frequencies below 1000 Hz and attains a 30 decibel level at frequencies below 

 300 Hz. 



Frog Sound: 



Qualitatively, this sound, which on the basis of efforts during several night 

 dives we suspect emanates from H. ascensionis , is similar to the sustained 

 chorus of a single frog. It could also be compared to the frequent honking of 

 a small bulb horn similar to those used on bicycles. 



The individual pulses comprising the "honks" or "croaks" (Figure lOA) are bi- 

 modal where energy expenditure is concerned possessing peaks at 400 and 700 Hz. 

 The modes are more discrete than the two modes of the staccato sound apparently 

 produced by the same fish. In other words, the amplitude falls off faster up 

 and down the frequency scale from the peaks in the frog sound than in the stac- 

 cato. The lower frequency peak appears to be the stronger of the two and in 

 three instances rises 24 db above the background. The staccato sound repre- 

 sented at the end of the frog sequence demonstrates a definite similarity to 

 the frog sound in structure but differs as pointed out above and also in the 

 fact that the amplitude modes are slightly higher in frequency. In addition, 

 the individual pulses of the staccato are of shorter duration and are grouped 

 together whereas those of the frog sound are solitary. 



The bimodal frog sounds in some cases, viz., sounds 3 and 4, show a preliminary 

 short pulse at about 400 Hz. Whether this is truly a part of the sound or a 

 coincidental occurrence is not yet clear. 



Grunts : 



Figure lOB represents a series of 10 grunts produced by a Nassau Grouper, 

 Epinephelus striatus , which had been disturbed and was in the process of flight. 

 After the 10th, the grunts seem to degenerate into a sequence of staccato-like 

 sounds of lower intensity. The grunts are simple, possessing a single energy 

 peak at 200 Hz. They are strong sounds rising 42 db or more above quietest 

 background. 



Preceding and following the gi _ .ting sequence, bubble noises from the experi- 

 menting diver are apparent, as is the scrape of the diver's hand contacting the 

 substrate when startling the grouper. 



Rasps : 



The Spiny Lobster, Panulirus argus , frequents the reefs and isolated coral heads 

 in the vicinity of the habitat. Although the lobster is known to produce rasp- 

 ing sounds when disturbed, we did not attempt to audition the species during our 

 mission due to possible interference with another study in progress at the time. 

 Later, however, in the Florida Keys, we did obtain recordings of the distress 

 sounds while operating from a 14 ft. skiff near Hen and Chickens Reef. 



The frequency range of these squeaking rasps is quite wide, extending from below 

 80 Hz to above 10,000 Hz. The maximum energy expenditure (Figure IIB) is at 

 the low frequencies, below 500 Hz, and tapers gradually up scale. The rasps 

 are composed of a variable number of discrete pulses. In Figure llA the three 



VI -98 



