There is increasing evidence that rendering fish unconscious to minimise struggling before death provides ethical and economic benefits, and Nichimo’s electric stunning devices are expected to shine a light on fish welfare in Japan, and offer fisheries more effective operations.
With a comprehensive line of products and services from fishing nets and gear to fishing electronics and boat building, its latest support for Japan’s fisheries and marine industries is electric stunning devices that are designed to render fish immediately unconscious once they have been removed from the water.
This makes the fish easier to handle and reduces the workload in ikejime – the neutralisation of the fish’s nervous system when it comes out of the water and draining of its blood. Other advantages include increased harvest speed, and better control over the decline in fish quality that can result from incidents such as bruising or internal bleeding.
‘Nichimo produces two types of stunning device,’ said Takahiro Morioka of General Affairs at Nichimo.
‘One is an electrified table that knocks the fish unconscious within a second of being removed from the water via a pump. The table is positively and negatively charged, and the fish are dragged across it and stunned. The other involves stunning a fixed amount of fish by running an electric current through a net that has been used to take fish from the water. Nichimo is the only company in Japan that produces these devices, which are used in aquaculture and fixed set-net fisheries.’
Once the fish have been stunned, gripping and holding them in the right place before ikejime becomes much quicker and easier. Electric stunning also results in a quick depletion of adenosine triphosphate (ATP) in skeletal muscle and a significant reduction in stress levels, which can improve flesh quality and nutritional value. Humane slaughter is achieved if the fish becomes insensible very soon after exposure to an electric field and remains insensible until death.
‘The key to electric stunning is to reduce any stress in the fish before they are slaughtered,’ Takahiro Morioka said.
‘hen fish are stressed, various negative physical changes occur because adrenaline and cortisol are being pumped into their systems. This changes their amino acids and proteins, things that are nutritious for the consumer. To ensure that we prevent this, we conduct regular experiments using electricity by adjusting the strength of electric fields and measuring how long we need to administer them for. Exposure to an electric field that is too weak may result in paralysis rather than insensibility. Meanwhile there is a range of acceptable electric fields which, with a suitable exposure duration, can result in permanent insensibility. We also measure how long it takes from the moment a fish is stunned until it starts swimming again.’
Nichimo’s devices have been tested and used on salmon in Japan, in particular around Ishinomaki in the northeast. Smaller experiments are also being conducted on other species such as Japanese horse mackerel and yellowtail. Salmon has shown the most success so far, says Morioka, mainly because numerical data on electric fields for salmon are clearer than Japanese horse mackerel and yellowtail.
‘With some species it’s always possible that they will die rather than become unconscious,’ Takahiro Morioka said.
‘The size and strength of the fish, as well as the way they swim, are important factors when it comes to electric stunning. Our work so far shows that salmon are the easiest to work with, so our aim now is to keep improving our systems to stun salmon as efficiently and humanely as we can before moving on to other species.’
Hopes are high that fishing operators and fish farms will be keen to adopt Nichimo’s devices in light of an increasing commitment to animal welfare standards in Japan. Although not as advanced in this field as other parts of the world, more companies in Japan appear eager to improve their welfare standards for fish.