Animal Health and Welfare
Risk assessment of the use of gas, percussive stunning and electricity in the slaughtering of fish
Report no: 2010: 28
The Norwegian Scientific Committee for Food Safety (VKM) has on request from The Norwegian Food Safety Authority (Mattilsynet) assessed the risk of the fish suffering when it is anesthetized by gas, blows to the head (percussive stunning) or with electricity in connection with slaughtering.
The Ministry of Fisheries and Coastal Affairs (FKD) has prolonged the ban on the use of CO2 to anesthetize fish in connection with slaughtering.
FKD thus asked the Norwegian Food Safety Authority for a new assessment of the various methods of anesthesia and combinations of these.
The Norwegian Food Safety Authority has accordingly requested VKM to conduct a risk assessment of the use of gas, percussive stunning and electricity in the slaughtering of fish.
Electric anaesthesia or blow machine most humane
The VKM Panel on Animal Health and Welfare has been responsible for the assessment. Based on the existing scientific literature, the Panel finds that electric anesthesia or percussive stunning are the most humane methods of anesthesia. However, both methods require frequent surveillance of anesthetized fish, daily control of relevant settings on the equipment and that the equipment is well maintained.
VKM is of the opinion that the use of carbon dioxide (CO2) as anaesthetic is related to great risk of the fish suffering. The fish shows quite extreme flight behaviour before it looses the ability to move, several minutes before it is anesthetized. Thus the fish may be bled or eviscerated when conscious that can imply that the fish experiences pain and discomfort.
It is also a great risk that fish that have been anesthetized with CO2 temporarily regains consciousness before it dies of blood loss.
Nitrogen gas seems unsuitable for stunning of fish before slaughter, since it leads to a high level of stress and extreme flight response. Other inert gases are as far as is known not tested, but in theory gases that only work by displacing oxygen in the water are expected to cause reactions in the fish.
Carbon monoxide (CO) anesthetizes the fish seemingly without the fish noticing the gas, but this is not clearly scientifically documented. Besides, this method is still under development, and it is uncertain whether CO will be used commercially alone or in combination with other methods of anesthesia.
Treatment in VKM
The VKM Scientific Panel on Animal Health and Welfare has been responsible for this risk assessment. Two ad hoc working groups prepared a basis for the risk assessment. Panel member Brit Hjeltnes managed both groups.
The first three questions were examined by Hjeltnes together with Erik Slinde (The Institute of Marine Research), Rolf Erik Olsen and Rune Waagbø (members of the Panel). The fourth question, and an assembly of all the questions, were treated by Brit Hjeltnes together with Ulf Erikson (member of the panel) and Cecilie Mejdell (The National Veterinary Institute).