Evaluation of the impact of electro shrimp trawl fishery

Brown shrimps are caught with bottom trawls, as is the case for 90% of all demersal fish, shell and
crustacean landings in the North Sea. These demersal trawl fisheries are known to produce large
amounts of discards and to disturb the seafloor habitat of benthic organisms. This results in severe
ecosystem damage and the indirect reduction of quota in other fisheries. Furthermore fuel
consumption is high. In order to increase the sustainability of these fisheries and consider
ecological certification,technical adaptations are necessary to avoid these problems. Electric pulse
fields have proven to be the most promising option for alternative stimulation in fishing gear,
replacing the mechanical stimulation.
Since 2008 the Belgian ILVO research institute has been successfully testing their Hovercran electro
pulse trawl for brown shrimp fishery. In this device the heavy bobbin rope is replaced by light
weight electrodes creating a low-intensity electric fieldwhich selectively induces a startle response in
the shrimps. Other benthic organisms are left untouched and can escape underneath the hovering
trawl that collects the jumping shrimpswithout disturbing the seabed (Verschueren et al., 2009).
Nevertheless, the effects of suchlike electric pulse field on marine organisms are largely unknown
(Snyder, 2003). Preliminary exposure and survival experimentsindicated that the use of this low
frequency pulse has no immediate significant effects on most adult fish and invertebrate species
(Vercauteren et al., 2010). However, electro sensitive fish, like sharks and rays, and polychaete
species, which have a key role in the benthic ecosystem, were not included in these studies.
Additionally, the influence on different life stages has never before been investigated. Electrofishing
over active spawning grounds may affect survival of embryos, larvae or juveniles if exposed during
their more sensitive stages (Bohl et al., 2010). Further research to fill these gaps in knowledge
hence is crucial to revalue pulse fishing and to provide information enabling to lift the standing ban
on electric fishing in the EU.