366 
All tape recordings were made with an Uher 
4000-S Report recorder and an Atlantic Re- 
search Corp. hydrophone (Model LC-57). Field 
recordings were carried out by securing a boat 
with three anchors over the reef area containing 
a school of fish. The hydrophone was placed 
inside a cave or under a ledge within 1 m of 
the fish and was secured with a weight. A small 
air-filled bottle was attached to the hydrophone 
cable about 1 m from the water surface to keep 
the cable taut and prevent entanglement in the 
reef. Field recordings were made at tape speeds 
of 2.3 cm/sec Q§ i.p.s.); laboratory recordings 
were made at 9.5 cm/sec (3f i.p.s.). 
Specimens 12-20 cm in total length were 
caught by hook and line or in traps and brought 
into the laboratory for study under more con- 
trolled conditions. They were established in 
groups of 6-7 fish in 756-liter fiberglass tanks 
with a plexiglas front, in which a "cave” was 
constructed with two building blocks covered 
with a piece of masonite (Fig. 1). Holes in 
the blocks allowed the fish to enter and leave 
through the side as well as through the front 
of the cave. A continuous flow of fresh sea 
TOP 
FRONT 
Fig. 1 . Top and front views of tank in which 
laboratory populations were maintained, showing out- 
side dimensions. 1 , Roof of cave; 2 , underwater 
speakers used in sound playbacks; 3 , building blocks 
with two holes through which fish could enter and 
leave the cave through the side as well as by the 
front opening; X, position of hydrophone. 
PACIFIC SCIENCE, Vol. XXI, July 1967 
water circulated through the tank at tempera- 
tures between 21° and 23° C. The hydrophone 
was suspended in front of the cave to record 
sounds. Behavior correlated with sound produc- 
tion was described immediately after recording 
the sounds. 
Sound playbacks were carried out. One under- 
water speaker (University MM-2L) was placed 
on each side of the cave. The sounds used for 
playbacks were all recorded from previous pop- 
ulations of M. berndti. They were played 
through one of the speakers from a continuous 
loop of tape on a Crown tape recorder (Model 
CR-25) which repeated the entire playback 
every 11 seconds. The response of four popu- 
lations to grunt, staccato, and knock sounds was 
determined. Each type of sound was played back 
once in a random order to each group of fish 
and at levels comparable to those emitted by 
the fish. The number of fish on the left or right 
side of the tank was determined every 15 sec- 
onds of a 5 -minute period with sounds played 
back during minutes 2 and 4 from one speaker, 
selected randomly. Recordings were made dur- 
ing the entire 5 -minute period to monitor play- 
backs and record any sounds produced by the 
fish. One observer (the recorder) noted the po- 
sition of the fish in the tank. Another, shielded 
from both the fish and the recorder, turned the 
sound on and off through one of the two speak- 
ers. The recorder had no prior knowledge of 
which speaker was being used during the test 
although the response of fish to certain sounds 
enabled him to determine the experimental 
speaker with 100% accuracy. 
Various species of fish commonly associated i 
with M. berndti in the field were introduced in 
a random order to seven individual populations, j 
These were: Myripristis berndti, M. argyromus, 'I 
Holocentrus xantherythrus, Priacanthus meeki, 
Parupeneus porphyreus, and Gymnothorax un- I 
dulatus. The type and number of sounds pro- !] 
duced by the populations were recorded for a 
1 -minute period before and during the intro- ] 
duction. 
Patterns of locomotory activity were deter- j 
mined for three fish, one for 24, one for 56, 
and one for 72 hours. The fish were placed , 
singly in a large doughnut-shaped chamber 7.6 
cm wide, 9.5 cm deep, and with a mean swim- j 
ming circumference of 87.6 cm. Fresh aerated 
