Stress induced by hooking, net towing, elevated sea water temperature and air in sablefish: lack of concordance between mortality and physiological measures of stress

In a series of laboratory studies designed to simulate bycatch processes. s ablefish Anoplopoma fimbria were either hooked for up to 24 h or towed in a net for 4 h and then subjected to an abrupt transfer to elevated sea water temperature and air. Mortality did not result from hooking or net towing f ollowed by exposure to air, but increased for both capture methods as fish were exposed to elevated temperatures, reflecting the magnifying effect of elevated temperature on mortality. Hooking and exposure to air resulted in increased plasma cortisol and lactate concentrations, while the combination of hooking and exposure to elevated temperature and air resulted in increa sed lactate and potassium concentrations. In fish that were towed in a net and exposed to air. cortisol, lactate. potassium and sodium concentrations increased. but when subjected to elevated temperature and air, no further i ncreases occurred above the concentrations induced by net towing and air, s uggesting a possible maximum of the physiological stress response. The resu lts suggest that caution should be exercised when using physiological measu res to quantify stress induced by capture and exposure to elevated temperat ure and air. that ultimately result in mortality, since the connections bet ween physiological stress and mortality in bycatch processes remain to be f ully understood.