Locascio and Burton: A passive acoustic survey of fish sound production at Riley's Hump 
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2011 
Figure 7 
An example of sound production by longspine squirrelfish (Holocentrus rufus), measured in sound pressure 
levels (SPLs), from the time series of acoustic data recorded in the frequency range of 300-400 Hz at site 
RH1 at Riley’s Hump, Tortugas South Ecological Reserve, Florida Keys, in 2011. The seasonal period of 
sound production in this frequency range occurred from early spring through late summer and early fall, 
beyond the limits of the x-axis. Illustrated more closely in the inset figure, with bars that indicate periods 
of day and night, diel periodicity of sound production by this species is defined by a crepuscular pattern. No 
lunar periodicity is evident. Lunar symbols are defined as follows: new moon, #; first quarter, C>; full moon, 
O; and last quarter moon, 3. 
terns. This call type occurred at all sites between late 
March and mid-July and had an associated lunar pe- 
riod that began on or within 2 days of the full moon 
and continued to about the first quarter moon of the 
following lunar cycle, a period of approximately 18-20 
days. Nightly maximum SPLs associated with this call 
were about 25 dB above daytime background levels 
during peak season, and they increased rapidly just af- 
ter the full moon and decreased rapidly near the new 
moon (Fig. 8). The relatively high signal-to-noise ratio 
indicates that the source was close to the hydrophone. 
Discussion 
In this study, the common occurrence of sound produc- 
tion by red grouper, black grouper, red hind, longspine 
squirrelfish, and bicolor damselfish was documented 
at Riley’s Hump along, as well as the rare occurrence 
of sound production by yellowfin grouper and possible 
sound production by Nassau grouper. Several other rel- 
atively uncommon call types were recorded and noted 
during review of audio files and may be identified to 
source in future research. Temporal patterns in sound 
production by red grouper and red hind were similar 
to the patterns observed in analysis of previous record- 
ings made at sites in the Gulf of Mexico and Puerto 
Rico, patterns in which sound production was positive- 
ly correlated with spawning season (Mann et ah, 2010; 
Nelson et al., 2011). The last quarter lunar phase asso- 
ciated with maximum vocalizations of red hind in this 
study was consistent with the lunar period in sound 
production of red hind reported from the western coast 
of Puerto Rico (Rowell, et al,. 2012). The temporal asso- 
ciation of a lunar phase with aggregations of red hind 
has been shown previously to vary between sites. The 
significance of this finding is not well understood, but 
it may be associated with patterns in local currents 
(Nemeth, 2012). Patterns in lunar periodicities associ- 
ated with sound production by black grouper require 
more detailed analysis of time-series data and are the 
subject of a future study. 
In these prior studies, observations of grouper be- 
havior associated with sound production did not in- 
clude actual spawning; rather, they included courtship 
interactions and territorial behavior during which the 
presumed male was the sound producer. In our study, 
apparent courtship or territoriality between 2 black 
grouper was recorded on video, and one observation 
of similar behavior was made during a visual survey 
conducted on 19 January 2011 at site RH1. Because 
spawning is rarely observed, the exact timing and con- 
text of sound production in relation to gamete release 
is not well understood for grouper species, but sound 
production does generally correlate well with the re- 
productive period on a seasonal basis (Locascio and 
Mann, 2011a). 
In this study, more calls of red grouper and red hind 
were recorded over a longer seasonal period in 2012 
than in 2011. The more protracted period of sound pro- 
