I have been studying, diving with, keeping, selling and eating lobsters for almost 50 years. My family was in the sea food business. They do not feel pain. They feel something I am sure but any animal that can tear off their own claw or leg and eat it does not feel pain. I am certain fish do not feel pain. I have seen many fish with large chunks torn out of them turn around to eat their own intestines. I once had a hippo tang and a triggerfish tore off it's mouth. The hippo just calmly swam around trying to eat even though he had no jaw. I also have caught many fish, particularilly flounder which almost always swallow the hook. Many times after I throw these fish back because they were too small, I caught them again a few minutes later.
I have been studying fish and crustaceans longer than most researchers and they do not feel pain.
Now cows feel pain but most people have leather jackets.
Paul