Stunning and bleeding of cod onboard fishing vessel – Final report

Summary

In study 1, we were to see whether we could slaughter the cod directly after landing with the help of either electrical or mechanical percussive stunning followed by temporary storage under chilled water or air before bleeding. This is to hinder that the fish pumps blood out into the muscle, which becomes red. Fish that received mechanical percussive stunning, that were kept in water, had a relatively even spread of remaining blood. The groups treated with electricity had an increased amount of remaining blood in the muscle, especially the group store in air. This can be due to individual fish that woke up during the study. The control group had a clear increase in residual blood with increased storage time in air. In study 2 the results showed that, the temperature of water used for bleeds appears to have little influence on the residual blood in the fish. In study 3, it was investigated if the bleeding was influence by difference blood draining methods where the cod were either hanging in air or laying in water. The results showed that the method of blood draining (in air or water) was not decisive for how much blood was lost by the fish or the residual blood level when the bleeding was done shortly after stunning. However, there was a tendency for the groups that were bled out in water to have a higher blood loss in percent. In study 4, the results show that the majority of the blood is lost during the first three minutes of bleeding and contains nearly the same level of residual blood as those fish bled for 30 minutes. It must be pointed out that this was just an initial test with 10 fish per group. There clearly must be additional follow-up studies to verify this data. If the bleeding time is short with regard to blood removal, it may be important for the processing plant organization on board vessels and the slaughter process of fish.