Sound Production in Triggerfishes — Salmon, Winn, and Sorgente 
15 
CHANGE IN PEAK SOUND 
(Db re 0.0002 qbar) FROM 
NORMAL FISH 
PRESSURE 
LEVEL OF 
i 
as 
UNILATERAL REMOVAL 
OF PECTORAL FIN 
RAYS 
BILATERAL REMOVAL 
OF PECTORAL FIN 
RAYS 
SMALL HOLE IN 
AIRBLADDER 
► ► 
► ► 
• • 
• • 
:: • 
► 
► 
► 
► 
• • 
• • 
VARIOUS AM0UNT8 
OF OAS REMOVED 
FROM AIRBLADDER 
i I 
K 5 
01 
i 
ro 
o 
cn 
L_ 
cn 
UNILATERAL REMOVAL 
OF PECTORAL FIN 
BILATERAL REMOVAL 
OF PECTORAL FIN 
"0 < 3 ? 
m m 
o 
HO 
unilateral removal 
OF PECTORAL 
FIN SPINE 
c r> 
O 
c: 
r~ 
c 
CO 
• • 
BILATERAL REMOVAL 
OF PECTORAL 
FIN SPINE 
cn 
"I T~ 
' o 
cn 
Fig. 3. The change in peak sound pressures of operated fish from those of normal animals after 
various operations on parts of the sound-producing mechanisms. The pectoral fin consisted of a proximal 
fleshy muscular base and a distal stout spine and some rays. No sounds were detected when bilateral re- 
moval also included the muscular base (see text). 
The effect of operations on sound durations 
of experimental fishes is shown in Table 2. In 
M. piceus and B. vetula, there was no significant 
change in sound durations of fish after unilateral 
removal of the pectoral fin rays or the spine, 
when compared with their own normal sounds. 
In R. rectangulus, operated fish tended to pro- 
duce sounds of shorter duration than did normal 
fish. In all species, there was considerable vari- 
ability in sound durations from normal and 
operated fish. 
Octave band analyses of the sounds produced 
by all species are shown in Table 3. Sounds 
produced by pectoral fin movements ranged 
from below 75 Hz to below 9600 Hz in all 
species except B. bursa. This species, which was 
smaller than all others (total length under 20 
cm), produced some sounds with measurable 
pressures above 9600 Hz. Most of the acoustic 
energy in other species was found between 150 
and 1200 Hz, but there was considerable intra- 
specific variation not only between fish but also 
in consecutive sounds produced by the same fish. 
Behavior Associated with Sound Production 
All species but B. capistratus were observed 
in the field. When approached by a diver, about 
half the fish swam away rapidly. Other fish 
showed quite different behavior (Fig. 4). They 
swam in irregular paths, sometimes in wide 
circles, and then stopped by a hole or ledge in 
the reef. When again approached, the fish might 
