sounds in the center of the sonogram are composed of 2, 7, and 5 pulses each. 

 It is obvious that the time between pulses can be varied by the lobster, .02 

 sec. in one case and less than half that in others. The duration of each 

 sound is, therefore, dependent upon time between pulses and number of pulses 

 emitted. 



Adventitious Fish Sounds 



Crunches : 



Parrotfishes (Scaridae) , surgeonf ishes (Acanthuridae) , and a number of other 

 "grazing" fishes customarily produce crunching sounds in the process of biting 

 epifaunal organisms from the reefs or other hard surfaces. The sound analyzed 

 in Figures 12A and B is apparently due to the feeding activities of a parrot- 

 fish although we have not yet determined the specific differences in spectral 

 or temporal structure between such feeding sounds produced by various species 

 of fish. 



The crunches analyzed here are characterized by a relatively broader range of 

 component frequencies than the purposeful sounds discussed earlier. Most of 

 the acoustical energy, however, seems concentrated below 4000 Hz. A compara- 

 tively great amount of variation in the frequencies of maximum energy expendi- 

 ture between pulse components of the .15 second long crunches is apparent. 

 Each such pulse is likely a result of the momentary impact of the fishes teeth 

 upon the hard substrate across which they are being dragged. Such frequency 

 variations are, therefore, not unexpected in view of the irregular nature of 

 the substrate being scraped and the probable instantaneous variation in velocity 

 at which the teeth are traveling across the substrate from start to finish of 

 a crunch. It is likely also that at times during the scraping process certain 

 parts of the tooth complex are not even in contact with the substrate while 

 other parts are. All this results in the production of a series of irregularly 

 spaced pulses which vary considerably in frequency structure and result in 

 rather disorganized crunching sound. 



Swooshing Crunch: 



This sound, which also can be likened to the crack of a low calibre rifle, is a 

 result of the lunge of a Trumpetfish, Aulostomus maculatus , in an effort to 

 seize prey. This fish often drifts vertically, head down, over the reef, occa" 

 sionally lunging downward after small fish or crustaceans. The sound thus 

 produced is variable to some extent but basically as represented in Figure 13A. 

 The first of the two temporal components of this sound appears to be trimodal 

 with respect to energy expenditure with peaks at approximately 700 Hz, 300 Hz, 

 and below 40 Hz. This would imply a complex source for the sound involving 

 possibly three generating mechanisms. The 300 Hz mode rises 30 db or more above 

 quietest background. The second temporal pulse, which lends a ricochet-like 

 quality to the sound, is simpler, having only one amplitude maximum at around 

 500 Hz. 



Both pulses are somewhat obscrured ir. the 300 to 500 Hz range by noise emanating 

 from air compressors, blowers, pumps and other equipment associated with the 

 underwater habitat. 



VI-101 



