SECT. 4] 



SOUND PRODUCTION BY MAitlNE ANIMALS 



551 



distant wind or surf. Recently Russian fishery biologists have recorded and 

 described sounds of this sort from schools of Trachurus trachurus and Atherina 

 hepsetus (Shishkova, 1956 and 1958 ; Tokarev, 1958). Shishkova (1958) describes 

 the sound of a moving school of T. trachurus as most intense in the band from 

 40 to 80 c/s, weaker in the band 100-320 c'/s, and beginning at 400 c/s growing 

 again in amplitude until the band 1600-4000 c/s is reached, when the sound 

 diminishes uniformly to the upper limit of the analysis at 16,000 c/s. 



Fig. 6 is the spectrogram of the swimming sound of a school of the anchovy, 

 Anchoviella choerostoma, from the unpublished data of James M. Moulton, and 

 shows the steady sound of the swimming school of several million individuals, 

 as well as the emphatic sudden veering of the entire school. 



What significance these sounds may have in the lives of the animals remains 

 to be seen. The possibilities of exploiting such sounds commercially is obvious. 



Fig. 6. Sound spectrogram of swimming sounds of a school of Anchoviella choerostoma, 

 showing the steady swimming motions against the low background, punctuated with 

 two sudden "by-the-flank" ("veering") motions. (By courtesy of J. M. Moulton.) 



Recently Japanese workers have experimented with the transmittal of the 

 swimming sounds of fish schools (of the yellowtail, Seriola quinqueradiata and 

 others) by sonobuoy from ocean sites to shoreside stations (Hashimoto, Nishi- 

 mura and Maniwa, 1960). Data from sonobuoys placed in fish traps showed a 

 positive correlation between the occurrence of sounds attributed to the swim- 

 ming yellowtails and the amount of the catch. The paper implies that sonobuoy 

 surveys would be useful in selecting sites for fish traps. 



Swimming sounds of other marine forms, such as cephalopods, turtles, 

 pinnipeds and cetaceans, have yet to be demonstrated. Nevertheless, it is 

 occasionally asserted that the "tail beat" of cetaceans is audible. As far as we 

 know, these assertions are founded upon uncritical reports by inexperienced 

 observers (cf. the authorities quoted by Fish, 1949, pp. 33-34). This is not to 

 say that such sounds may not yet be demonstrated, as in the case of certain 

 fishes described above ; it is just that, to our knowledge, the only adventitious 



