Side-effects of electrotrawling: Exploring the safe operating space forDover sole (Solea solea L.) and Atlantic cod (Gadus morhua L.)

tElectrotrawling is currently the most promising alternative for conventional beam trawls targeting soleand shrimp, meeting both the fisherman’s aspirations and the need for more environmentally friendlyfishing techniques. Before electrotrawling can be further developed and implemented on a wider scale,more information is needed about the effects of electrical pulses on marine organisms. Adult Dover sole(Solea solea L.) and Atlantic cod (Gadus morhua L.) were used in the present study as model species forflatfish and roundfish, respectively. These animals were exposed to homogeneously distributed electri-cal fields with varying values of the following parameters: frequency (5–200 Hz), electrical field strength(100–200 V/m), pulse polarity, pulse shape, pulse duration (0.25–1 ms) and exposure time (1–5 s). Thegoal was to determine the range of pulse parameters which can be regarded as safe and thereby alsoto evaluate the effect of the pulses already being used in commercial electrotrawls. Fish behaviour dur-ing and shortly after exposure, 14-days post exposure mortality rates, as well as gross and histologicalexamination were used to evaluate possible effects. During exposure, both species showed an escaperesponse below a frequency of 20 Hz and a cramp reaction above 40 Hz. These reactions were immedi-ately followed by post-exposure escape behaviour and at high electrical loads cod showed tonic-clonicepileptiform seizures. No mortality was observed and histological examination did not reveal any abnor-malities, except for one cod showing a spinal injury. These data reveal the absence of irreversible lesionsin sole as a direct consequence of exposure to electric pulses administered in the laboratory, while incod, more research is needed to assess cod’s vulnerability for spinal injuries when exposed to the cramppulses.

Publication year:2016

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