Welfare science of grading procedures in salmon aquaculture, covering the stress of repeated size-sorting, injury risks, and best practice protocols for minimizing welfare harm during routine management.
Salmon grading is a routine aquaculture management practice whose welfare impacts are often underestimated because each event appears brief and manageable. The cumulative welfare burden across multiple grading events throughout the production cycle is substantial — each event causes acute stress that requires recovery, and the number of events experienced over the farming period means some salmon face many hours of total stress exposure from grading alone. Best practice minimizes the number of grading events to only those operationally necessary, optimizes water quality and temperature during events, minimizes handling duration and mechanical injury, and provides recovery conditions that restore welfare promptly. The welfare science of grading should be integrated into standard operating procedures at all salmon farms.