Pain is not a respecter of intelligence. We tend to assume that the stupidest individual we know is capable of feeling as much pain as we do. We don't tend to say:
"Well, Agnes is pretty dumb you know. Are we really sure that she felt pain when that truck hit her? Okay. I know she flew 25 feet in the air, let out a blood curdling scream and then thrashed about for ten minutes. But was that just a motor response? Was she really feeling it?"
We just don't. Agnes may be dumb, but pain she most certainly did feel. And yet change it around to say:
Well fish are sometimes pretty dumb you know. Are we really sure that fish felt pain when we hauled it 25 feet in the air with a metal hook in its mouth, juggled it, patted ourselves on the back for a bit, took a picture, then weighed it while all the while it is gasping for air (I did throw it back after all!)" And we aren't so sure.
Fish aren't cuddly. They don't wag their fins at you when you enter the room. They seem distant, aloof, independent, rather like cats really, only without the mitigating fur that is amusing to stroke. Tell me, if you stuck a hook through your cats mouth, dunked him in water and stood and watched while he floundered desperately for air. Would you suspect that might be a painful experience?
Is that same experience painful for a fish though? That is the first question. There is actually rather a lot of science to back up the fact that fish do feel pain.
A group of scientist investigated the sensory system of trout through their responses to injections of bee venom and acetic acid around their mouths. In effect the research was trying to find out whether fish possessed the same kind of pain receptors that have already been identified in amphibians, birds and mammals including humans. And secondly, whether the response to the pain producer (i.e. the bee sting etc) was not just a reflex response which might be akin for example to pressing the belly of a talking barbie doll; but rather an actual adverse reaction to the pain stimulus. Glad to see there are humans who really do care about the harm and suffering to all living creatures great and small ! Basically to anything that can "perceive pain".
What they found was that the fish had 58 such receptors around the mouth and actually reacted at lower levels of pain stimulation than humans, perhaps because their skin is more easily damaged. After the fish were injected with the venom they were observed to show a rocking motion akin to that displayed by other mammals when experiencing stress; they also rubbed their lips on the bottom of the tank and against the walls, and took over twice as long to resume feeding than a control group. In short, they felt pain and reacted to it.
One of the most interesting results of the study is the increase in the length of time it takes for the fish to resume feeding after experiencing pain. This is akin to you falling off your bike as a child and being somewhat reluctant to get back on. Literally the pain is not then just a physical sensation it is psychological. Our poor trout were stressed out. And whilst they are unlikely to win any 'Brain of the Month' awards, it seems churlish to dismiss the feelings they are experiencing as irrelevant simply because they are not making all the mental distinctions we might. Pain is pain when you are the one experiencing it.
And it's not just trout. Another study in the late 80's investigated the reaction of carp to being caught with a hook and then released. They found that carp that had been caught and then released abstained from feeding for a considerably longer period of time, and showed stress type behavior like making rapid darting movements, spitting, diving and shaking their heads. The study concluded that the fish felt pain from being hooked, but that their behavior was mostly a fear response to possibly being caught again. In effect then, in a similar way that a victim of violent crime may get over the physical injuries quite quickly, but be traumatized for far longer, the fish showed a similar trauma response to being caught.
Sense a pattern emerging here? So, let's go with our common sense here. The world's leading animal charity reckons that even handling your pet fish in a rough way causes them distress. What do you suppose shoving a hook through their mouth, juggling them in the air while you get them on a set of scales and watching them gasp for air might do for their state of mind? Probably not very calming for them I suspect.
But what next? Worms? Wasps? Plants? Should I stop eating asparagus now because it might be having a bad day. If my tomatoes scream out in pain where is there to go? I GOTTA EAT SOMETHING!!!
Calm down. I feel your pain! Just use your head and try to limit it to inflicting it on yourself and the people around you, and not the rest of the planet! Personally I have a simple philosophy when it comes to food and life in general. If it once breathed I don't eat it, and I try not to harm it. Have I ever squashed a worm or splatted a wasp? Absolutely. I try not to make a habit of it, and if I do it is generally an accident. I don't much like wasps and frankly I am not going to start up a 'Wasp Protection League' anytime soon. The less of them in my house the better. But unless they are attacking you or you are allergic to them (in which case splat away - self preservation baby!) then what's the harm in putting a glass around them and letting them fly away into the garden? Who knows, they might even do you a favor and sting that stupid neighbor you don't like!