Depending on species and geographical location, fish may be killed by a blow to the head, asphyxiation out of water, carbon dioxide exposure, very low temperatures on ice beds or bleeding without stunning. These can take from minutes to hours to induce insensibility and are believed to cause considerable pain and suffering.
With fish welfare and humane slaughter methods drawing increasing attention, in November 2019 the UK Humane Slaughter Association announced its support for a systematic study into the humane capture and slaughter of fish that are caught for food on a commercial scale. Up to £200,000 has been made available for research into the development and use of ways to minimise pain or distress in wild-caught fish.
Percussive and electrical stunning are two methods that offer some potential towards improving humaneness. They’re particularly suitable in commercial fishing, where large numbers of fish need to be killed rapidly.
Blue North Fisheries in Seattle fishes for cod in Alaskan waters. The company has been making innovative strides in how its fish are harvested on board its longliner Blue North. In 2014, Blue North also launched its Humane Harvest Initiative, calling for new practices to allow fish to be harvested more humanely.
‘We were familiar with humane slaughter practices in the livestock industry,’ said Blue North’s founder Michael Burns. ‘When we were designing our boat, we wondered whether we could transfer some of those practices to fish.’
Blue North developed an electrified table that knocks cod unconscious within a second of being removed from the water, with a direct current of around 32 volts. The table is positively and negatively charged, and the fish are dragged across it and stunned. Once their nervous systems have been rendered asleep, hooks are removed and the fish cut. Michael Burns says that when stress is reduced, less adrenaline, noradrenaline and cortisol are released into the flesh, improving meat quality and nutritional value.
‘Studies at Washington State University show that humane harvesting results in better quality meat with a longer shelf life,” he said. “In a fish that’s stressed, adrenaline and cortisol are pumped into its system and that can alter the amino acids and proteins that are nutritious. It’s all about reducing stress before slaughter. We believe that fish do feel and suffer pain, and they certainly undergo stress.’
The stunning table has also benefitted the crew by giving them better control over their catch during slaughtering. Gripping and holding the fish in the right place has become quicker and easier, before the gills are cut to enable bleeding. Blue North is working to encourage other harvesters to reduce any stress, pain and fear in the fish they catch.
Fish handling systems developer Optimar in Norway also focuses on the humane handling of fish. Their electrical stunner is suitable for species including salmon, trout and cod, and is similar to a conveyor belt with electrical fingers hanging from above like a curtain. The fish slide into the conveyor belt and are stunned instantly. Around 300 systems are available for aquaculture and 50 for commercial fisheries.
‘Stunning is humane,’ said Frode Kjølås, EVP Aqua and Concepts at Optimar.
‘A fish with a lower stress level that’s stunned immediately has less blood in its muscles, making it easier to bleed. When you can stun a fish immediately, you can start processing it immediately. This leads to more consistent production which is good for quality and for the operators.’