Assessment of animal welfare in stunning and slaughtering of farmed fish

These are the main conclusions in an assessment conducted by the Norwegian Scientific Committee for Food and Environment (VKM) for the Norwegian Food Safety Authority.

Background

Millions of farmed fish are slaughtered in Norway each year, and legislation is intended to protect the welfare of fish during the slaughter process. There is a requirement that all farmed individuals must be stunned and rendered and kept unconscious before being killed.

VKM has summarised available knowledge and assessed animal welfare during slaughter, as well as investigated the documentation criteria necessary for different species with the various stunning and slaughter methods.

Conclusions

VKM has assessed electrical and percussive stunning methods. “We found limited documentation for how long fish remain unconscious or what proportion of the fish are not sufficiently stunned at killing”, says Åsa Espmark, Scientific leader of the report. “This should be documented to prevent the fish from experiencing stress and pain during the slaughter process. Moreover, inadequate stunning and unnecessary suffering may occur when fish enter tail-first or too many fish enter the machines simultaneously. How often this occurs is not sufficiently documented.

The report includes fish species farmed in Norway. These are Atlantic salmon, rainbow trout, Arctic char, sea trout, Atlantic halibut, European turbot, Atlantic cod, spotted wolffish, and yellowtail kingfish. Additionally, the report includes fish used to combat salmon lice (lumpfish, ballan wrasse, goldsinny wrasse, corkwing wrasse, and rock cook). Wild fish (saithe, haddock) that might enter the net pens during the production phase are also included. Different fish species have different anatomy, physiology, and behaviour, which affects the effectiveness of stunning and slaughter. Particularly for bottom-dwelling fish (halibut, turbot, spotted wolffish), individual variations in brain location affect the efficiency of slaughter methods. Animal welfare may be reduced when the machines are not properly adjusted to the species and size of fish. VKM found some knowledge about salmon, but it's uncertain if this transferrable to other species.

VKM concludes there is a lack of documentation ensuring that fish remain unconscious until death by exsanguination. The time from severance of blood vessel to brain activity ceases varies between species and is not well documented. “The lack of knowledge can affect the animal welfare”, Espmark says.

There is a lack of data on the relationship between measurement of electrical activity of the brain (EEG) and indicators of behaviour and physiology, both to document that the fish are unconscious after stunning and dead after exsanguination. This documentation is lacking for all the fish species assessed in the report.

VKM provides independent scientific assessments on issues relevant to environmental and food safety. VKM does not offer advice or take a position on how risks should be managed.