Abstract
AbstractPulse trawling is the most promising alternative to conventional beam trawls targeting Sole Solea solea (also known as Solea vulgaris), but due to the electric fields created by electrotrawls spinal injuries are reported in gadoid round fishes such as Atlantic Cod Gadus morhua. This study aimed to investigate the variability in the occurrence of electric‐induced spinal injuries in cod. Four groups of cod, each originating from a different wild or farmed stock, were exposed to the pulses used by electrotrawls targeting Sole. Effects were analyzed based on behavior, mortality, and lesions up to 14 d after exposure, and morphological characteristics such as size, somatic weight, muscularity, the number of vertebral bodies, and the vertebral mineral contents of animals were compared among different cohorts. Second, the influence of factors such as water temperature, electrode diameter, and pulse type and amplitude were tested. Electrode diameter and pulse amplitude showed a positive correlation with the intensity of the fish's reaction. However, the present experiments confirmed that cod also show variable vulnerability, with injury rates ranging from 0% to 70% after (almost) identical exposures near the electrode. This indicates that these injuries are not only determined by the pulse parameter settings but also by subtle, fish‐specific factors. Although the absence of a sensitive group of cod did not enable the elucidation of the conclusive factor, the effect of physiological and morphological factors such as intervertebral ligaments and rearing conditions during early life merit further attention in future research.Received September 3, 2015; accepted March 16, 2016
Highlights
Studies investigating the side effects of these electric pulses have revealed varying results for different marine species
Pulse trawling is the most promising alternative to conventional beam trawls targeting Sole Solea solea, but due to the electric fields created by electrotrawls spinal injuries are reported in gadoid round fishes such as Atlantic Cod Gadus morhua
Effects were analyzed based on behavior, mortality, and lesions up to 14 d after exposure, and morphological characteristics such as size, somatic weight, muscularity, the number of vertebral bodies, and the vertebral mineral contents of animals were compared among different cohorts
Summary
Studies investigating the side effects of these electric pulses have revealed varying results for different marine species. Exposure of invertebrates (Soetaert et al 2014), Sole (Soetaert et al 2016), and European Seabass Dicentrarchus labrax ( known as European Bass Morone labrax; Soetaert 2015) to the electric pulses used in the field did not elicit mortality or lesions Gadoid roundfish such as Whiting ( known as European Whiting) Merlangius merlangus and Atlantic Cod Gadus morhua, on the other hand, displayed spinal injuries (De Haan et al 2011; van Marlen et al 2014; Soetaert et al 2016), albeit with different levels of severity in terms of the number of animals affected. These environmental factors are variable in electrotrawls targeting Sole and may provide better insight into how they may result in different injury rates in cod caught by commercial electrotrawls
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