Megamouth shark Baja California, Mexico, and samples taken from GenBank in order to perform a population genetic analyses of the megamouth shark; the results indicated no genetic diversity between populations found in different geographical locations, which indicates the species forms a single, highly migratory, interbreeding population. The first megamouth shark was captured on November 15, 1976, about 25 miles off the coast of Kāneohe, Hawaii, when it became entangled in the sea anchor of United States Navy ship "AFB-14". The species was identified as being of a new genus within the planktivorous shark species. Examination of the 4.5-m (14.7-ft), 750-kg (1,650-lb) specimen
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