Development of new concepts for escape windows to minimise cod catches in Norway lobster fisheries

Abstract

Gear selectivity with regard to cod ( Gadus morhua) needs to be improved in the Kattegat and Skagerrak Norway lobster ( Nephrops norvegicus) fishery. One way to achieve this goal is to improve the selectivity of an escape window (henceforth window) in the gear. Our gear development focused particularly on moving the window further back, gaining more stability in the codend to avoid loss of Norway lobster through the window, making a relatively narrow section where the window is located, and testing larger mesh sizes in the window. We designed a four-panel sorting section—the sorting box—where a 300 mm window is placed at the top section at about 3–6 m from the codline. Acoustic release technology was used to avoid catch loss during gear retrieval. Sea trials were conducted in the Skagerrak and Kattegat from a commercial trawler. The sorting box yielded a high reduction of the cod catch, but no improvement was observed for cod that came into contact with the window after reducing the distance from the window to the codline. The sorting box also showed a high reduction of flatfish and other roundfish species. The retention of Norway lobster above minimum landing size in the sorting box was higher compared to a general selection model.