A new review carried out at Liverpool University shows there is very little doubt that fish do experience pain – although whether they experience it in the same way as mammals is less clear.
The review was led by Dr Lynne Sneddon, the university’s Director of Bioveterinary Science, who is one of the world’s leading authorities on the subject. In 2002, Sneddon was the first scientist to prove that fish do have ‘nociceptors’ (cells that detect pain) in their mouths.
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Now, after examining the evidence from dozens of studies carried out worldwide, she is more convinced than ever of the need for greater care be taken in our interactions with fish species.
“Be it recreational angling, large-scale fisheries, ornamental fish – any way that we use fish, we need to consider treating them better, as if they experience pain,” she says. “We should treat them with the same consideration we afford to mammals and birds.”
While the research shows that fish do feel pain and adapt their behaviour accordingly, the circumstances in which they do so can differ from humans. Fish are far less sensitive to cold, for instance, but much more sensitive to pressure.
“Their mechanical thresholds – the amount of pressure you have to apply to stimulate the nociceptors – are much lower than in mammals,” says Dr Sneddon. “It’s actually quite similar to the human cornea, so handling them is likely to cause pain.”
It’s therefore hoped that, as well as the obvious implications for animal husbandry and welfare, the research will shed new light on how the evolution of pain detection mechanisms in animals is affected by their environment. The next step for Dr Sneddon, meanwhile, is to look at how pain signals are processed by fish’s brains.
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