The Impact of Fishing on Populations of Deep-water Chondrichthyan Fishes of the Northeast Atlantic
The fishing operations of a reference fleet of French commercial deep-water bottom trawlers from Lorient operating to the west of the British Isles have been described between 1999 and 2001, and their subsequent impact on several species of deep-water chondrichthyans from the area were assessed. Landings from a three-year market sampling programme showed that the deep-water fishery is highly seasonal in nature operating at greater depths in the summer months. The depth fished by vessels is primarily related to the targeted species of the fishery. Biological data from research cruises and discard observer trips have indicated that most chondrichthyan species in this study exhibit strict baythymetric distributions. The quantity and species of chondrichthyans caught as bycatch or discarded from the fishery are therefore dependent on which targeted species is caught and at what depth, and these factors can vary considerably over a limited depth range. Data collected on the reproductive biology of these species have shown that, in most instances, deep-water chondrichthyans have extremely low reproductive rates with low fecundities, slow growth and that they mature at large sizes, suggesting that they are susceptible to overfishing. A limited analysis conducted in ICES Divison VIa between pre- and post-fishery research cruises showed a decrease in catch rates for Centroscymnus coelolepis, Centrophorus squamosus and Chimaera monstrosa by decade and gear type, suggesting that these species may be some of the most vulnerable deep-water chondrichthyans when faced with intensive commercial fishing. Nevertheless data used in multivariate models were fragmentary and unbalanced in nature, and therefore results should be treated with caution. More species-specific fisheries and biological data are required in the northeast Atlantic to provide accurate management programs for deepwater chondrichthyans.
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