538 
Fishery Bulletin 115(4) 
Table 2 
Parameters and coefficients of determination (r 2 ) for models of capture metrics that predict 
blood biomarkers, lactate concentration, acidity (pH), and partial pressure of carbon dioxide 
(pC0 2 ), for blacktip sharks (Carcharhinus limbatus ) caught and released off Florida during 
2011-2013. Values are output of models, representing the equation for the line and the vari¬ 
ance accounted for. 
Intercept 
Fight 
time 
Handling 
time 
Temperature 
r 2 
Lactate 
-0.6020 
0.2092 
0.4660 
_ 
0.5758 
pH 
7.3377 
- 
-0.0150 
- 
0.1818 
pC0 2 
-7.3036 
-0.2358 
- 
0.5853 
0.1664 
Figure 2 
Significant relationships between blood biomarkers and capture metrics for blacktip sharks 
(Carcharhinus limbatus) caught and released between September 2011 and April 2013 at 
2 sites off Florida: Charlotte Harbor and surrounding waters in the Gulf of Mexico and off 
Cape Canaveral in the Atlantic Ocean. Open circles represent sharks that lived, and closed 
circles represent sharks that died, and lines of best fit were determined by the selected 
model. (A) Lactate concentration correlated with fight time and handling time, which is 
represented by the size of the data points. (B) Blood pH decreased with increasing handling 
times. (C) partial pressure of carbon dioxide (pC0 2 ) increased with increasing temperature. 
French et ah, 2015), and 12.5% for juvenile lemon 
sharks ( Negaprion brevirostris; Danylchuk et a!., 2014). 
Kneebone et al. (2013) found a lower mortality rate 
of 1.2% for juvenile sand tigers ( Carcharias taurus), 
whereas Heberer et al. (2010) found a rate of 26% for 
the common thresher shark (Alopias vulpinus). Howev¬ 
er, the feeding strategy of the common thresher shark 
is unique and mortality is highly dependent on the 
type of gear and fishing practice (mouth-hooked=0%, 
tail-hooked with trailing gear=66%; Sepulveda et al., 
2015). 
Our results were lower than many postrelease mor¬ 
tality rates observed for elasmobranchs captured by 
commercial fisheries: 24% for spiny dogfish ( Squalus 
acanthias ) in a trawl fishery (Mandelman and Far¬ 
rington, 2007); 15-31% for species captured on long- 
lines (Musyl et al., 2011; Marshall et al., 2015; Cam- 
pana et al., 2016); 43% for great hammerheads ( Sphyr- 
na mokarran) and 26% for bull sharks ( Carcharhinus 
leucas ) captured on drum lines (mortality estimated 
on the basis of the failure of satellite tags to transmit 
data; Gallagher et al., 2014); or 48% for released silky 
sharks ( Carcharhinus falciformis) captured in a purse 
siene (Poisson et al., 2014). In addition, we observed 
no at-vessel mortality, which can be as high as 88% for 
blacktip sharks caught by demersal longline (Morgan 
and Burgess, 2007). This finding suggests that the im¬ 
pact of recreational fishing is minimal, with a mortality 
rate <10%, and well below the 20% mortality threshold 
that is considered unacceptably high for recreational 
fisheries (Arlinghaus et ah, 2007). Although even low 
rates of postrelease mortality can be detrimental to a 
stock, depending on its life history and overall fishing 
pressure, results from a recent assessment suggest that 
