Live Chilling and Carbon Dioxide Sedation at Slaughter of Farmed Atlantic Salmon: A Description of a Number of Commercial Case Studies

ABSTRACT

Eleven commercial processing lines for the slaughter of Atlantic salmon were evaluated to investigate the efficiency of the refrigerated seawater live chilling method with respect to stunning fish and reducing body temperature. The method is commonly used in the Norwegian salmon industry to both stun and chill fish before killing. Carbon dioxide gas was added to the live chilling tanks, or in some cases, to a subsequent carbon dioxide stunning tank. Criteria used for evaluation were water quality parameters (dissolved oxygen, carbon dioxide, pH, temperature, total ammonium, ammonia, alkalinity, color, total organic carbon, and ferric ion), fish behavior, white muscle pH, and body and core temperatures. At two processing plants, fillet quality (Roche color, texture, ultimate pH, and water content) was also determined. The results are discussed in terms of fish acclimation temperatures, water quality, welfare, handling stress, chilling efficiency, pre-live chilling factors, refrigerated seawater live chilling process parameters, and fillet quality. Even though the live chilling method can be used to minimize fish handling stress during slaughter and may serve as an efficient chilling method, it was found in most cases that under commercial conditions when large biomasses were slaughtered, both handling stress and chilling efficiency were less than optimal. However, no adverse effects on the fillet texture and color were observed as a result of fish processing.

KEYWORDS:

• Fish processing
• live chilling
• carbon dioxide anesthesia
• water quality
• handling stress
• fish welfare
• Atlantic salmon

ACKNOWLEDGMENTS

The author would like to thank all involved personnel at the processing plants and at SINTEF Fisheries and Aquaculture, as well as Jan Erik Steen (Octopus Marine Consultancy) for their kind co-operation and technical assistance in carrying out the various projects. Thanks also to The Research Council of Norway for financial support for the preparation of the manuscript (NFR project No. I45634/140 –‘Efficient and economic sustainable fish processing industry’).