37 6 
PACIFIC SCIENCE, Vol. XXI, July 1967 
TABLE 5 
Summary of Aggressive Behavior and Associated Sound Production in Eight 
Laboratory Populations of Myripristis berndti 
POPULATION 
NUMBER 
DURATION 
OF 
RECORDINGS 
NUMBER OF 
AGGRESSIVE 
INTERACTIONS 
AGGRESSIVE FISH 
' 1 ; d , . ■ 
AGGRESSIVE BEHAVIOR WITH: 
LARGER 
SMALLER 
KNOCKS 
GROWLS 
NO SOUNDS 
1 
2 hours 
31 
23 
8 
24 
3 
6 
2 
3 hours 
28 
(no 
data) 
19 
0 
9 
3 
4 hours 
95 
82 
13 
77 
0 
18 
4 
3 hours 
51 
35 
15 
36 
1 
14 
5 
1 hour 
9 
(no 
data) 
5 
0 
4 
6 
3 hours 
34 
26 
8 
19 
1 
14 
7 
3 hours 
29 
22 
7 
18 
2 
9 
8 
2 hours 
20 
19 
1 
9 
2 
11 
cave. Some fish swam to the outside and briefly 
"investigated” the eel’s tail, then dashed back 
into the cave. There was no indication of mob- 
bing or aggressiveness toward the eel. 
Response to Sound Playbacks 
The number of fish on each side of the tank 
during sound-playback experiments is shown in 
Table 7. When sounds were not emitted, the 
fish distributed themselves throughout the area 
under the cave. In some instances the school 
tended to aggregate briefly on one or the other 
side of the cave during the experiment. This 
distribution continued when background noise 
inherent in all playbacks and knocking sounds 
were played back through one of the two 
speakers. A few fish briefly turned toward the 
experimental speaker during playbacks of 
knocking sounds. The response to a series of 
staccato and grunt sounds involved several be- 
havior patterns. Initially, all fish immediately 
turned to the sound source. Within 5-10 
seconds, they swam toward the speaker from 
which the sounds were being emitted. From 2 to 
5 fish moved out of the cave to this speaker and 
dashed rapidly back into the cave. There was a 
general increase in rate of swimming move- 
ments. No staccato or grunt sounds were 
produced by the populations during any play- 
backs. The response of one population to a 
single staccato sound, repeated every 1 1 seconds 
during minutes 2 and 4, was comparable to 
responses by other fish to a series of staccato 
sounds. A second population tested showed a 
less intense response although several individuals 
oriented and moved toward the sound source. 
DISCUSSION 
The ablation experiments demonstrated that 
sounds were produced by a pair of bilateral 
muscles and the air bladder. Removal of one 
of the muscles reduced sound pressures, par- 
ticularly in the lower frequencies (75-150 
cps). The interpulse intervals and mean num- 
ber of pulses per sound were comparable in 
TABLE 6 
Number of Grunt-Staccato Sounds Produced by Laboratory Populations of 
Myripristis berndti One Minute After Introductions of Other Fish 
POPULATION NUMBER 
FISH 1 
2 
3 
4 
5 
6 
7 
Holocentrus xantherythrus 
0-0 
0-0 
0-0 
0-0 
3-1 
Priacanthus meeki 
6-0 
7-0 
0-0 
0-0 
0-0 
Myripristis berndti 
0-0 
0-0 
0-0 
0-0 
0-0 
Myripristis argyromus 
0-0 
0-0 
0-0 
0-0 
0-0 
Parupeneus porphyreus 
0-0 
1-0 
0-0 
0-0 
0-0 
Gymnothorax undulatus 32-16 
19-8 
80-21 
36-20 
78-18 
43-28 
115-25 
