ranging from 100 to 1000 m. The aim of SKALP and POKER was to investigate the abundance, biomass and distribution of fish, including fish species on the Kerguelen Islands shelf, surrounding banks and upper deep-sea stratum. POKER II allowed to estimate the biodiversity and the distribution of benthos. Additional data over the shelf are provided by commercial fishing boats.

    The ichthyofauna of the Kerguelen Plateau is now well-known with 23 species occurring from the coastal area to the slope of the shelf (and surrounding banks), 32 deep-sea species and 57 species from the pelagic layers (epi-, meso- and bathypelagic) (Duhamel et al., 2005). Fish larvae distribution showed that there is an island mass effect allowing retention of notothenioid larvae over the shelf (Koubbi et al., 1991 and 2009). Segregation of early life stages was found to follow the scheme of Harden-Jones for some of the demersal species (Koubbi et al., 2000).

    Currently, 960 species have been recorded for benthos (Améziane et al., 2011) including 111 species of sponges, 58 species of bryozoans, 58 species of polychaetes, 51 species of pycnogonids, 219 species of crustaceans, 196 species of molluscs, 105 species of echinoderms, 93 species of ascidians and 11 species of cnidarians. All these data are available in the literature and geo-referenced.

    The French MPA project in Kerguelen will study Essential Fish Habitat, VME and patterns of diversity over the shelf including its slope and the seamounts. Essential Fish Habitat will be determined with delimiting spawning grounds, areas of distribution of larvae and nursery grounds for the most dominant species. Potential assemblages’ distributions will be determined in relation with environmental factors. For benthos, a precise inventory of species will be the first outcome. In order to define VME in the Heard-Kerguelen area, the ascidans, sponges and stalked crinoids, all recognised key taxa, will be analyzed in detail. The benthic communities will be described and used in habitat description and modelling.