No Injuries in European Sea Bass Tetanized by Pulse Stimulation Used in Electrotrawling

Abstract

Electrotrawling using electric pulse stimulation is a promising alternative to beam trawling in the brown shrimp Crangon crangon and Dover Sole Solea solea (also known as Solea vulgaris) fisheries of the North Sea. In the sole fishery, a 40-80-Hz pulse stimulation induces tetany in the muscles, which may result in injuries. Whereas no injuries have been reported in flatfish or selachian sharks and rays, electrically induced spinal injuries have been observed in gadoids such as Atlantic Cod Gadus morhua and Whiting (also known as European Whiting) Merlangius merlangus. This may indicate that fish species with a fusiform shape are more susceptible to electric pulses. Similar variation among species in electrically induced spinal injuries has been observed in freshwater electrofishing, although large variability in vulnerability has been reported among different freshwater fusiform species. Therefore, we aimed to assess the vulnerability of another, nongadoid, fusiform osteichthyan: Sea Bass Dicentrarchus labrax (also known as European Bass Morone labrax). Two length groups of Sea Bass (31.3 AE 2.2 and 42.1 AE 2.5 cm) were exposed to electric pulses as used in commercial electrotrawls targeting Sole (80 bipolar pulses per second, 2% duty cycle). Thereafter, the fish were monitored daily and then euthanized 14 d after exposure for gross, radiographic, and histologic examination. No injuries were found in fish exposed to the electrical pulses. Differences in vertebral morphology among fusiform species may result in varying vulnerabilities to electrically induced

Effect of electrical stimulation used in the pulse trawl fishery for common sole on internal injuries in sandeels

“…Minor abnormalities were observed in similar numbers in exposed and control fish and are therefore unlikely to be electrical-pulse induced. These minor abnormalities may be developmental deformations or old injuries from which the fish have recovered, and therefore are unrelated to electrical-pulse exposure (Sharber et al, 1994;Soetaert et al, 2018;Boute, 2022).…”

“…These factors may set different thresholds for inducing double-sided muscle cramps. Moreover, differences in body characteristics such as the distribution of muscle mass and number, shape, and size of vertebrae may affect the probability that pulse-induced muscle cramps lead to internal injuries (Soetaert et al, 2018;Boute, 2022). Interspecific differences in sensitivity to pulse-induced internal injuries are therefore to be expected.…”

The implications of a transition from tickler chain beam trawl to electric pulse trawl on the sustainability and ecosystem effects of the fishery for North Sea sole: an impact assessment

“…The electric field near to the electrode array, within the surrounding nets, induces muscle cramps in the fish (Soetaert et al, 2019). These muscle cramps may consequently lead to spinal injuries and haemorrhages (van Marlen et al, 2014;de Haan et al, 2016;Soetaert et al, 2016aSoetaert et al, , 2016bSoetaert et al, , 2016cSoetaert et al, , 2018. Internal injuries, however, may also be caused by an external mechanical load acting on the body of the fish.…”

“…In addition to heavy injuries, also minor deformations and abnormalities were found in the fishes. However, since these have not been related to electrical-pulse induced injuries in laboratory exposure studies (Sharber et al, 1994;Soetaert et al, 2018), we excluded these here.…”

Guidelines for defining the use of electricity in marine electrotrawling

“…These side effects result from simultaneous electrically induced muscle contractions at both sides of the fish' body, an unnatural response because mutual inhibition via interneurons in the spinal cord normally prevents simultaneous contractions of left-andright swimming muscles in fish (e.g. Uematsu, 2008;Fetcho and McLean, 2010) and mainly occurs in fusiform fish with a high number of small vertebrae such as trout and salmon species (Snyder, 2003) or Atlantic cod (Soetaert et al, 2018).…”