Whitney et al.: Mortality of Carcharhinus limbatus caught in the Florida recreational fishery 
539 
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Figure 3 
The differences in depth (black line) and dynamic acceleration (gray 
line) of the sway axis (tailbeats, measured in units of gravity [1 
g=9.8 m/s 2 ]) for (A) a blacktip shark (Carcharhinus limbatus), S16, 
that lived) and for the 3 sharks for which fatalities were observed 
(B) S18, (C) S6, and (D) SI. Sharks were designated as mortalities 
on a stationary depth, representative of the seafloor and a cessa¬ 
tion of consistent tailbeats. The final time that the shark landed on 
the seafloor was used to determine the time of death (dashed line). 
Sharks were caught and released off Florida between September 
2011 and April 2013. 
blacktip sharks in the Gulf of Mexico could sustain this 
level of mortality (SEDAR 6 ). 
Our mortality rate for blacktip sharks could be an 
underestimate because the sampling period was lim¬ 
ited to 3 days after release; any postrelease mortali¬ 
ties that happened after this period were missed. The 
3 gut-hooked animals may have been especially sus¬ 
ceptible to delayed mortality. Alternatively, the longer 
handling times required for blood sampling and tag at¬ 
tachment may have increased the likelihood of mortal¬ 
ity compared to standard fishing practices. However, 
we found that sharks behaviorally recovered within 
24 h and all mortalities occurred within the first 2 h, 
suggesting that most mortalities happen shortly after 
release. This is a common finding from past studies, 
where a single sharpnose shark mortality occured -40 
6 SEDAR (Southeast Data, Assessment, and Review). 2012. 
SEDAR 29 stock assessment report: HMS Gulf of Mexico 
blacktip shark, 142 p. SEDAR, North Charleston, South 
Carolina. [Available from website.] 
min after release (Gurshin and Szedlmayer, 
2004), and juvenile lemon shark mortalities 
occurred within a 15-min observation period 
(Danylchuk et al., 2014). Furthermore, for 
studies that have used longer-term pop¬ 
up satellite tags, mortality was reported 
to occur shortly after release: 87% of mor¬ 
talities happened within 60 min for dusky 
sharks (Carcharhinus obscurus ) and sand¬ 
bar sharks (Marshall et al., 2015); 100% of 
mortalities occurred within 4 h for common 
thresher sharks (Heberer et al., 2010); >50% 
for blue sharks (Prionace glauca ), shortfin 
makos, and porbeagles (Lamna nasus ) died 
within 6 h of release (Campana et al., 2016); 
and >50% of silky sharks died within 1 day 
of release (Hutchinson et al., 2015). 
Shark mortalities within 10 d of catch and 
release are largely attributed to capture-re¬ 
lated causes, yet the majority of mortalities 
that occur within the first 6 h after release 
are likely the result of the direct physi¬ 
ological stress of capture (e.g., blood acido¬ 
sis), or catastrophic hooking injuries (e.g., 
gill damage or puncture of the peritoneal 
cavity) (Epperly et al., 2012; Godin et al., 
2012; Renshaw et al., 2012; Kneebone et al., 
2013). This short time period is within the 
11 h postrelease recovery period measured 
in our study. Similar duration for behavioral 
recovery (based on tailbeat frequency) have 
been observed with juvenile scalloped ham¬ 
merheads (Sphyrna lewini) after tagging 
(Lowe, 2001). Furthermore, this behavioral 
recovery roughly corresponds with the du¬ 
ration of physiological recovery observed in 
captive sand tigers, whose blood biomarkers 
returned to baseline within 12 h (Kneebone 
et al., 2013). 
Some elasmobranchs appear to be able to recover 
from the physiological stress of capture relatively 
quickly (<1 d). However, differences in physiology, life 
history, and habitat preference indicate that these re¬ 
sults are species or population-specific, and managers 
should exercise caution before extrapolating such re¬ 
sults to other stocks (Mandelman and Skomal, 2009). 
For instance, Gallagher et al. (2017) recently used ac¬ 
celerometers to show that blacktip sharks fight more 
intensely than nurse sharks (Ginglyrnostoma cirra- 
tum) and tiger sharks (Galeocerdo cuuier ) upon being 
hooked, and this corresponded to higher La - values. 
Studies of blood chemistry of sharks have revealed 
that capture stress can manifest itself in changes in 
La - (Hoffmayer and Parsons, 2001; Moyes et al., 2006; 
Skomal, 2007; Hyatt et al., 2012), hematocrit (Brill et 
al., 2008; Marshall et al., 2012), HC0 3 (Skomal, 2007; 
Hyatt et al., 2012), K+ (Mandelman and Farrington, 
2007; Frick et al., 2010; Marshall et al., 2012), Ca 2+ , Na + 
(Marshall et al., 2012), and pH (Hoffmayer and Parsons, 
2001; Manire et al., 2001; Skomal, 2006; Mandelman 
