Sockeye salmon are blue tinged with silver in color while living in the ocean. When they return to spawning grounds, their bodies become red and their heads turn green. Sockeye can be anywhere from in length and weigh from . Two distinguishing features are their long, serrated gill rakers that range from 30 to 40 in number, and their lack of a spot on their tail or back. Sockeye salmon range as far south as the Columbia River in the eastern Pacific (although individuals have been spotted as far south as the 10 Mile River on the Mendocino Coast of California) and
Pain in fish that the absence of C-type fibres in cartilagenous sharks and rays indicates that signalling leading to pain perception is likely to be impossible, and the low numbers for bony fish (e.g. 5% for carp and trout) indicate this is also highly unlikely for these fish. Rose concludes there is little evidence that sharks and rays possess the nociceptors required to initiate pain detection in the brain, and that, while bony fish are able to unconsciously learn to avoid injurious stimuli, they are little more likely to experience conscious pain than sharks. A-delta-type fibres, believed to trigger avoidance reactions, are common