The variation in species composition of continental slope fishes as determined by the catches of different trawls towed either on single or paired warps was analysed by Detrended Correspondence Analysis (DCA). The catches of two trawls, a semi-balloon trawl (OTSB) and a Granton trawl (GT) were very similar when towed on paired warps. Significant differences were found between the catches of the OTSB trawl towed on single and paired warps. The DCA effectively provided information on the important gradients, e.g. depth, trawl type, and indicated which species were most abundant in the different depth zones and trawl types. Detailed accounts of the abundance and biomass of different species by trawl type and depth zone are given and the observed pattern of distribution discussed.

No abstract

Fishery surveys of the continental slope to the west of the British Isles have shown quite marked differences between areas in both the proportion and abundance of marketable or potentially marketable species. In general, the northern slopes lying to the west of Scotland were considered to have a greater potential for exploitation than the southern slopes off Ireland.Subsequent detailed studies of a northern (Rockall Trough) and a southern slope area (Porcupine Seabight) sampled the demersal fish fauna using a Granton trawl fished on paired warps to depths of 1200 m, aiid a semi-balloon trawl fished on a single warp to depths of about 3000 m. The Granton trawl catches differed significantly between the two areas, especially at the greatest depths fished. The semi-balloon trawl catches did not differ between the areas. This slower trawl was poor at catching large, mobile species and efficient in the capture of the deep-water eel Synuphobranchus kaupi. This eel was numerically dominant over the mid to lower slopc and probably accounts for much of the similarity between areas at these depths. $~ 1996 The Fnherizs Society of the Britkh I4es

No abstract

Most deep-water fish species are long-lived, slow growing and have low reproductive capacity. These stocks are highly vulnerable to exploitation and can be rapidly depleted with recovery being very slow, often taking decades. In the Northeast Atlantic, a diversity of deep-water fisheries exists for a variety of finfish and shellfish species. The major characteristics of these fisheries are described and the available fisheries, biological and life history data are reviewed. Surplus production and DeLury models are the principal methods currently used in assessing the stocks, although agebased methods, stock reduction models and life history models are likely to be used once sufficient biological data become available. Most of the deep-water fisheries in the Northeast Atlantic have been completely unregulated; the latest stock assessments indicate that nearly all exploited deepwater species are being harvested "outside safe biological limits" and that immediate reductions in catches are needed to avoid stock depletion. Various approaches for managing deep-water fisheries resources are discussed, including the need to harmonize conservation and enforcement measures across management jurisdictions for straddling stocks.