Arendt et al.: Catch rates and demographics of Caretta caretta captured from the Charleston, South Carolina, shipping channel 
99 
Register, 2003). Consequently, loggerhead sea turtle 
cohorts during the past two decades have not uniformly 
benefited from TEDs. 
Concurrent with improving benefits from TEDs since 
the late 1980s, loggerhead nesting in Florida, where 
90% of loggerhead nesting in the Northwest Atlantic 
basin occurs, also increased between 1989 and 2000, 
after which a precipitous decline began (Witherington 
et ah, 2009). As such, it is reasonable to anticipate 
that strong cohorts hatched between 1989 and 2000 
should remain distinctly abundant given mandated use 
of appropriately sized TEDs in neritic habitats where 
these cohorts have likely occurred since 2003. Consis- 
tent with this assertion, statistically greater catches of 
small juvenile loggerheads were reported for estuarine 
habitats in North Carolina (Epperly et al., 2007) and 
Florida (Ehrhart et al., 2007) during the first decade of 
the 21 st century. However, given the smaller sizes as- 
sociated with loggerheads in estuaries (Lutcavage and 
Musick, 1985; Schmid, 1998) relative to coastal waters 
(Henwood, 1987; Schmid, 1995), loggerhead abundance 
in coastal habitats should also be monitored to evaluate 
the effectiveness of TEDs. 
In the southeastern United States, shipping channels 
have been extensively surveyed to assess sea turtle 
abundance (Butler et al., 1987; Henwood, 1987; Van Dol- 
ah and Maier, 1993). Continued studies to monitor log- 
gerhead abundance trends in shipping channels in the 
southeastern United States would provide some of the 
longest duration and most standardized observations for 
assessing temporal shifts in sea turtle distributions in 
this region. Because of their geographic configuration, 
commercial shipping channels throughout this region 
represent a “network of index in-water sites” that are 
ideal for long-term monitoring and for assessing de- 
mographic recovery criteria specified in the Northwest 
Atlantic Loggerhead Recovery Plan (NMFS and US- 
FWS, 2008). Therefore, long-term monitoring at these 
index sites with a fixed-location (i.e., Eularian) sam- 
pling design has great potential for assessing, with high 
statistical confidence, temporal changes in catch rates 
in the water relative to stranding rates in the same 
region at the same time (NMFS and USFWS, 2008). 
In order to gauge the utility of shipping channel data 
sets for monitoring regional loggerhead recovery ef- 
forts, we initiated a trawl survey in the Charleston, 
South Carolina, shipping channel (hereafter, “Charles- 
ton shipping channel”) in 2004. Baseline catch and 
demographic data were not as abundant as data from 
Port Canaveral, Florida, shipping channel (Henwood, 
1987), but they do date back to the early 1990s (Van 
Dolah and Maier, 1993; Dickerson et al. 1 ) when TED 
use was beginning to be required. Our first objective 
was to document catch and recapture rates relative to 
1 Dickerson, D. D., K. J. Reine, D. A. Nelson, and C. E. Dick- 
erson Jr. 1995. Assessment of sea turtle abundance in six 
South Atlantic U.S. Channels. U.S. Army Corps of Engineers 
Waterways Experiment Station Misc. Paper EL-95-5, 134 
p. U.S. Army Corps of Engineers, Vicksburg, MS. 
1991 (Van Dolah and Maier, 1993) and 1992 (Dicker- 
son et al. 1 ). The second objective was to document the 
demographic composition of loggerheads and compare 
the data to similar data collected in the early 1990s. 
Size-based sex and genetic assessments of loggerheads 
on foraging grounds (Braun-McNeill et al., 2007) are 
crucial for assessing whether loggerheads are likely to 
remain in the region upon reaching maturity (Sears 
et al., 1995; Encalada et al., 1998; Bowen et al., 2004; 
Roberts et al., 2005). As such, historical evaluation of 
these parameters is crucial for understanding what, if 
any, shifts in loggerhead foraging trends have occurred 
that may influence catch and recapture trends. 
Materials and methods 
Data collection 
Trawling was conducted within the Charleston, SC, 
shipping channel (32°42'N, -79°48'W) in three (A, B, 
and D) of four blocks and at seven (A1-A3, Bl, B3, Dl, 
D3, Fig. 1) of twelve index stations previously established 
by Van Dolah and Maier (1993). Five stations (B2, D2, 
E1-E3) sampled by Van Dolah and Maier (1993) were not 
repeated in 2004-07 owing to bottom obstructions that 
precluded safe and effective trawling. Trawling (2-10 
sea day cruises) occurred in May (2004-07), June (2004) 
and August (2004, 2005, 2007) with the same vessel as 
that used by Van Dolah and Maier (1993): the RV Lady 
Lisa, a 22.9-m trawler (except in May 2004 when the 
RV Georgia Bulldog, a 22.0 m trawler, was used). The 
sampling order of stations was randomly selected and 
stations were systematically sampled thereafter during 
2004-06; however, in 2007, two stations (B3, D3) with 
high catch rates in 2004-06 were targeted to expedite 
loggerhead collections for satellite telemetry studies 
(Arendt et al., in press). Trawling was conducted with 
standardized National Marine Fisheries Service (NMFS) 
turtle nets: paired 18.3-m (head rope), 4-seam, 4-legged, 
2-bridle nets; the net body consisted of a 10.2-cm bar 
and 20.3-cm stretch mesh, with tops and sides made 
of #36 twisted nylon and the net bottom of #84 braided 
nylon twine. Trawl bottom times ranged from six to 21 
minutes. 
Turtles were removed from nets and examined for 
general health status and injuries before being visually 
and electronically scanned for existing tags. Unique 
identification numbers were assigned to turtles when 
first encountered and subsequently re-used to denote 
recapture events. Body condition was evaluated and 
photographed before turtles were tagged externally 
with two Inconel 681 flipper tags (National Band and 
Tag Company, Newport, KY; distributed by the Archie 
Carr Center for Sea Turtle Research, Gainesville, FL) 
and internally with passive integrated transponder 
tags (TX1406L, 125 kHz, Biomark, Inc., Boise, ID). 
Standard morphometric data included five straight and 
six curved measurements and body mass; however, 
here we report only straight-line carapace length mea- 
