The world's foremost expert on the subject is Dr. James D. Rose of the University of Wyoming. He's spent 30 years working on questions of neurology, examining data on the responses of animals to painful stimuli. In 2003 Rose published a landmark study in the journal Reviews of Fisheries Science, concluding that animals need specific regions of the cerebral cortex in order to feel pain. And fish do not have them.
But doesn't it hurt to have a hook in your mouth?
There's a big difference between pain and the perception of pain (which scientists call "nociception"). Dr. Rose explained to London's Telegraph newspaper:
"Pain is predicated on awareness … A person who is anaesthetized in an operating theatre will still respond physically to an external stimulus, but he or she will not feel pain. Anyone who has seen a chicken with its head cut off will know that, while its body can respond to stimuli, it cannot be feeling pain."I don't imagine animal-rights activists are very fond of Dr. Rose.
Right you are. People for the Ethical Treatment of Animals (PETA), for instance, operates a misleading "Fishing Hurts" propaganda campaign based on the work of a few "neutral" experts. (PETA says Dr. Rose isn't neutral because he enjoys fishing.) One of PETA's experts is a "Professor of Animal Welfare" who also believes it's cruel to raise faster-growing cows and turkeys. Another is a microbiologist who claims it's "unthinkable that fish do not have pain receptors" -- despite having done no scientific work with fish -- and equates our "lack of justice and compassion to other animals" with human slavery.
It's worth noting that PETA has sought fishing bans in state parks and called for a Constitutional amendment protecting fish. In 2005 when PETA tried to scare fishermen away from their sport by claiming fish contain "poison," campaign director Bruce Friedrich admitted his strategy on an animal-rights mailing list: "For people who don't care about the suffering of fish, I suspect this will terrify them into not eating them."
What about lobsters and crabs? Do they feel pain when they're boiled or steamed?
A 2005 Norwegian study reported that lobsters and crabs don't have the capacity to feel pain either. The British Guardian newspaper detailed the study's findings, explaining that lobsters and crabs have only about 100 thousand neurons. Many vertebrates have upwards of 100 billion.