A STUDY OF OPTIMUM POSITIONING OF SQUARE-MESH ESCAPE PANELS IN IRISH SEA NEPHROPS TRAWLS

The position of a square-mesh panel in a 70-mm Nephrops trawl of the t ype widely used in the Irish Sea was varied to examine the effect on c atch rates of whiting (Merlangius merlangus) of different sizes. Panel s of 75-mm mesh size and 3 m length were positioned either 1 m in fron t of the cod-end extension, conforming with United Kingdom (UK) legisl ation, or 7 m in front of the extension, conforming with Irish (IRL) l egislation. Forty-three tows of a twin Nephrops trawl were carried out from a commercial fishing vessel of the type using this gear in the I rish Sea, with different panel positions in the two nets. In a subsequ ent experiment, the twin trawl was separated into two single trawls an d 40 parallel hauls were carried out from two smaller commercial trawl ers typical of the single-rig Nephrops fleet in the Irish Sea. In each experiment, the trawls were deployed over a range of depths. Rigged a s a twin trawl, the IRL net consistently caught fewer whiting below th e minimum landing size (MLS) of 27 cm than did the UK net (mean catch rates of 72 +/- 10 and 131 +/- 14 fish per hour, respectively). Catch rates above MLS were almost identical in most hauls. In contrast, the panel position had no significant effect on catch rates of whiting of all sizes when the same nets were towed in parallel by the two smaller vessels. Possible reasons for these differences in results are discus sed. As catch rates of whiting above MLS were not affected by panel po sition in both sets of trials, it is concluded that the more forward p anel position would be most appropriate for Nephrops fisheries involvi ng both single and twin trawls. (C) 1998 Elsevier Science B.V.