Preliminary results of investigations on escapement of fish under the fishing line of a Norwegian sampling trawl

The Institute of Marine Research, Bergen, has carried out combined bottom trawl and acoustic surveys for cod and haddock in the Barents Sea and the Svalbard areas since 1981. These investigations have clearly demonstrated that the currently applied survey methods in these areas underestimate the young age groups of cod considerably. One explanation may be a reduced gear efficiency for the smallest fish. This paper describes the results of experiments with small bags under the trawl, designed to collect fish that escape under the trawl. Considerable catches of different species were obtained in the small bags. A comparison between trawl and bag catches revealed a strongly length dependent escapement of cod and haddock under the trawl. The results explain to some extent the underestimation of young cod