Sockeye salmon can also occur and can lead to interactive segregation, which is when species emphasize their differences in diet and habitat to avoid competition. Interspecific competition can affect the growth rates of the salmon if their access to resources is limited. The total registered fisheries harvest of the sockeye in 2010 was some 170,000 tonnes, of which 115,000 tonnes were from the United States and the rest was equally divided between Canada and Russia. This corresponds to some 65 million fish in all, and to some 19% of the harvest of all Pacific salmon species by weight. Commercial fishermen in Alaska
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