Arendt et al. : Temporal trends and influences on fishery-independent catch rates for Caretta caretta in an important coastal foraging region 
471 
fishery-independent catch rates that span one or more 
decades are also sparse, typically originate from spa- 
tially refined study locations, and are largely restricted 
to green ( Chelonia mydas) and loggerhead sea turtles 
in the South Pacific and NW Atlantic Oceans (Limpus 
et ah, 1992; Ehrhart et ah, 2007; Arendt et ah, 2012a). 
In addition to limited spatial context, localized sur- 
veys also tend to be conducted in sea turtle aggrega- 
tion areas where individuals exhibit site fidelity (Byles, 
1988; Avens et ah, 2003). Consequently, the statistical 
pitfalls attributed to monitoring fishery-dependent cap- 
ture rates in areas of resource concentration (Hilborn 
and Walters, 1992) also apply, and they necessitate the 
introduction of an element of randomization to reduce 
bias. For example, Epperly et ah (2007) randomly se- 
lected pound nets for monitoring sea turtle catch rates, 
and Arendt et ah (2012a) systematically sampled among 
spatial blocks to monitor sea turtle catch rates within 
a shipping channel. Although such practices improve 
statistical design, they are not as robust as truly ran- 
domized sampling. Excluding random selection of aerial 
survey transects (Epperly et ah, 1995a), which do not 
facilitate assessment of critical demographic parameters 
(Braun-McNeill et ah, 2007), data on sea turtle relative 
abundance from random sampling on foraging grounds 
over large spatial expanses are not available globally. 
To improve the random nature and spatial scope of 
in-water sea turtle data collected in the NW Atlan- 
tic Ocean, a trawl survey of sea turtle relative abun- 
dance was initiated in 2000 to address the need for 
“long-term, in-water indices of loggerhead abundance 
in coastal waters... to identify relative abundance of sea 
turtles over time, and to detect changes in size composi- 
tion with implications regarding recruitment” (TEWG, 
1998). Before mandated use of turtle excluder devices 
(TEDs), the decline of sea turtles in the NW Atlantic 
Ocean was attributed to the drowning of turtles during 
commercial shrimp trawling (NRC, 1990); therefore, 
sampling by trawling may seem odd as a sampling 
method. However, reduced tow times (Sasso and Ep- 
perly, 2006) enabled safe use of this accepted technique 
to capture sea turtles in turbid waters (Butler et ah, 
1987). For our study, we test the null hypotheses of no 
change in annual loggerhead capture rates in coastal 
waters from Winyah Bay, South Carolina, (33.1°N) to 
St. Augustine, Florida, (29.9°N) between 2000 and 2011 
overall (objective 1) and for prevalent 5-cm size classes 
(objective 2). We also test the null hypothesis of no 
significant influence of 26 parameters on capture rates 
(objective 3) with a generalized linear model, the most 
powerful linear model (Hilborn and Walters, 1992). 
Materials and methods 
Sampling and data collection 
For this study, sampling was conducted in coastal waters 
(at depths of 4.6-17.0 m) between Winyah Bay, South 
Carolina, and St. Augustine, Florida (Fig. 1). Four sub- 
regions were recognized on the basis of sampling strata 
established by the Southeastern Area Monitoring and 
Assessment Program (SEAMAP). The subregion that 
spanned from St. Augustine, Florida, to Brunswick, 
Georgia, for example, corresponded with sampling strata 
from the northern portions of SEAMAP strata 27-28 
to strata 34. SEAMAP strata 35 to 40 approximated 
the subregion from Brunswick to Savannah, Georgia. 
SEAMAP strata 41 to 46 and 47 to 50 corresponded with 
the subregions from Savannah, Gerogia, to Charleston, 
South Carolina, and from Charleston to Winyah Bay, 
South Carolina, respectively. Sampling began in mid- 
May, roughly 6 weeks after the seasonal return of log- 
gerhead sea turtles to nearshore coastal waters (Arendt 
et ah, 2012b). Sampling concluded in late July in all 
years except 2000, when sampling had to be extended 
into mid-August because of a temporary shutdown that 
occurred (in July) when we reached the initially permit- 
ted sea turtle catch limits authorized by the National 
Marine Fisheries Service (NMFS), Office of Protected 
Resources. 
At the start of each sampling year, a list of stations 
was randomly selected from a universe of 1500 coordi- 
nate pairs that represented the center of 3.4-km 2 grids 
of trawlable seafloor within the overall survey boundar- 
ies. Sampling was completed with 2-3 vessels, with a 
staggered north-to-south start, which primarily arose 
as a result of vessel availability. All vessels that par- 
ticipated in this study towed paired 18.3-m (head rope), 
4-seam, 4-legged, 2-bridle nets with a net body that 
consisted of a 10.2-cm bar and 20.3-cm stretch mesh. 
Subregion sampling alternated weekly to the north 
or south of vessel homeports to reduce spatiotemporal 
bias. Aboard each vessel, the daily order of station sam- 
pling alternated haphazardly between stations located 
roughly <6 km from shore and stations located >6 km 
from shore to diversify longitudinal sampling with re- 
spect to time of day and tide stage while still enabling 
a large (-100 km of latitude) area to be sampled by each 
vessel weekly. 
Captured sea turtles were removed from nets and ex- 
amined for general health and injuries. In the event of 
unconscious sea turtles, project staff had been trained 
in veterinarian- and NMFS-approved resuscitation 
protocols that involved manual ventilation by a self- 
refilling valve-bag apparatus. Sea turtles were scanned 
for pre-existing tags; if none were found, each sea turtle 
was assigned a unique identification number when it 
was first encountered (and the number was used again 
to denote recapture events). A suite of morphometric 
measurements were collected, but, here, we report on- 
ly minimum straight-line carapace length (SCLmin) 
measured with tree calipers. Sea turtles were tagged 
externally (2 Inconel 681 1 flipper tags, National Band 
and Tag Co., Newport, KY, purchased through the Ar- 
chie Carr Center for Sea Turtle Research, Gainesville, 
1 Mention of trade names or commercial companies is for 
identification purposes only and does not imply endorsement 
by the National Marine Fisheries Service, NOAA. 
