562 SCHEVILL, BACKUS, AND HEKSEY [CHAP. 14 



sites of croaker (Micropogon undulatus) choruses caused them to cease for 

 periods of several minutes (Loye and Proudfoot, 1946). Moulton (1956) found 

 that he could incite sea-robins {Prionotus spp.) to call by projecting crudely 

 imitative sounds into the water, and suppress their calls by transmitting other 

 sounds. Ta Volga (1958) elicited positive reactions from both male and female 

 of the goby Bathygobius soporator in response to sounds similar to those which 

 the male emits during the courtship. These imitations included the roughly 

 similar sound of an unrelated species as well as purely artificial sounds including 

 the projection of a tape-recording of Tavolga's voice saying, "ugh-ugh". 

 Moulton's and Tavolga's observations thus indicate low discrimination by the 

 fishes in the particular situations with which these workers were dealing. 



11. Exploitation of Marine Animal Sounds by the Oceanographer 



Having identified patterns of sound-production with their animal sources, 

 the ways in which oceanographers can use this information in elucidating the 

 lives of soniferous animals and in probing still other problems seem limitless. 



Fish and Mowbray (1959), during studies of sound-production by Bahaman 

 fishes, suggested that the common toad-fish there (genus Opsanus) was a 

 species different from the known Atlantic kinds because its underwater sounds 

 were different. Taxonomic investigation employing the usual criteria confirms 

 this. 



A simple example of the type of problem that can be solved, once a sound is 

 identified with its source, is that of the local distribution of the sound-producing 

 animal. Thus Johnson and co-workers describe, through sound surveying, the 

 disposition of snapping shrimp in the Point Loma area of southern California. 

 (Johnson, Everest and Young, 1947 ; Johnson, 1948.) Such a study trans- 

 cends the immediate issue of the distribution of the soniferous animal itself. 

 The distribution of the sound determines the limits of the particular habitat in 

 which the animal lives and so may be used to ascertain the distribution of 

 silent species living in the same habitat or even the distribution of certain 

 physical parameters of which the habitat is composed. Thus to Johnson and co- 

 workers it seemed feasible to determine the distribution of certain commercial 

 sponges from the distribution of snapping shrimp noise. Furthermore, their 

 survey showed that maxima of sound pressure due to the shrimp fairly repre- 

 sented the distribution of hard bottom in the study area. Moulton (1958) has 

 had similar successes in a survey of the sounds of the squirrel-fish, Holocentrus 

 ascensionis, and the Nassau grouper, Epinephelus striatus, in the Bimini area. 



The more one learns about a certain sound the grander the investigation one 

 can pursue through it. During warm months in certain areas along the coast of 

 the mid- Atlantic states, loud choruses of sounds are observed which have been 

 attributed to the croaker, Micropogon undulatus, a species of drum in which, 

 as mentioned above, both sexes are soniferous (Dobrin, 1947 ; Loye and Proud- 

 foot, 1946; Johnson, 1948). Beyond its seasonal character both annual and 

 diurnal fluctuations in the sound have been noted. Moreover, a comparison of 



