Sockeye salmon for courtship. If they waste too much energy, they might not be able to spawn. Males must also make the decision whether to invest energy in fighting for a female or for longevity on the spawning grounds. Aggressive behavior displayed by dominant males is predominantly directed towards intruding dominant males. Sometimes sockeye salmon males behave aggressively towards subordinate males. These encounters are short, with the intruding male leaving after one or two aggressive interactions. Spawning females direct their aggression primarily towards intruding females or other spawning females that are close by. However, they may also direct aggression towards intruding or
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