Co-location of passive gear fisheries in offshore wind farms in the German EEZ of the North Sea: A first socio-economic scoping

tMonotonous size selection curves have traditionally been sufficient to describe the size selection in theaft end of a bottom trawl. Such modelling is a good approximation when the size selective system con-sists of a single selective device. However, in some fisheries the demands for species and size selectivityhave motivated the development of selective systems in trawl fisheries that utilize more than one selec-tive device simultaneously.

An example can be found in the Swedish demersal trawl fishery targetingNorway lobster (Nephrops norvegicus), which simultaneously aims at avoiding catches of Atlantic cod(Gadhus morhua). In this fishery, the selective system consists of a Nordmøre type sorting grid followedby a size selective square mesh codend.

The size selection curve for this system has a characteristic bell-shaped curvature, which cannot be sufficiently described by a monotonous selection curve. An approachthat can handle a bell shaped curvature is to use a more flexible empirical size selection model. However,such models primarily use a curve fitting procedure, and do not allow the possibility to investigate thecontribution of the individual parts of the selection system.

Therefore, we choose to use a structural-based model that directly models the contributions of the individual selectivity devices to the overallperformance of the system. We demonstrate that this approach can appropriately describe the experi-mental size selection data for both Nephrops and cod in a system composed of a sorting grid followed bya size selective codend.

Furthermore, this approach provides a direct quantification of the selective pro-cesses of the individual parts of the system to the overall size selection in the fishing gear. In addition, wedemonstrate how this approach can provide fisheries managers with a new tool when trying to developmore sustainable fisheries through improving fishing gear size and species selectivity