reds,
I'm pretty confident that fish can feel pain. They certainly react similarly to other animals when they encounter stimuli that would cause pain in other animals. And medically, fish have a very advanced nervous system and they have nerves similar to ours. Now, where they feel pain is questionable and probably varies by species. On some fish the lip is kind of like extended fingernails on people, no nerves or blood, etc. On others, there are nerves and blood in the lips.
I'm also pretty sure fish, as well as other animals, are smarter than we give them credit for, at least in some things. Animals are only intelligent in ways that help them survive or breed. Fish have pretty good memories, they'll recognize a green drake weeks after they've seen the last one, and a fish will move into "its" individual feeding lie in anticipation BEFORE a hatch begins. And we all know in places with high fishing pressure, the fish are more difficult to catch because they inspect their prey a little better. Call it fear, skittishness, or whatever, it does absolutely indicate some sort of memory of a bad experience.
So memory and responding to stimuli, yes. Learning, yes, but its probably just experience based. Actual reasoning is doubtful, but I wouldn't absolutely say its impossible on a limited scale.
I believe all of this to be true. However, I also agree mostly with FarmerDave regarding animal rights. Animals don't have rights, but humans have societal responsibilities. If you choose to own a dog, you do so for your or your family's enjoyment, and it is your responsibility to keep the dog happy enough so that it isn't a danger to other people, not abandon it as to create a feral animal, and not put the burden of it onto others (like taking it to a shelter when you no longer want it). Anything beyond that is not a responsibility but can be worthwhile, a healthy and friendly animal is more enjoyable, and we take them to vets and such for that reason. For livestock, an animal is an investment, and taking care of the animal helps you get the maximum out of your investment, its part of making a living.
IMO, there was nothing morally wrong with Mike Vick fighting dogs. He was, however, rearing and keeping animals that were dangerous to other PEOPLE, and creating offspring which were bred to be mean, some of which will enter the pet trade, which makes more dogs dangerous to other people. Thats why the laws against dogfighting exist.
Humans are animals, and the ONLY reason even we have rights, is that our society has correctly decided that more of us will live happy lives if we all abide by these rules. Wildlife management, like the fisheries people PETA is lobbying with this campaign, are not governed by what's best for the animals, they're governed by whats best for people in the long run. It's nature, and we're ensuring our survival, the same as the bear eating the salmon. Fishing, hunting, etc. are necessary for our survival, or at the very least not harmful. Overfishing and overhunting, however, endanger our long term survival.