Solea, 732nd cruise

Duration:       March 21 to 30, 2017

Area:    North Sea; commercial shrimp catching sites in Germany and the Netherlands

Purpose:   Investigations with the shrimp-pulse beamtrawl

The shrimp fishery is a small and regional coastal fishery. Nevertheless, it is the most important Ger-man fishery – based on the economic revenues.

The standard gears in this North Sea shrimp fishery are beamtrawls with a Bobbin-Groundrope. A standard beamtrawl (8m width) has around 36 bobbins. These bobbins have two duties: a) the bobbins guide the net over the bottom and b) they startle shrimp to jump off the bottom.

Unfortunately, the bobbins also stimulate other bottom living species, such as flatfish species. Usually, those unwanted animals are caught and discarded – a point of criticism. Another critical point is the bottom contact of the bobbins, which potentially harm the sea bottom and requires additional energy.

To reduce the number of bobbins, other ways to stimulate the shrimp have to be found – ideally only the shrimp. One option is the usage of electrical fields. Our Belgian colleagues developed the shrimp-pulse beam trawl, using a pulsed electrical field, optimized for shrimp (5 stimuli per second). This shrimp-pulse trawl was intensively studied in Germany with focus on changes on catchability. The consequences of these pulsed electrical fields on other marine organisms were investigated in Belgium and the Netherlands. So far, no negative influence on such organisms was found. Nevertheless this fishing method is discussed critically in relation to potential negative effects of electric fields (whereas, it is often not distinguished between shrimp-pulsetrawl and sole-pulsetrawl). During this cruise we want to investigate whether it is possible to efficiently catch with the shrimp-pulsetrawl using reduced pulse parameters (pulse duration and number of pulses). These experiments at sea are based on Lab-experiments, which were conducted in October 2016 in Ostende – and have shown good results.

Scientific cruise leader: