Aucoin et al.: An underwater tool to catch and release Ginglymostoma cirratum 
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A 
Figure 2 
Images of (A) the poker-and-hook gear used to capture 
nurse sharks (Ginglymostoma cirratum) in this study, 
(B) how the lead line or ganion is kept taut around the 
poker (line and rope awareness is critical to avoid diver 
entanglement), and (C) how the cable ties are threaded 
through the eye of the hook and the hole at the end 
of the poker and used to cinch the hook bend at the 
poker tip. 
als that we suspected were pregnant (64.8 kg, 66.0 kg; 
see Castro, 2000). Two more sharks were released into 
the ocean (14.2 kg, 32.0 kg) because we already had a 
number of similar-size individuals. We monitored the 
6 sharks in the canal by snorkeling when water clar¬ 
ity permitted, whereas the 3 sharks in the tank were 
observed daily (and with video footage) and fed every 
3-4 days. The 3 sharks released in the holding tank 
were then re-assessed after 23-24 days and the sharks 
in the canal were randomly recaptured and re-assessed 
between 9 and 42 days. All individuals were tagged with 
numbered plastic Rototags 1 (Dalton ID Systems Ltd., 
Henley-on-Thames, UK) on their dorsal fins (see Labour. 
2005), their weight and total length were recorded, and 
their hook wounds were photographed to scale. 
To standardize our evaluation of each hook wound, 
we first put a measuring tape next to the wound and 
photographed both the wound and tape together with 
the camera lens directly above the plane of the skin 
surface. We then quantified hook wounds by process¬ 
ing digital images in Adobe Photoshop CC, vers. 2015 
(Adobe Systems, Inc., San Jose, CA) to calculate the 
geometrical parameters of wound severity: wound area; 
circumference; and circularity by using the Photoshop 
ruler tool to measure pixel length to scale, and then 
manually outlining the wound margin with the po¬ 
lygonal lasso tool (Sedgewick, 2008). Recording the 4 
parameters of hook depth, wound area, circumference, 
and circularity provided baseline data on initial wound 
status. Because medical studies show that wound area 
and circumference correlate with wound volume (Mel- 
huish et al., 1994; Flanagan, 2003), we used SPSS 
Statistics, vers. 20.0.0 (IBM Corp., Armonk, NY) to 
examine wound area in relation to hook depth (as a 
proxy for wound volume) by applying an analysis of 
covariance (ANCOVA), with shark body size as the co¬ 
variate. To further examine hook injury, specifically, 
1 Mention of trade names or commercial companies is for iden¬ 
tification purposes only and does not imply endorsement by 
the National Marine Fisheries Service, NOAA. 
Illustration of the caudal peduncle (i.e., tail base) indicated by the gray ellipse, that was 
targeted with the poker-and-hook capture method for nurse sharks (Ginglymostoma cirra¬ 
tum). It is a modification of a public domain image from Evermann et al. (1900). Courtesy 
of the Freshwater and Marine Image Bank, Univ. Washington, Seattle, WA. 
