Differential attraction does not seem related to either a temporal 

 summation of acoustic energy within a given band or, with reason, to 

 the pulse duration. Continuous signals, sounds having a single pulse, or 

 those having relatively long interval are rarely attractive. 



One study addressed the difficult problem of determining the biologi- 

 cal significance of acoustic stimuli in the predatory behavior of the lemon 

 shark (Banner, 1972). Similar field studies are encouraged for other 

 species, where possible. Efforts have also centered on determining those 

 variables within the acoustic stimulus itself, that sharks attend to, i.e., 

 particle displacement or associated functions (Banner, 1967), the frequency 

 spectrum (Myrberg et al . , 1969b and 1972) and pulse character and inter- 

 mittancy (Myrberg e_t a_l. , 1972; Nelson and Johnson, 1972). Such research 

 provides not only information on the acoustical modalities of sharks, but 

 also a method whereby free-ranging sharks can be brought to a specific 

 location for experimental purposes (e.g. Evans and Gilbert, 1971), as well 

 as for monitoring shark-shark and shark-diver interactions (e.g., Myrberg 

 et al., 1972). Recent findings have also suggested the possibility of 

 repulsion of certain species of sharks by acoustic means under specific 

 circumstances (Banner, 1972; Myrberg, 1974); this line of research should 

 be explored further. 



2) Chemical Stimuli 



Detection of and orientation to various chemical stimuli by sharks 

 have also been important subjects of study during the past decade (Bald- 

 ridge, 1966, 1969 a & b, 1971; Hobson, 1963; Hodgson, Mathewson and 

 Gilbert, 1967; Katsuki et al. , 1969; Kleerekoper, 1967; Tester, 1963). The 

 effectiveness of these stimuli in attracting sharks from a considerable 

 distance is directly related to water currents. As above, attractive 

 stimuli have been those which apparently represent wounded or distressed 

 prey. There has been little success in using chemical stimuli as repellents 

 as discussed in a later section of this report. Such repellents appear 

 generally ineffective in driving sharks from their prey, with one possible, 

 recently discovered, exception (Clark, 1974). Another recent study has 

 also shown two distinct ways in which sharks use olfaction to locate odor 

 sources (Hodgson and Mathewson, 1971). Yet, much remains to be learned. 

 Innovative studies of the chemical modalities of sharks deserve continued 

 support . 



3) Visual Stimuli 



Laboratory studies of vision in sharks have brought forth much informa- 

 tion about the capabilities of the modality (see next section), but field 

 work, to determine the role of vision in behavior of these animals is 

 virtually unknown (a few exceptions include studies by Johnson and McFadden, 

 1971 and Tester e_t a_l. , 1968). Yet, observed interactions among sharks, 

 such as threat and mutual interaction displays (Church, 1961; Johnson and 

 Nelson, 1973; Myrberg and Gruber, 1974) clearly indicate that vision is an 

 important modality in the lives of these animals. In feeding, for example, 

 vision is thought to direct the final approach of many sharks to prey 

 (Gilbert, 1966). Research directed at the functional significance of the 

 modality is badly needed, perhaps with focus on the use of models, reflected 

 images and other controlled stimuli. 



4) Electric Stimuli 



The ampullae of Lorenzini have been identified in the shark, 



10 



