Internal injuries in marine fishes caught in beam trawls using electrical versus mechanical stimulations

To improve the ecological and economic sustainability in the Dutch beam trawl fishery, tickler chains were replaced by electrical pulse stimulation to drive common sole (Solea solea) out of the seabed. Because electrical stimulation may cause internal injuries, we quantified this risk by sampling fish species from commercial beam trawlers and recording spinal injuries and haemorrhages from X-radiographs and autopsy. To distinguish mechanically-induced and electrical-pulse-induced injuries, we compared injuries in ten species sampled from pulse (PUL) and tickler-chain (TCK) trawlers and four species sampled from PUL trawlers with the stimulus switched on or off. Co-occurrence of a major spinal injury and major haemorrhage at the same location was only observed in PUL samples, and were frequently (40%) observed in Atlantic cod (Gadus morhua) and in low numbers (0-2%) in whiting (Merlangius merlangus), grey gurnard (Eutrigla gurnardus), and greater sandeel (Hyperoplus lanceolatus), but not in flatfishes and other species. In cod, injury occurrence correlated with fish length, with lower probabilities for small fish. Major spinal injury or major haemorrhage occurrence in PUL (range: <1-16%) was lower than in TCK (range: <1-42%) in eight of the ten species studied. Population level consequences of pulse-induced injuries are considered negligible.

Automated summary

To improve sustainability in the Dutch beam trawl fishery, electrical pulse stimulation was used to drive common sole out of the seabed. The risk of internal injuries caused by electrical stimulation was quantified through sampling and examination of fish species. Results showed that electric pulse-induced injuries were only observed in certain species, and the occurrence was generally lower than injuries caused by conventional tickler chains.