Physiological Changes as a Measure of Crustacean Welfare under Different Standardized Stunning Techniques: Cooling and Electroshock

Abstract

Simple SummaryPhysiological measures were examined during stunning of three commercially important crustacean species: crab, crayfish, and shrimp in an ice slurry or with electroshock. Neural circuits for sensory-central nervous system (CNS)-cardiac response and sensory-CNS-skeletal muscle were examined. Heart rate of shrimp was the most affected by both stunning methods, followed by crayfish, then crabs. Ice slurry and electroshocking may paralyze crabs, but neural circuits are still functional; however, in shrimp and crayfish the neural responses are absent utilizing the same protocols. The use of stunning methods should vary depending on species and slaughter method. Interpretation of behavioral signs should be supported by further research into related physiological processes to objectively validate its meaning.AbstractStunning of edible crustaceans to reduce sensory perception prior and during slaughter is an important topic in animal welfare. The purpose of this project was to determine how neural circuits were affected during stunning by examining the physiological function of neural circuits. The central nervous system circuit to a cardiac or skeletal muscle response was examined. Three commercially important crustacean species were utilized for stunning by immersion in an ice slurry below 4 °C and by electrocution; both practices are used in the seafood industry. The blue crab (Callinectes sapidus), the red swamp crayfish (Procambarus clarkii), and the whiteleg shrimp (Litopenaeus vannamei) responded differently to stunning by cold and electric shock. Immersion in ice slurry induced sedation within seconds in crayfish and shrimp but not crabs and cardiac function was reduced fastest in shrimp. However, crabs could retain a functional neural circuit over the same time when shrimp and crayfish were nonresponsive. An electroshock of 10 s paralyzed all three species and subsequently decreased heart rate within 1 min and then heart rate increased but resulted in irregularity over time. Further research is needed to study a state of responsiveness by these methods.

Physiological and Behavioral Indicators to Measure Crustacean Welfare

“…General care of animals prior to slaughter and techniques to ensure efficient stunning are continually being investigated to make the process of slaughter for human consumption more humane [1,2,3]. Crustaceans are a substantial source of animal protein for human consumption and crayfish alone represent 12% of all farmed Crustacea, second only to shrimp [4].…”

“…The argument against the conclusion that crustaceans ‘feel’ pain is rooted in the fact that behavior as a measure for pain perception is not entirely reliable and reproducible [2]. It is only recently that physiological measures in crustaceans have been used alongside behavioral indicators to help draw conclusions on their sensory perception and thus welfare [3,10,11]. The approaches to stun crustaceans with the quickest and the least stressful methods have been examined since the 1950s [12].…”

“…The approaches to stun crustaceans with the quickest and the least stressful methods have been examined since the 1950s [12]. Approaches include rapid cooling, rapid and slow warming, exposure to CO 2 , and electrical stunning [2,3,10,13,14]. However, the variety of crustacean species and their adaptation to different environments, as well as their various sizes and shapes, results in a wide array of physiological responses to the stunning methods available, making it difficult to adopt a universal method.…”

“…However, the variety of crustacean species and their adaptation to different environments, as well as their various sizes and shapes, results in a wide array of physiological responses to the stunning methods available, making it difficult to adopt a universal method. A marine shrimp adapted to warm environments (27–28 °C) responds differently than a lobster ( Homarus americanus ) or a blue crab ( Callinectes sapidus ) conditioned to cold (10 °C) when stunned by cold-shock (~4 °C) [3]. The electrical stunning technique requires consideration of varying current strengths for fresh and sea water crustaceans as well as size differences and types of crustaceans [3,13,14].…”

“…A marine shrimp adapted to warm environments (27–28 °C) responds differently than a lobster ( Homarus americanus ) or a blue crab ( Callinectes sapidus ) conditioned to cold (10 °C) when stunned by cold-shock (~4 °C) [3]. The electrical stunning technique requires consideration of varying current strengths for fresh and sea water crustaceans as well as size differences and types of crustaceans [3,13,14].…”