Continuous physiological welfare evaluation of European whitefish (Coregonus lavaretus) during common aquaculture practices leading up to slaughter

European whitefish (Coregonus lavaretus) is an aquaculture species with the potential for expanded cultivation in fresh and brackish waters of Northern Europe. Yet, relatively little species-specific information available regarding stress responses associated welfare implications this captivity. We addressed knowledge gap by using a combination implantable heart rate bio-loggers range traditional indicators (e.g. haematological parameters plasma concentrations cortisol, glucose ions) to comprehensively evaluate physiological freely swimming captivity, as well when subjected practices stressors that commonly occur prior during slaughter. Whitefish appeared recover rapidly from surgery, resting decreased within 36 h stabilize at ~25 beats min?1 next 18 days fish were left undisturbed (i.e. personnel only present feeding fish). In contrast previous studies on farmed rainbow trout Atlantic salmon, did not exhibit clear circadian rhythm, which may be related differences diurnal locomotor activity. also appear have well-developed capacity thermal acclimation rate, daily change period despite increase body temperature ~6.8 11.2 °C. Following acute such crowding transportation, response typically involved transient elevations cortisol glucose, red blood cell swelling, while [K+] decreased. contrast, plummeted following brailing haul brail/net) CO2 exposure slaughter, [Ca2+] significantly increased. An unforeseen finding concerns substantial long-lasting observed held close proximity ~10 m) net pen, mean increased ~32 43 ~34%). This represent innate threat predation, consequently increases allostatic load energetic expenditure alongside salmonids. To conclude, study highlights importance performing long-term, evaluations real settings, provides platform further research aiming determine simultaneously farming predatory prey proximity.