related sounds, whether purposeful or adventitious in nature, will become very 

 useful tools in monitoring activity patterns and occurrences upon the reef. 



An amplitude heirarchy of acoustical phenomena associated with the reef can be 

 erected if one resists the impulse to relegate sounds to discrete categories 

 and recognizes only that there is a continuum of sounds varying in the degree 

 of conspicuousness from nearly unnoticeable to deafening. Clicking and crack- 

 ling is pervasive and extremely audible at all times of the day. These sounds 

 are easily detectable by a diver's unaided ear. At night, the squirrelfish 

 staccatos and coos often rival the clicking and crackling but are generally of 

 inferior amplitude when heard from a distance of over 100 feet. Certain other 

 cyclical sounds, specifically the frog-like sounds, are audible at a moderate 

 distance from the source but tend to be more localized in nature and do not 

 possess the pervasiveness of the previously mentioned sounds. The degree of 

 pervasiveness of the sounds is likely a reflection of the population distribu- 

 tion of the sound producers on the reef. 



Sounds of a more individualized or singular nature tend not to be as conspicu- 

 ous as the more pervasive ones. Many, however, are easily detected by a diver 

 providing he is within a few meters of the source. Parrotfish, Trumpetfish, 

 and Surgeonfish crunches are particularly good examples of this as are Grouper 

 grunts. Spiny Lobster sounds and disturbances perpetrated by large predators 

 chasing prey. Other sounds appear to be generally detectable only with the aid 

 of electronic devices or upon extremely careful listening by the unaided diver. 

 Flutters associated with chase or escape of small fishes during aggressive 

 encounters, scrabbling sounds of deposit feeders such as goatfishes, purposeful 

 pops, quacks, and various other sounds produced by very small fishes living 

 under coral heads or in holes account for many of these nearly inaudible sounds. 

 Generally, in order to detect and record such sounds, the hydrophone must be 

 placed within a few feet of the source. 



The study of the bio-acoustical phenomena detected by us and their relationship 

 to the ecology and ethology of the coral reef community has just started. This 

 report represents only the first phase of analysis of the data collected during 

 the 20-day mission. We anticipate another year of analytical work before we 

 will have abstracted most of what is meaningful from the data collected during 

 that time. It is evident that in the future our experiments and data gathering 

 techniques will have to be carried out in a manner compatible with computerized 

 analysis . 



ACKNOWLEDGEMENTS 



In addition to aid received directly from the TEKTITE II Program, support for 

 this project was supplied through the Texas A&M University Sea Grant Program, 

 Texas A&M Organized Fund, and the Office of Naval Research. 



VI-105 



