Do fish feel pain? Unequivocally yes, according to Victoria Braithwaite, a fish biologist here at Penn State. She described how she knows this on The Forum, a radio program on the BBC World Service on 12/18. It's very odd that this wasn't understood until her work -- a paper that garnered much attention by Braithwaite and co-authors was published in 2003 (but has been selectively forgotten or ignored by many) -- but very nice that she's cleared that up. Amazingly, people have long labored under the belief that fish are insensate creatures.
The reasoning behind such views is difficult to understand. Fish certainly avoid danger, but they don't have facial expressions we can read, and they are cold, slimy, primitive creatures (well, relative to us humans, we like to think!). They reproduce like, well, like fish so with such numbers what's the advantage of pain receptions? They have primitive brains (relative to ours).
Or is it more than just the arrogance that goes with the angler's realization that we're in charge? Not so long ago, lobbying was done among life scientists to write to Congress to oppose legislation that might regulate the kinds of experiments that could be done on fish. Our noble peers in biology wanted to be left alone, not constrained, after all! It was even said that pain in lab animals was good for them--yes, it was said!--because it made them resilient to the conditions under which they lived. We're not enamored of bureaucrats who feel they can meddle in our daily research life, but this wholly self-interested campaign-of-convenience by scientists was gross.
Anyway, the idea of piscal pain experience would be more convincing if they had what we would at least recognize as neural pain receptors. In fact, pain wiring was long ago worked out in birds and mammals, perhaps, according to Briathwaite, because it's easier to feel empathy with these creatures. But, even the question of whether fish have the neural wiring that transmits the stimulus to the brain wasn't known until Briathwaite et al.'s work.
And yes, fish do have them! (Sorry, anglers and zebrafish torturers!). Transmitting pain information is done in two stages, by two different types of nerve fibers, the A-delta and C fibers. A-delta fibers transmit information about damaging or noxious stimuli instantaneously and the second transmits it more slowly. Fish have both of these nerve types, though in a different ratio from birds and mammals (fish have more of the C type, relative to other vertebrates).
But, says Braithwaite, "finding the fibers themselves doesn't necessarily tell us that the second stage of pain is going on", that when the signal passes up the spinal cord to the brain, the fish becomes aware that it has been damaged. To test this, Braithwaite et al. provided fish with a painful stimulus, either vinegar or bee venom, injecting small amounts into the snout of rainbow trout. They injected saline solution into the snouts of a control group of fish, and found the two groups had very different responses. The respiration rate of those injected with the pain stimulus quickly accelerated and stayed high, and these fish went off their feed, while the control group responded to being handled and injected with increased respiratory rate and not eating, but their respiration quickly went back down and their feeding behavior returned to normal. Which Braithwaite et al. interpreted as clear evidence that they feel pain.
But does it matter? Is it enough to modify their behavior? That is, do the fish respond to pain? Fish have a low tolerance for novelty, so the researchers put Lego objects into the tanks, treated them with pain injections, and observed their behavior. Would they avoid the Legos, as normal? In fact, when treated with pain stimulus, they did approach the novel object, which the researchers interpreted as showing that the fish were distracted from their normal behavior by pain. But, they were able to reverse this with pain relief. They gave the fish some morphine and observed that they again avoided the Legos, as normal. (Are you nauseous yet, given that they knew by now that fish feel pain?)
Braithwaite says that responding to something that is damaging is important evolutionarily, and only vertebrates can have the experience of learning from pain, and learning to avoid it. But, do fish suffer when they feel pain? Is that an odd question? Isn't perceiving pain by definition suffering? Is it more than self-centered for us to couch this in terms that relate to our, human, kind of experience? Braithwaite explained that they've found an area in the fish brain that's devoted to processing emotional information, as in other vertebrate brains. It's more rudimentary in fish, but if it's damaged or lesioned, the fish's ability to respond to emotional information is impaired, she said.
And further, do fish have consciousness? Ascribing consciousness to a non-human animal is a tricky area, Braithwaite said. She takes her model of consciousness from Gerald Edelmann, who says that consciousness is modular. She didn't expect to find all the modules we have in fish, but says there is evidence for two of them; 'primary consciousness' and 'phenomenal consciousness'.
Primary consciousness is the ability to create a mental representation of something, and Braithwaite says that fish can do that. That is, they can do spatial mapping. Phenomenal consciousness is how we experience and understand the world. Braithwaite's view is that the fact that fish can learn from experience is evidence that they have phenomenal consciousness, too. And, the evidence of fish consciousness is, to Braithwaite, both evidence that fish can suffer, and that they are deserving of welfare rights, as are birds and mammals -- equivalent to humans. Sport fishermen, especially those who enjoy catch and release fishing, need to consider that fish feel pain, as do fish farmers.
This is all well and good, and it's good to see the old conceit that fish don't feel pain put to rest, but we think there are also lessons here about academic hubris that should, but probably won't be learned. The anthropocentric conceit isn't new, but we're supposed to be scientists, to deal with the real world, not the one we wish were out there! We have bestialized the world except for ourselves. In the west, at least, this might be a consequence of long-standing (convenient) biblical views that God, in His wisdom and compassion, gave us dominion over the fish of the sea, and over the fowl of the air, and over every living thing that moveth upon the earth (does that include bacteria and hookworms?).
Whatever the source, we want to be able to have our will with these beasts and will not welcome the latest piscine bulletin. It's bad enough that after having our experimental will with chimps we have to let them live out their natural life (but not monkeys), and we are not supposed to subject lab mice to torture (as we and our IRBs define it, which turns out to be pretty lenient). But fish?!