Our most effective acoustical monitoring device was the habitat based Sony 630-D 

 tape deck. Figure IB illustrates the stationary recording system consisting of 

 a Sony 630-D tape deck, time switch, two 500 ft. lengths of single conductor 

 shielded cable type Rg 59 A/u, two Atlantic Research LC-10 hydrophones, two 24 

 volt D.C. amplifiers powered by 12 volt dry cell batteries, stereo earphones, 

 and an amplifier with speaker. 



A3' X 2' X 1%' cage of %" mesh hardware cloth was used to impound live speci- 

 mens for detailed monitoring purposes. The cage was located on the sand flat 

 east of the habitat. 



Spectral analyses of recorded sounds were performed on a Kay Electric Company, 

 Model 7030-A, vibralyzer with a Model 6070-A contour display unit. 



PROCEDURE 



Our efforts during Mission 4-50 involved observation, monitoring and recording 

 at 17 stations (Figure 2) in the vicinity of the habitat, plus observation and 

 recording at various locations upon the reef using the portable recorder. The 

 portable Sony TC-110 cassette recorder proved useful in recording sounds pro- 

 duced by fishes of tenacious territorial habits; however, it did not provide us 

 with the degree of mobility we had expected, primarily because when we pursued 

 potential subjects with it, we quickly found that their tendencies to produce 

 sounds were greatly reduced or destroyed. Most effective use of this and our 

 other instruments was made in conjunction with extended periods of quiet obser- 

 vation at one location. It is unfortunate that on June 11 the portable unit, 

 but not the camera, was lost due to careless placement and an exceptionally 

 strong current running in a southeasterly direction in one of the channels 

 separating the northern and southern portions of the reef. 



The habitat based Sony 630-D tape deck was our most effective acoustical mon- 

 itoring device. This system enabled us to monitor and record sounds from two 

 stations simultaneously. The technique of recording and observing involved use 

 of a time switch which automatically turned the recorder on for 3 or 5 minutes 

 each hour. On the occasions when we left the habitat to observe the subjects 

 at the station being monitored, the recorder was customarily run continuously. 

 During these observation periods, the divers pinpointed events on the record- 

 ings by simply tapping code on clipboards. This practice did not seem to 

 appreciably alter the behavior of the organisms observed and provided a later 

 reference by which our observations could be correlated in time with the 

 recordings. 



The wire cage was used to impound five individuals, three Longjaw Squirrelf ishes, 

 Holocentrus ascensionis , and two Smooth Trunkf ishes, Lactophrys triqueter . They 

 were monitored for a period of three days in an attempt to detect a sound we had 

 designated "frog chorus." Although H. ascensionis is known to be a loquacious 

 sound producer, and relatives of Lactophrys have been implicated in frog-like 

 sound production in the past, we detected only a few weak staccatos during the 

 monitoring period. Normally, we would have expected three H. ascensionis to 

 produce a great deal of noise. The absence of significant sound production 

 by either species indicates the inhibitory effect confinement apparently has on 

 expression of normal behavior, when confinement is carried out in the organism's 



VI-84 



