Using bulk oxygen uptake to assess the welfare of adult Atlantic salmon, Salmo salar, during commercial live-haul transport

Adult Atlantic salmon are routinely live-haul transported at high densities for long periods of time as one of the last intensive processes in a commercial aquaculture operation before fish processing. Therefore, ensuring the welfare of these fish during transport is critical to product quality. As an indirect assessment of fish welfare during transport, flow-through respirometry was used on board a commercial live-haul vessel to measure bulk oxygen uptake rate ((M) over dotO(2)) for large masses of salmon being transported for over 10 h. Bulk (M) over dotO(2) was 2.98 +/- 0.13 mg O-2 min(-1) kg(-1) after 1 h of transport and decreased to 2.03 +/- 0.14 mg O-2 min(-1) kg(-1) after 10 h of transport. These rates of oxygen uptake were comparable to the routine oxygen uptake rates previously measured in tank-raised adult Atlantic salmon and in individual wild Pacific salmonids using swim-respirometers. Therefore, the values for bulk (M) over dotO(2) suggest that salmon recovered quickly from any stress of loading and stress was low throughout the 10 h of live-haul, perhaps indicating that salmon welfare was acceptable during the live-haul transport procedures that we followed. Using a mixed effects regression model, we found that bulk (M) over dotO(2) was positively affected by water temperature, and calculated the temperature coefficient (Q(10)) to be 1.9-2.0 between 7.8 and 15.0 degrees C. The model also showed that loading densities between 62 and 150 kg m(-3) did not significantly affect bulk (M) over dotO(2). (C) 2008 Elsevier B.V. All rights reserved.