Assessing Stress and Predicting Mortality in Economically Significant Crustaceans

Reducing animal stress and mortality associated with bycatch and discard in fishing, aquaculture, and live-market trade depends upon improvements in fishing gear and the practices employed in capture, holding, handling, and transport. Several approaches have been used to evaluate the likely mortality of commercially important crustaceans: (1) assess external injuries assuming a direct relationship to mortality, (2) extrapolate from direct observations of mortality under specific environmental conditions and handling practices, (3) evaluate the physiological condition of test animals to predict the associated mortality, and (4) assess behavioral indicators of vitality. Intrinsic variables, such as animal size, gender, and shell condition, and external variables, such as season, fishing and environmental conditions, and type of injury (physiological and mechanical), all have large effects on the complex interactions between stressors and mortality. This review shows that physiological parameters provide insight into the mechanisms of stress and stress responses, but they are often unrelated to mortality outcomes, and the methods are difficult and expensive to carry out in routine field or factory applications. In contrast, behavioral indicators, particularly those utilizing observations on multiple reflex actions, can provide excellent tools where predicting mortality is the primary goal.