Dauer:   13. bis 26. September 2018

Fahrtgebiet:   Nordsee

Zweck der Reise:  Developping grid technologies applied to brown shrimp selectivity

The brown shrimp (Crangon crangon) beam-trawl fishery supports an international fleet of approximately 560 vessels, producing yearly revenues of up to 100 million €. From the socio-economical point of view, this is one of the most important fisheries in the North Sea, but, surprisingly, it is also one of the lesser regulated fisheries in European waters. In 2015, brown shrimp producer organizations initiated a certification process of the fishery by the Marine Stewardship Council (MSC). One of the key aspects for successful certification was the need to find out alternative gear technologies to improve exploitation patterns of brown shrimp. The little information available regarding the selectivity of commercial gears motivated the German project CRANNET (2013 – 2015). Modeling results show that an increase in mesh opening from the currently used mean of the fleet (20-22 mm) lead to a larger yield, population biomass and egg production after a short-term decrease (assuming current status of the fishery and predator abundance).

Predictions from CRANNET also showed that sharpening the size selection of codends will increase the biomass and economical revenues for the fishermen and hence, the sustainability of the fishery. This theoretical-based advice motivated one of the research topics of the cruise 739, searching for selection devices to supplement codend selectivity on brown shrimp. The cruise was planned in partnership of researchers from the Thünen Institute, Wageningen Marine Research Institute and the Fishing Industry represented by the Dutch company Visserijbedrijf Van Eekelen. The later partner designed and constructed two innovative grid concepts as potential technical solutions to address the research topic. The experimental fishing combining standard beam trawls with the grid systems yielded promising results.

Based on the promising results obtained during the cruise 739, we identified the need of improving contact probability, enabling larger fractions of shrimp being subjected to the size selection of the grid.

The main aim of the current cruise 753 is to further develop grid technologies applied to brown shrimp selectivity. It is of particular interest to find design strategies to make the selectivity of the grid available for the majority of shrimp individuals entering in the gear. A total of five different experiments are planned to address this research topic.