Sanchez et al.: Patterns of courtship acoustics and spawning sites of Mycteroperca bonad 
193 
Table 4 
Geophysical parameters of spawning aggregations of black grouper at Mona Island (MI) and 
Bajo de Sico (BBS) in Puerto Rico. Deployment location of digital spectrogram recorders 
served as proxy for spawning aggregation site. An asterisk (*) indicates that the expected 
mean and standard deviation (SB) were calculated from sites that included a spawning ag¬ 
gregation of black grouper {Mycteroperca bonaci) seen in Table 1 in Kobara and Heyman 
( 2010 ). 
Promontory 
shape 
Promontory 
orientation 
Shelf edge 
depth (m) 
Distance 
to shelf 
edge(m) 
Distance to 
inflection 
point (m) 
Distance to 
100-m 
depth (m) 
MI 
Convex 
South 
27 
10 
24 
63 
BBS 
Convex 
West 
28 
19 
94 
233 
Mean* 
36 
25 
127 
59 
SB* 
10 
25 
94 
35 
(40%) of CASs were produced 1 h before sunset. It 
seems likely that courtship behavior, and presumably 
spawning, occurred mainly during the approaching 
low-light afternoons with no rising moon. This timing 
is shared by most large groupers in the western Atlan¬ 
tic (Colin at al., 1987; Sala et al., 2001; Scharer et al., 
2012b; Locascio and Burton, 2016). Evolution of dusk 
spawning has been suggested to control predation on 
both spawning adults and larvae for species that form 
transient spawning aggregations (Johannes, 1978; Co¬ 
lin and Clavijo, 1988). Evening spawning could provide 
an approximate 12-h period of darkness for dispersal of 
eggs away from the aggregation site. 
Tidal stage is directly related to moonrise. Begin¬ 
ning 9 DAFM, sunset coincides with the outgoing tide 
at Mona Island (NOAA Tides and Currents, website), 
increasing the likelihood that eggs are transported 
off the reef and away from egg predators (Johannes, 
1978). Along the western insular shelf of Puerto Rico, 
tidal currents are thought to play an important role in 
spawning timing for the red hind (Appeldoorn et al., 
in press), and tides have been shown to correlate with 
spawning timing in other locations (Johannes, 1978; 
Heppell et al, 2008). Although the effects of light and 
current are confounded within a single site, they are 
not confounded across sites. Unlike the conditions at 
Mona Island and Bajo de Sico, CAS peaks at Riley’s 
Hump did not coincide precisely with sunset hours but 
occurred slightly earlier. However, the exact time of 
spawning and the patterns of current flow at Riley’s 
Hump are not known, and current flows can be widely 
variable because of variations in the location of the 
Florida current. The significance of this offset and the 
relative effects of light and currents as factors control¬ 
ling spawning need further study. 
At Mona Island, black grouper aggregate around a 
specific geological feature. Whether this site is the ac¬ 
tual location of spawning or a part of a larger court¬ 
ship arena (Nemeth, 2012) is unknown. Dive surveys 
were not conducted in this study during early evening 
hours, the time at which spawning has been observed 
in Belize (Sala et al., 2001; Paz and Sedberry, 2008). 
However, the significant increases in CAS rates during 
the hours of dusk indicate that spawning was occur¬ 
ring, at least, nearby. This CAS pattern indicates that 
the aggregation forms within close proximity of the lo¬ 
cation of the DSG recorder—a conclusion that coincides 
with the morphometric analysis of nearby geological 
features (Table 4). 
The DSG recorder at Mona Island was deployed 10 
m from the shelf edge and sat at a depth of 30 m. Off 
the shelf edge, there is a step feature, where the bot¬ 
tom briefly levels out at 40 m before a second steep 
slope. Within 25 m of the DSG recorder is a promonto¬ 
ry along the shelf edge. All features are consistent with 
morphometric parameters of multispecies spawning ag¬ 
gregations in the Cayman Islands and Belize (Kobara 
and Heyman, 2008; 2010). These features are also com¬ 
mon to Bajo de Sico and indicate similar geophysical 
characteristics for ESA site selection. Although some 
variation exists within the geomorphology at spawning 
aggregations of black grouper (Paz and Sedberry 2008; 
Luckhurst, 2010), similar morphometric parameters 
have been observed for many documented FSAs, and 
these parameters can be used to potentially identify 
new FSAs (Kobara and Heyman, 2010). 
Transient FSAs provide an opportunity to survey 
the density and health of fish stocks for what are 
normally considered solitary species (Gannon, 2008; 
Luczkovitch et al., 2008). Including those in our 
study, only 4 spawning aggregations of black grou¬ 
per have been identified in U.S. territorial waters; 
the largest one is composed of only a couple hundred 
individuals (Eklund et al, 2000; Scharer et al., 2014; 
Locascio and Burton, 2016). However, population 
numbers indicate that black grouper must be spawn¬ 
ing at additional sites. Anecdotal evidence of eight 
additional spawning aggregations of black grouper in 
Puerto Rico, based on interviews with fisherman, sug¬ 
gests that many other sites must exist, although only 
