Deepwater Trawl and Longline Surveys in 1995

Abstract

Two surveys were carried out in 1995 as part of the continuing deep water fish research programme at the Fisheries Research Centre. The trawl survey fished areas on the eastern slopes of the Rockall Trough and on two seamounts of the mid-Atlantic ridge approximately 300 miles north of the Azores. The deep water longline trip was the first such survey carried out by the Fisheries Research Centre and concentrated on previously fished grounds in the Rockall Trough and on new areas along the slope of the Porcupine Bank. Both surveys were carried out in conjunction with an Bord Iascaigh Mhara (BIM) and the objective was to locate commercial quantities of deep water fish and to obtain samples for biological analyses. The trawl survey was conducted on a chartered fishing vessel using a commercial otter trawl, fitted with a small mesh cod-end liner. Twenty-six trawling operations were carried out in the depth range 750m-1,400m, of which 21 produced fish catches. Longlines were set between 542m and 1,521m and only one line was lost. Thirteen chondricthian and 38 species of teleost fish were recorded from the catches. The most abundant species in the catches were Portuguese shark, roundnose grenadier, black scabbard, Baird's smoothhead, blue ling and orange roughy. Length, weight, sex, maturity and catch data together with samples of otoliths and gonads were collected. Discards were monitored from both fishing methods. In comparison with the trawl, longline catches produced larger specimens of fewer species which were more dominated by sharks. Overall catch rates for the longlines were similar to Norwegian data for the Rockall area. Trawl catch rates showed a decrease since the last Irish survey in this area in 1993.