Dolphins are notorious for going nuts when hitting a net. Some species will struggle so hard, they break the back of their skull with their neck bones. Actually force the wings (transverse processes) of their cervical vertebrae into the back of their skull. Not convinced it's so much pain, as it is the stress of restraint in that case. There is a whole science for livestock transport that studies the effects of restraint and methods for avoiding deleterious side effects of the stress of transport and restraint. With respect to a fish being penetrated by a spear, I presume it's a combination of pain and restraint stress. The initial "crazy" reaction is likely pain induced, and then once the endorphins/opioids kick in, likely a restraint response. We could really use an anesthesiologist right about now...this is NOT my area of expertise. Guess that means I should shut my pie hole...:fridaySorry, got a few in me and starting to ramble...