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The stress of moving out : physiological and behavioural effects of commercial transport on Atlantic salmon (Salmo salar) smolts Nomura, Miki

Abstract

Despite the controversy over environmental sustainability, salmon aquaculture in British Columbia is economically important for many coastal communities and is reported as being the largest agricultural export product for the province. This thesis examined the welfare status of commercially produced Atlantic salmon smolts during transport from freshwater farms to the saltwater net pens using physiology and behaviour to assess transport stress. Smolts were transported first by truck from the freshwater farm to the dock, and then in the flow-through cargo holds of a live-haul vessel to the saltwater net pens. Fish and water were sampled before and after truck transport, and several times aboard the vessel. Assessment of stress was based on measurement of plasma cortisol, glucose, lactate, potassium, sodium and chloride concentrations, as well as behavioural observations made on underwater video footage. Seven transports of fish originating from two different hatcheries were sampled; one was a land-based tank hatchery that required a 30-min drive to the dock, and the other a lake net pen facility that was 90 min to the dock. Analysis of plasma constituents supported previous studies that recovery from the stress accumulated during loading and truck transport can be quite rapid in a live-haul vessel. Underwater video footage, recorded at the freshwater farms and in the cargo holds of the Sterling Carrier, also suggested recovery onboard in that for the most part, behaviour onboard was similar to behaviour at the freshwater farms. There were some significant differences between fish from the two types of hatcheries, particularly in the original hatchery conditions and in their behavioural responses to transport conditions; however, post-transport growth and mortality rates reported by the saltwater farms showed no significant difference. Although fish were subjected to moderately stressful conditions during part of the process, smolt transport as currently carried out by our industry partners reflects good husbandry practices and fish welfare.

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Attribution-NonCommercial-NoDerivatives 4.0 International

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