Adapting Aquaculture Technology for Fish Vessels to Improve Fillet Quality

In this issue of JAFPT, we have a paper looking at the potential of using electrical immobilization technology for quality improvement of cod, saithe, and haddock harvested by fishing vessels. All of these fish are bled after capture on board fishing vessels. However, as the authors point out, bleeding does not always occur when fish are still alive or in the time period needed (30 min to 1 h) to maximize removal of blood. The resultant fillets can be downgraded due to discoloration. Electrical immobilization is being proposed as a means to not only humanely slaughter fish brought on vessels alive but to also facilitate their post-harvest handling and bleeding. Electrical immobilization is most commonly used in land-based animal production systems for humane slaughter. It has been adapted for aquaculture to make it easier to handle fish, improve bleeding, and to prevent fillet discoloration. There are known benefits to ultimate meat quality when you reduce the effects of animal struggle prior to harvest. Aside from the obvious damage (bruising) that can occur if fish are struggling when being handled, meat functional quality is also impacted by acidification rate. During struggle, oxygen is quickly utilized and anaerobic glycogen reduction occurs, resulting in the production of lactic acid in the muscle. Rapid acidification, due to struggle while meat is warm (not bled out yet), can cause myosin denaturation and reduce its ability to hold water. We see the results of this effect in an increased rate in driploss. Although this paper is focused on determining minimum voltages necessary for proper stunning, the authors do report a significant difference in initial muscle pH as a result of treatments. It would be interesting to investigate how those initial differences impacted myosin water holding ability, fish meat driploss, and ultimately shelf-life. This area is relatively new for fish harvesting on vessels, and I am excited to see scientists for aquatic systems working to push the boundaries of technology to improve harvest and handling on our fishing vessels.

We hope you enjoy reading this edition of JAFPT.