The efficacy of electrical stunning of New Zealand rock lobster (Jasus edwardsii) and freshwater crayfish (Paranephrops zealandicus) using the Crustastun™

Abstract

Large numbers of decapod crustacea are farmed and harvested globally for human consumption. Growing evidence for the capacity of these animals to feel pain, and therefore to suffer, has led to increased concern for their welfare, including at slaughter. In New Zealand, decapod crustacea are protected by animal welfare legislation. There is a requirement that all farmed or commercially caught animals of these species killed for commercial purposes are first rendered insensible. The aim of this study was to evaluate the efficacy of the Crustastun™, a commercially available bench-top electrical stunner, in two commercially important New Zealand crustacean species; the rock lobster (Jasus edwardsii) and kōura (freshwater crayfish [Paranephrops zealandicus]). Animals were anaesthetised via intramuscular injection of lidocaine and instrumented to record the electrical activity of the nervous system, prior to being stunned according to the manufacturer’s instructions. Stunning efficacy was determined by analysing neural activity and observing behaviour post stunning. All ten P. zealandicus and three J. edwardsii appeared to be killed outright by the stun. Of the remaining J. edwardsii, six exhibited some degree of muscle tone and/or slow unco-ordinated movements of the limbs or mouthparts after stunning, although there was no recovery of spontaneous or evoked movements. One J. edwardsii was unable to be stunned successfully, likely due to its very large size (1.76 kg). None of the successfully stunned animals showed any evidence of return of awareness in the five minutes following stunning. It was concluded that the Crustastun™ is an acceptable method for killing P. zealandicus and for stunning all but the largest J. edwardsii.

Towards the humane slaughter of decapod crustaceans: identifying the most effective indicators of insensibility following electrical stunning

“…Fregin and Bickmeyer (2016) used implanted electrodes in the abdominal nerve cord of the American lobster Homarus americanus and the crayfish Astacus leptodactylus, and analysed the signals using Fourier analysis (FFT). More recently, Kells et al (2023) recorded global neural activity from superficially placed electrodes placed anteriorly and posteriorly on the spiny lobster Jasus edwardsii and the crayfish Paranephrops zealandicus. In our laboratory we have previously used the methods of selective extracellular recording described here to record from the central, sensory and motor systems of the crab Cancer pagurus (Neil et al, 2022) and the Norway lobster Nephrops norvegicus (Albalat et al, 2022).…”

“…On the other hand, Fregin and Bickmeyer (2016) analysed changes in neuronal activity in lobsters in response to mechanical stimulation to different body parts (antenna and eyes, telson, walking legs) following anaesthesia and various stunning methods, but made no simultaneous measures of behavioural indicators of sensibility. Other studies also divide into those that used behavioural indicators alone (Roth and Grimsbø, 2016;Weineck et al, 2018;Astanasoff et al, 2022) and those that used only neurological methods (Albalat et al, 2022;Neil et al, 2022;Kells et al, 2023) (Table 1). Therefore, there is a need for a more comprehensive and integrated approach in which neuronal activity equivalent to the vertebrate EEG, which could include sensory evoked potentials to somatosensory and visual stimuli (Horridge and Sandeman, 1964;Gregory and Wotton, 1987;Hjelmstedt et al, 2022), is correlated with clearly observable body movements and other behavioural measures.…”