Arendt et at: Temporal trends and influences on fishery-independent catch rates for Caretta caretta in an important coastal foraging region 
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Figure 5 
Modeled catch (mean ±95% Cl) of loggerhead sea turtles (Caretta caretta ) 
per linear kilometer with respect to type of seafloor habitat during 4097 
coastal trawling events conducted between St. Augustine, Florida, (29.9°N) 
and Winyah Bay, South Carolina, (33.1°N) in 2000-2003, 2008-2009, 
and 2011. Seafloor type was classified as “hard” if >3 co-occurring 
indicator species were collected during the trawling event but classified 
as “probably hard” if only 1 or 2 indicator species were collected. The 
black line denotes overall catch rates. Bars denote the following 5-cm 
size classes of minimum straight-line carapace length: 55.1-60.0 (light 
gray); 60.1-65.0 (dark gray); 65.1-70.0 (white); 70.1-75.0 (medium gray); 
75.1-80.0 (charcoal). 
However, atypically high catch rates for this size class 
in 2000 were attributed to strong Gulf Stream intru- 
sion across the continental shelf (evidenced by large 
mats of the brown macroalgae Sargassum and “tar ball” 
deposits on South Carolina beaches; senior author, pers. 
observ.). Between 2003 and 2011, catch rates for this 
size class remained relatively stable; therefore, although 
we remain hopeful that this trend will persist, we urge 
attentive monitoring of catch rates for this size class 
as a high priority throughout the region through at 
least 2017. 
Even stable catch rates between 2000 and 2011 are 
encouraging for recovery of this species. Standardized 
catch rates (i.e., turtles per 30.5 net-hour) calculated 
by Maier et al. 4 for this study in 2003 (the year of the 
highest catch rates in this study) were 40 times greater 
than catch rates in coastal surveys in the South Atlan- 
4 Maier, P. P., A. L. Segars, M. D. Arendt, J. D. Whitaker, B. 
W. Stender, L. Parker, R. Vendetti, D. W. Owens, J. Quat- 
tro, and S. R. Murphy. 2004. Development of an index of 
sea turtle abundance based upon in-water sampling with 
trawl gear. Final Project Report to the National Marine 
Fisheries Service, National Oceanographic and Atmospheric 
Administration, grant no. NA07FL0499, 86 p. 
tic Bight (SAB) from 1950 to 1976 (Bullis and Drum- 
mond, 1978) and 13 times more than rates reported 
for the SAB shrimp fishery in the 1970s (Henwood 
and Stuntz, 1987). Although historical data sets were 
collected by fishery-dependent means versus fishery- 
independent means in this study, the magnitude of 
increases cannot solely be explained by subtle differ- 
ences in sampling gears or designs. Increased catch 
of loggerhead sea turtles also is reported elsewhere in 
this region (Ehrhart et al., 2007; Epperly et al., 2007; 
Arendt et al., 2012a), affirming historic increases in 
regional relative abundance of loggerhead sea turtles. 
The inability to detect a significant overall trend 
generated over a span of more than a decade illustrates 
the long-term commitment needed to assess relative 
abundance trends for long-lived species, as well as the 
importance of size-based assessments of such trends. 
The inability to detect significant trends also reflects 
autocorrelated increases in variance and catch rates. 
As the ratio of catch to noncatch changes significantly 
in a data set laden with zero values, data set variance 
also increases, thereby confounding the ability to detect 
trends, unless catch rates decrease with time. This re- 
lationship also occurs independently of whether catch 
rates increase as a result of true increases in popula- 
