Some Recent Observations on Acoustic Attraction of Pacific Reef Sharks.

Abstract : Responses of Pacific reef sharks to acoustic stimuli were observed at various times during a shark-research expedition to French Polynesia. Reef species exhibiting responses in a controlled sound playback experiment were: the gray reef shark, Carcharhinus amblyrhynchos; the blacktip reef shark, C. melanopterus; the silvertip shark, C. albimarginatus; and the reef whitetip shark, Triaenodon obesus. One pelagic shark, the oceanic whitetip, C. longimanus, was seen during acoustic playback. The playback experiment involved three test sounds (of 10/sec pulse rate): (1) 50 Hz sine wave, (2) 50 Hz resulted in clear attractions, based on numbers of sharks sighted and their behaviors. At other times attraction responses were observed to the following types of sounds: (1) speared, struggling fish; (2) hooked, struggling fish; (3) struggling fish in the mouth of a predator; (4) fish vocalizations; and (5) speargun-discharge sounds--the latter being a conditioned response observed at a site where native spearfishermen operate daily.