Development and testing of a separator frame in a Norway lobster Nephrops norvegicus fishery

Norway lobster Nephrops norvegicus fisheries are often characterized by high bycatch and discard rates. However, fisheries species exhibit differences in vertical behaviour that can be used to develop selective devices. We developed a separator frame that can be inserted into the forward part of a cod-end to divide it into a bottom cod-end and a top cod-end.

In the top cod-end we inserted a 3-m-long window constructed of 274-mm mesh. The separator frame was tested from a commercial vessel in the Kattegat and Skagerrak area. Small mesh net bags were used to collect the catch going through the separator frame and ending up in the bottom cod-end, the top cod-end, or penetrating the window.

The majority of Norway lobster and flatfish entered the bottom cod-end, and most gadoids entered the top cod-end. A relatively high proportion of gadoids and flatfish that entered the top cod-end penetrated the window. The separation was size dependant for some of the investigated species.