Do fish feel pain?

Factual Questions
21

Although I’m now at home and can’t ask him for the specific examples he’s cited in the past, I know that my supervisor (the head vet at a large public display Aquarium) has responded in the affirmative on numerous occasions when asked this question. Fish do have nervous systems that, although different from our own, can respond to both positive and negative stimuli. The reason you may not see any obvious signs of discomfort in an injured fish is the same reason you rarely see signs of discomfort in any injured wild animal until the problem is very severe–it’s a survival mechanism. Any animal that appears weakened becomes a prime target for predation or intra-species aggression. Fish (and amphibians, birds, reptiles, and mammals for that matter) are often the target of tank/cage-mate aggression if they are weaker or smaller. The fact that wild animals disguise their symptoms as much as possible is one of the many factors that make being an exotic animal vet so very challenging.

What is fascinating, though, is the resilience some animals show to trauma. I’ve seen pictures of a fish caught out from the Bush River in Edgewood, MD as part of a study that had survived several years and was apparently doing quite well with a large hook in its intestinal tract. The fish had just walled off the hook with immune cells.

*taddycat wrote *

This is scary. There are some fish anesthetics available that any fish vet worth his salt should be aware of (our drug of choice is known as MS-222; clove oil has also been studied). The dosage varies widely from species to species, but most fish can be anesthetized by placing them in an anestheic-containing bath (and it works with fresh or salt water). We also have an anesthetic machine that runs MS-222-containing water over the gills of a fish; very useful for extensive procedures.
Michele

22

It seems to me that the question is less about receiving stimulus from pain receptors, then about the experience we call suffering.
If a sea slug can sense damage in the few nerves that it has, does this mean it is actually experiencing anything remotely like what we experience?
Given the tiny tiny brains on fish, I would suspect they don’t feel much in the way of suffering, although they probably do react to stimulus from nerves meant to sense damage.

23

Some fish are a lot more sensitive than others. Carp have extremely delicate mouths (and that moustache thing). Supposedly, they can detect the protruding tip of a hook embedded in a dough-ball. Also supposedly, they won’t fully take the bait if they detect taught fishing line. A common nickname for them is “trumpetmouth.”

I refuse to fish for these guys because even though they are huge, they can be easily injured. (Well, that and they’re a pain in the ass to fish for. All right, dammit. They’re too smart for me.)

Anyway, while I was reading up on carp mouths, I ran across this site. Here is an interesting quote:

“The carp has an ability to sense touch through its lateral line. The lateral line on a carp which runs from its head to its tail is made up of very fine fluid filled tubes which open to the outside by tiny pores. Similar to hairs they can detect very slight movements in the water which assist them when locating potential good food sources and detecting items to avoid.”

I don’t know if koi are carp, or if they’re just closely related, but I bet they both have that “lateral line.” It doesn’t seem to cover the entire side of the fish, and it doesn’t seem to be precicely like the sense of touch that humans have. Maybe if you avoid the lateral line, the fish can’t detect that it’s being cut. Just a guess.