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Away with CO2
"The salmon actually tries to jump out of the tank that has been added CO2", says Senior Scientist Kjell Midling at Fiskeriforskning.
The authorities are concerned about the welfare of the fish both while it is at the fish farm and when it is going to be slaughtered and sent out in the market. Good fish welfare also results in better quality of the finished product.
The authorities are issuing a new slaughterhouse regulation, and it will soon be illegal to use CO2 as an anaesthetic. This means that most of the approved salmon slaughterhouses in Norway, which together slaughter around 600 million kilos of salmon annually, are facing extensive changes in production.
"The transition from CO2 anaesthesia will perhaps become the greatest challenge for the Norwegian aquaculture industry in 2007", says Midling.
Electrical anaesthesia can cause stress or injuries
 After anaesthetising and killing, the scientists measure, amongst other things, the firmness, temperature and acidity to study the quality of the fish. Photo: Fiskeriforskning. |
Scientists at Fiskeriforskning are well underway with a project to evaluate three Norwegian methods that use electricity instead of CO2 to anaesthetise the salmon before slaughter.
The results show that there is still a way to go before electrical anaesthesia satisfies the requirements for instantaneous anaesthetisation while simultaneously resulting in a salmon with the best possible quality.
"The evaluations at the slaughterhouses showed that fish that were killed using high voltage had severe muscle contractions, many had their spines broken, and there was blood in the fillets."
At too low voltage, the salmon was not anaesthetised but, rather, very stressed and exhausted. This goes against the requirements for instantaneous anaesthetisation and merciful killing, in addition to resulting in a poorer quality fish.
Faster anaesthesia by a hard blow to the head?
The scientists are now testing equipment that anaesthetises the fish by a hard blow to its head. At the Troms Aquaculture Research Station in Skulgambukt outside Troms, an Australian system will also be tested.
"The principle behind the new system is that the fish swims into a canal where it is rendered unconscious by a machine that gives it a quick blow to the head", says Midling in closing.
Previous studies show that after using CO2 on the fish, it only takes about two hours from the time of killing until rigor mortis sets in. When the fish is stunned by a blow to the head, it can take considerably longer before this happens, and this gives the fillet manufacturers more time to process the raw materials.
The studies will be completed during the autumn. They are financed by the Fishery and Aquaculture Industry Research Fund as a part of the programme "Action Plan Salmon". The research is a collaboration between Fiskeriforskning and the National Veterinary Institute.
Would you like further information about this project?
Please contact Senior Scientist Kjell Midling, dir. tel. (+47) 77 62 90 13
TheFishSite News Desk