Bulk oxygen uptake measured with over 60,000 kg of adult salmon during live-haul transportation at sea

We are unaware of any assessments of fish welfare during live-hauling of adult salmon in very high numbers (> 10,000 fish) and at high density (∼100 kg/m3) and yet live transport of adult salmon from sea cages to processing plants is now a common practice. Here we report on the bulk metabolic rate of adult Atlantic salmon (Salmo salar L.) during transport from a sea farm off the west coast of Vancouver Island, BC, Canada, on board a state-of-the-art live-haul vessel, the Sterling Carrier. Monitoring the oxygen concentrations of the water entering and leaving the flooded holds revealed that oxygen uptake decreased from > 8 mg O2/min/kg to an average < 4 mg O2/min/kg within the first 20 min of the vessel being underway. During the fourth hour of transport, oxygen uptake averaged 3.1 mg O2/min/kg, a value comparable with routine oxygen uptake values measured under laboratory and field conditions for single adult salmon in a swim respirometer. This finding suggests that adult Atlantic salmon quickly recovered from the stress of loading on to the Sterling Carrier. This conclusion was corroborated by visual observations of the fish in the live holds, which revealed that fish faced the water flow and ventilated lightly while slowly cycling their position in a schooling behavior during the 11-h journey. Thus, the live transport conditions on board the Sterling Carrier appeared to promote good welfare of adult Atlantic salmon during the 11-h journey from a sea farm to a processing plant.