Evaluating vitality and predicting mortality in spot prawn, Pandalus platyceros, using reflex behaviors

Evaluating vitality and predicting mortality in commercially exploited crustaceans is increasingly important for reducing discard mortality and for improving handling and shipping for live markets. A suite of 10 reflex actions were identified in spot prawns (Pandalus platyceros) that vary in sensitivity to injury and type of stressor. After establishing a baseline for stereotypic reflexes, prawns were subjected to physiological stress (emersion up to 60 min) and physical trauma (dropping). The prawns were tolerant of air exposure up to 40 min, but susceptible to injuries from dropping and the results within treatments were variable. However, mortality of individuals over a 30-day recovery period was closely related to a simple reflex impairment score calculated as the sum of reflexes lost (range = 0-10) and the effects of different injuries were additive. Logistic regression indicated that reflex impairment was an excellent predictor of delayed mortality (87.5% correct predictions) across prawn size (35-48 mm carapace length) and treatment types. A sigmoid curve describing the relationship between impairment and mortality was termed a Reflex Action Mortality Predictor. This RAMP approach should be a valuable tool in practical experiments related to both discard mortality and handling live crustaceans without the need for tagging or long-term holding.