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Hz were attributed to the bicolor damselfish on the ba- 
sis of analysis of A/V recordings and comparison with 
descriptions of the acoustic signature and associated 
behavior of this species by Myrberg (1972). Sound pro- 
duction, termed chirping, is used in conjunction with 
short vertical ascents and dives, termed dipping, by 
males to attract females to nest sites. Lunar patterns 
in sound production were very similar to those pat- 
terns described for spawning by this species. Schmale 
(1981) reported that most spawning by bicolor dam- 
selfish occurred between the full moon and just after 
the first quarter moon — timing that corresponds to 
the onset and sustained period of sound production 
by bicolor damselfish that was recorded in our study. 
Sound production was sustained at high levels beyond 
the first quarter moon to about the time of the new 
moon and then decreased sharply. Hatching occurs for 
this species near the time of the new moon (Schmale, 
1981); therefore, the prolonged period of sound produc- 
tion that extended past the time of spawning is likely 
associated with nest guarding. The bicolor damselfish 
is among the most abundant pomacentrids reported in 
visual surveys made by divers at Riley’s Hump as part 
of our study. Other common pomacentrids at the study 
sites included the blue chromis ( Chromis cyanea) and 
purple reeffish (C. scotti), neither of which have been 
documented as sound producers, but it is a possibil- 
ity that they produce sounds given the common use of 
sound by this family. 
The seasonal and lunar timing of the sounds pro- 
duced at 500-800 Hz do overlap somewhat with the 
period of reproductive aggregation of mutton snapper 
at Riley’s Hump in May-July. However, on many oc- 
casions when videos of large schools of mutton snap- 
per were recorded by remote A/V systems, as well as 
video of courtship and spawning behavior (senior au- 
thor, unpubl. data), the call type of this species was not 
recorded coincidentally, and there is yet no published 
evidence of sound production by snappers. 
The potential of Riley’s Hump as a source of mut- 
ton snapper larvae for the Florida Keys and southeast- 
ern Florida was demonstrated by Domeier (2004). Its 
upstream location in the Florida Reef Tract positions 
Riley’s Hump as the starting point of a larval path- 
way that could populate downstream juvenile habitats 
throughout the Florida Keys and southeastern Florida. 
In addition to being a documented spawning aggrega- 
tion site for mutton snapper, Riley’s Hump is a loca- 
tion where divers have observed courtship behavior of 
permit ( Trachinatus falcatus), and it has been recorded 
with the use of A/V systems. The general geomorphol- 
ogy of Riley’s Hump is consistent with features of 
multispecies spawning aggregation sites described by 
Heyman and Kobara (2010). The results of this study 
provide additional documentation of the importance of 
Riley’s Hump as a multispecies spawning site and a 
possible source of larval recruits for populations of red 
hind, red grouper, and black grouper. 
Ault et al. (2008b) reported spawning potential ra- 
tios of 0.8% and 17.7% for black grouper and red grou- 
per in the Florida Keys, respectively. These values are 
far below the federally defined benchmark of 30% for 
sustainability of these species, especially for the black 
grouper. Although a managed species, the red hind is 
not currently targeted commercially in the southeast- 
ern United States but is targeted in the U.S. Carib- 
bean; this species was the focus of a stock assessment 
recently held by Southeast Data Assessment and Re- 
view (SEDAR 6 ). Estimates of spawning potential ratios 
for this species are unavailable. 
Results from this study indicate that at least 3 eco- 
nomically important grouper species use Riley’s Hump 
as a reproductive habitat, further indicating its impor- 
tance as part of a marine reserve and the need for con- 
tinued research to understand its significance on the 
recovery of fish populations in the southeastern United 
States. Sonic tagging of groupers at Riley’s Hump dur- 
ing the spawning season could provide useful informa- 
tion on whether they are resident or transient and on 
their geographic range, especially in regard to the re- 
serve boundaries and level of connectivity that may ex- 
ist among regional populations. For example, estimated 
mean home ranges of black grouper and red grouper 
in the Dry Tortugas were 1.44-7.72 km 2 ; a range of 
areas slightly smaller than that of Riley’s Hump and 
considerably smaller than the total area (206 km 2 ) of 
the TSER (Farmer and Ault, 2011). 
Remote monitoring of fish behavior with passive 
acoustics was especially effective for assessment of the 
use of spawning habitat in the deep water adjacent 
to the highest vertical relief associated with Riley’s 
Hump. Little is known about fish use of this deepwater 
habitat because most research has been conducted on 
the hump at depths <37 m. Black grouper, red grouper, 
and red hind all used site RHDW, and it was the pre- 
ferred site of red grouper and red hind during the 2012 
spawning season. Divers also reported that they saw 
a school of 50-100 cubera snapper ( Lutjanus cyanop- 
terus) during the dive to recover the acoustic recorder 
at site RHDW in July 2012. 
In addition to providing the first evidence of the use 
of Riley’s Hump by groupers for reproductive purposes, 
we provide evidence of the value of the use of passive 
acoustics for exploring long-term monitoring of habitat 
use by important sound-producing fish. Such efforts 
will continue to be useful for fishery biologists and 
ecologists but will require the skilled management of 
large data sets and additional work for the documenta- 
tion of sound production by other species. 
Acknowledgments 
This research was funded by a grant from the NOAA 
Coral Reef Conservation Program, project number 
20205-2010. Expert field assistance was provided by 
members of the NOAA Southeast Fisheries Science 
Center laboratories in Beaufort, North Carolina, and 
Miami, Florida; the National Ocean Service’s Center 
for Coastal Fisheries and Habitat Research in Beau- 
