25/02/2013 13:39 GMT | Updated 27/04/2013 06:12 BST

Should We Care That Fish Might Feel Pain? A Case for the Vegan Option Continued

"Fish do not even suffer when they are hooked and fighting for the lives". So says the Daily Mail reporting on the most recently published research ('Can fish really feel pain?' Rose J D et al) on what fish might feel. This suggests that the responses of fish are basic and instinctive and that they lack any conscious feelings or perception of pain. But other researchers (like Calum Brown et al in a paper titled 'Fish Cognition and Behaviour') are equally sure that fish feel pain in the same way that birds and mammals do. They claim their findings show that fish are intelligent; that they have long-term memories; can recognize individual shoal mates; and have the ability to feel pain and stress.

When it comes to judging whether fish - and all the other aquatic animals we use for food - are sentient beings there seem to be several reasons why the research findings are so confusing.

The unlikeness between animals that live in water and the land animals we are so familiar with is not just physical. The way aquatic animals interact with each other is utterly alien and so is the environment they live in. For instance fish communicate with chemicals and by making sounds with their swim bladders. Lobsters smell with their antennae and taste with the hairs on their legs; but like land animals they also form hierarchies and remember those they have fought in the past. Squid, of all invertebrates, have the largest brains and their senses are the most highly developed: they communicate by changing colour and in a fraction of a second can alter the colour and pattern of their skins.

Perhaps we might never know whether - or to what extent - they suffer. Since the capacity to learn and to feel pain and fear are necessary survival mechanisms, does not common sense tells us that it is likely that fish, crustaceans and also molluscs like squid and octopus must have these senses too?

In trawling nets, fish are trapped with rocks, debris and other sea life and dragged along the bottom of the sea for hours. Surely, in these circumstances, they must suffer fear, pain and stress? And what might they feel when they are caught in huge nets and the pressure from the weight of the catch ruptures swim bladders, pops out eyes and pushes stomachs out through mouths? Do fish feel pain when they are gutted alive? Do line-caught fish feel pain when they are impaled on hooks and those hooks ripped from their mouths? When they are left to suffocate in air do they feel the way land animals do when they are drowning? Are tuna in a state of panic when they are caught in net cages and towed slowly to feedlots for fattening and slaughter? When farmed salmon skitter on their tails in short bursts across the surface of their pens is this an indication of stress and suffering? Do farmed sea bass and halibut feel distressed when they develop severe cataracts and bleeding corneas? Do female tiger prawns feel pain when their eyes are ripped out to encourage them to spawn? When lobsters writhe in boiling water are they experiencing agonising death throes? Might octopuses feel pain when they are snagged on jigging lines set with barbed hooks?

To those who are so sure that these animals do not suffer here is the question. What is it that makes you so certain?