336 
Fishery Bulletin 109(3) 
Table 5 
Correlation coefficients (r) and P-values calculated for chorus parameters determined for black drum ( Pogonias cromis ) from syn- 
optically recorded acoustic data at all study sites. Asterisks denote alpha values adjusted for experiment-wise error. PG=Punta 
Gorda, FL; CC = Cape Coral, FL. df=degrees of freedom. 
Chorus start time Chorus end time Chorus duration Time of max SPL 
Sites 
df 
r 
P 
df 
r 
P 
df 
r 
P 
df 
r 
P 
PG, CC1 
40 
-0.06 
0.71 
39 
0.31 
0.05 
40 
0.15 
0.35 
39 
0.21 
0.21 
PG, CC2 
40 
0.37 
*0.02 
40 
0.29 
0.07 
40 
0.41 
0.01 
40 
-0.08 
0.64 
PG, CC3 
38 
0.16 
0.34 
38 
0.32 
*0.05 
38 
0.26 
0.11 
38 
0.12 
0.48 
CC1, CC2 
42 
0.72 
<0.01 
42 
0.57 
<0.01 
42 
0.79 
<0.01 
42 
0.19 
0.24 
CC1, CC3 
39 
0.72 
<0.01 
39 
0.38 
0.02 
39 
0.52 
<0.01 
39 
-0.02 
0.91 
CC2, CC3 
39 
0.77 
<0.01 
39 
0.61 
<0.01 
39 
0.69 
<0.01 
39 
-0.10 
0.53 
same water temperature range regardless of latitude. 
In Chesapeake Bay for example, black drum spawn 
from late April through June (Wells and Jones, 2002) 
when water temperatures are within approximately 
the same range as that reported for the Gulf of Mexico 
during the spawning season (MDNR 2 ). Johnson (1978) 
estimated that black drum spawning at the mouth of 
Chesapeake Bay probably occurred in water tempera- 
tures of 15-21°C. Spawning by black drum later in 
the year at higher latitudes (June in Chesapeake Bay), 
but in the same water temperature range that occurs 
in Florida during February, indicates that tempera- 
ture may be more influential than photoperiod on black 
drum reproduction. 
Peters and McMichael (1990) noted that peak spawn- 
ing occurred around new and full moons and suggested 
this was due to increased tidal amplitude. We found 
no patterns in lunar periodicity associated with black 
drum sound production, but because the precise rela- 
tionship between the timing of sound production and 
spawning has not yet been explained for black drum, 
it is possible that these different behaviors may vary 
on lunar (or other) time scales. Associations with moon 
phase and fish sound production have been reported 
(Breder, 1968; Gilmore, 2003; Mann et al,. 2008). Aal- 
bers (2008) found increased that calling rates were 
associated with spawning by white seabass, which oc- 
curred throughout the lunar cycle but more so at the 
time of the new moon to four days after. 
Establishing chorus start and end times at two stan- 
dard deviations above mean daytime levels is a conser- 
vative approach for measuring chorus timing param- 
eters because the earliest and latest parts of the chorus 
are ignored. Still, there was sufficient variability in 
chorus duration over the course of the season to show 
the strong association between TAE and maximum 
SPL. Although TAE would appear to be a better choice 
to quantitatively represent nightly black drum sound 
production because it is a more comprehensive measure, 
2 MDNR (Maryland Department of Natural Resources), www. 
eyesonthebay.net, accessed Dec. 2009. 
maximum SPL has the advantage of not depending on 
the threshold level that is chosen, whereas TAE tends 
to increase at lower threshold levels. The correlation 
between maximum SPL and chorus duration was not 
as strong as that between maximum SPL and TAE be- 
cause threshold points from which chorus duration was 
measured did not account for variability in duration of 
signal amplitude above threshold as did the TAE cal- 
culation. In a previous study, we found a weak negative 
relationship between maximum SPL and chorus dura- 
tion of sand seatrout ( Cynoscion arenarius) (r=— 0.24) 
(Locascio and Mann, 2008). The relatively low correla- 
tion among C. arenarius data was because they were 
collected during peak spawning season when signal 
amplitude and chorus duration were consistently high 
and variability was low compared to the range that ex- 
ists when data are recorded across an entire spawning 
season as in this study (with P. cromis). 
Black drum exhibited a diel pattern of sound produc- 
tion consistent with general descriptions found in the 
literature for many fishes that produce sound associated 
with courtship and spawning. Calling levels increase 
rapidly within an hour or two before sunset and reach 
maximal levels within a few hours after dusk (Breder, 
1968; Mok and Gilmore, 1983; Luczkovich et al., 1999; 
Aalbers, 2008). In the previous hydrophone studies by 
Saucier and Baltz (1993) and Mok and Gilmore (1983), 
black drum calling was noted as early as 1300 and 1400 
h, respectively, and the majority of sound production 
occurred between 1800 and 2200 h. The earliest chorus 
start time in this study occurred at 1510 h on 19 Febru- 
ary 2005 at CC2, but individual calls were occasionally 
recorded throughout the day during peak season. 
Earlier chorus start times occurred during the peak 
spawning season and generally corresponded to later 
end times and higher maximum SPLs (Table 2). This 
pattern, along with later chorus start times at the be- 
ginning and end of the season, was responsible for the 
low r 2 from the regression with time of sunset for the 
two longer time series. Connaughton and Taylor (1995) 
discovered a similar pattern of high intensity calling 
earlier in the day that lasted later into the evening 
