larger than those encountered in the environment, was necessary before it would 

 produce a sound. In the environment, the stimulus eliciting sounds was quite 

 likely much more subtle, or the sounds may even have been spontaneous. There 

 are also reverberation, resonance and reflection phenomena associated with the 

 acoustical properties of the tank which may be significant. 



Quacks : 



Quack-like sounds have been detected from two apparent sources. That illus- 

 trated in Figures 6A, B, and 7A is produced by the Longspine Squirrelfish, 

 Flammeo mar i anus , while the other, to be discussed later, is of unknown origin. 



Each quack in Figure 6A consists basically of two pulses spaced ,0108 sec. 

 apart. The duality of pulses per quack is not evident in Figure 6A but is 

 shown quite well in Figure 7A, which is an analysis of the sounds played at 1/4 

 speed (1 7/8 inches/sec. rather than 7 1/2 inches/sec). Each pulse consists 

 of two predominant frequencies, approximately 800 Hz and 1200 Hz. It is appar- 

 ent in Figure 7A that the lower frequency components of each pulse persist 

 longer than the higher, and indeed those of the first pulse run over into the 

 second. Taken together, the two pulses of each quack span a time interval of 

 approximately .022 seconds. 



Because bimodal frequencies have been encountered often in other sounds recorded, 

 it is not likely that this in itself is responsible for the quack-like quality 

 of the sounds in question. Possibly, the duration of the low frequency compon- 

 ents and their apparent running together are responsible. It would be inter- 

 esting to duplicate individual components of the pulses involved and then put 

 them together on tape piece by piece until a quacking quality is produced. 



In Figure 6B, quacks 2 to 5 are accompanied by a series of single pulses of less 

 intensity spaced much farther apart temporally than the component pulses of the 

 quacks. Whether or not these pulses were produced by the same fish which pro- 

 duced the quacks is unclear. 



In addition to the quack-like sounds produced by the Longspine Squirrelfish, we 

 have detected similar sounds of unknown origin, although we suspect juvenile 

 Holocentrus . 



The sequence discussed here consists of 14 individual quacks. Figures 8A and 

 7B represent quacks 1 through 9 and 9 through 14 respectively. Quacks 1 and 11 

 are partly obscured by unrelated low frequency, high energy sounds. 



The time interval between quacks varies from .3 sec. between the first and 

 second to 1 sec. between the last two. There is a more or less steady increase 

 in the time interval between succeeding quacks as the sequence progresses. 



Each quack consists of a series of pulses which vary in number from 3 in the 

 first quack to 12 in the last. There is a general but not uniform increase in 

 the number of pulses per quack as the sequence progresses. For instance, 

 quacks 1 through 14 consist of the following numbers of pulses respectively: 

 3, 4, 4, 3, 4, 4, 3, 6, 9, 7, ?, 8, 7, 12. In most cases, the pulses were 

 separated by .013 sec. intervals. 



VI-92 



