SHARKS AND UNDERWATER SOUND 393 



needed before serious consideration could be given to the perplexing prob- 

 lem of far-field orientation by sharks. 



Clear confirmation of those results appeared shortly thereafter when, 

 fortunately, field experiments were again conducted on several species of 

 sharks frequenting the underwater television site of the Bimini (Bahamas) 

 Video-Acoustic Installation (Myrberg et al. 1969, Richard 1968) and other 

 locations in Bahamian and Florida waters (Banner 1968, Nelson et al. 1969). 

 These independent studies established that certain kinds of underwater 

 sound are highly attractive to various species of sharks and that such attrac- 

 tion can be initiated in the far-field. 



Generally, long periods of time must pass before results from field tests 

 can be reexamined by appropriate tests of confirmation. Fortunately this has 

 not been the case with this question even though tests have often involved 

 large, highly mobile animals. Various findings regarding the acoustic biology 

 of free-ranging sharks have been repeatedly confirmed by the independent 

 studies of Nelson and his coworkers, who used Pacific species (Nelson and 

 Johnson 1970, 1972; Nelson et al. 1969), and by those of our team, using 

 primarily Atlantic species (Banner 1968, 1972; Myrberg 1969, 1972; Myrberg 

 et al. 1969, 1972, 1975a, 1976). Such confirmation has assuredly posed 

 additional questions and hypotheses from knowledge only recently gained, 

 but it has been necessary, since the research has had implications regarding 

 human safety. 



SHARKS AND SOUNDS-A STORY WITH MANY IMPLICATIONS 



The story that has unfolded during the last few years regarding the effects of 

 sound on the behavior of sharks encompasses a wide variety of diverse yet 

 interrelated topics. They include biophysical and ecological considerations, 

 learning and orientation processes, and even neural events at the level of the 

 sensory receptors. To highlight the most interesting points, this part of the 

 report is divided into a number of sections, each centering on one topic. The 

 entire story, as we at present understand it, includes information extending 

 beyond what can be covered under a few arbitrarily chosen headings. There- 

 fore, where necessary, an attempt has been made to explain interrelation- 

 ships that bridge the topics covered. The first section deals with the types of 

 sharks that have been attracted to sound sources; the second and third 

 center on the physical factors that appear to be important or unimportant 

 for an acoustic attractant; the fourth highlights the behavior of sharks in the 

 vicinity of a sound source; the fifth deals with those qualities of sound that 

 apparently promote a response opposite to attraction, i.e., withdrawal; and 

 the last section centers on the perplexing problem of directional hearing in 

 sharks. 



The Species List for A ttraction 



All species of sharks that have been examined in the field (Table 1) have 

 been found to be attracted to specific types of synthesized sounds as well as 



