540 
Fishery Bulletin 115(4) 
S6 
• • 
SIS SI 
• • • 
24 
SI 
25 
26 27 28 
Temperature (°C) 
29 
30 
•• 
SS SI 8 
»• • mm 
5.0 
5.5 6.0 6.5 
Dissolved oxygen (mg/L) 
7.0 
• • • • • 
• • • • 
SI 
SI 8 
10 
15 
20 
Fight time (min) 
SS 
• • • • •• mmm 
si 
sis 
6 8 
Lactate (mmol/L) 
10 
12 
SI 8 SI 
• • • • 
SS 
• • mm m mm m • 
7.0 
si 
7.1 
SS 
7.2 
pH 
7.3 
7.4 
SIS 
pC0 2 (mm Hg) 
10 
12 
Figure 4 
At-vessel capture metrics for all live (black circles) and dead (shark 
ID numbers) blacktip sharks (Carcharhinus limbatus ) caught and 
released off Florida between September 2011 and April 201. Sharks 
were labeled according to the shark ID number from Table 1. En¬ 
vironmental metrics were temperature and dissolved oxygen; the 
behavioral metric was fight time; and biochemical metrics were 
lactate concentration, acidity (pH), and partial pressure of carbon 
dioxide (pC0 2 ). 
PCL (cm) 
Figure 5 
The relationship between precaudal length 
(PCL) and recovery period, determined 
with a generalized linear model, for black- 
tip sharks (Carcharhinus limbatus) caught 
and released off Florida between Septem¬ 
ber 2011 and April 2013. The relationship 
is given by the equation 28.1 - (0.13xPCL) 
- (G.473xpC0 2 ). The average behavioral 
recovery period determined from all behav¬ 
ioral metrics was shorter with increasing 
shark length (coefficient of multiple deter¬ 
mination^.45). Error bars represent stan¬ 
dard error of the mean; however, only the 
means were used in the regression. 
and Farrington, 2007; Hyatt et al., 2012). Many studies 
have found significant differences in these physiologi¬ 
cal indicators between at-vessel moribund and healthy 
sharks and have used them to predict and extrapolate 
postrelease mortality. In general, the exhaustive exer¬ 
cise associated with rod and reel capture caused acid- 
base disruptions in blacktip sharks that increased in 
magnitude with increasing fight time (decreasing pH; 
Fig. 2). Concomitant rises in La - and pC0 2 indicate that 
acidemia was of both metabolic and respiratory origin, 
respectively (Fig. 2). Although these physiological per¬ 
turbations in acid-base status did not impact survivor¬ 
ship in most of the blacktip sharks sampled, 2 of the 
3 mortalities may be linked to these changes in blood 
chemistry. These 2 sharks were exposed to high water 
temperatures (>29°C) and long fight times (13 min), and 
exhibited the highest La - levels, which would indicate 
blood acidemia driven by metabolic acidosis. This result 
suggests that higher water temperatures exacerbate the 
stress response of blacktip sharks and could cause high¬ 
er levels of postrelease mortality if fight times are ex¬ 
tended. However, the third shark that died after release 
was not exposed to high water temperatures (25.8°C), 
had a relatively short fight time (5 min) and handling 
time (8 min), and was not experiencing acidemia as 
indicated by a relatively high pH and the fourth lowest 
La - level measured in this study (Fig. 4). This finding 
suggests that the disruption of acid-base homeostasis 
may not be the only cause of death after exposure to 
rod and reel angling. 
Previous studies have been able to predict postrelease 
mortality from blood biochemistry (Moyes et al., 2006; 
Renshaw et al., 2012); however, because of the small 
sample size, the low mortality rate, and high variabil¬ 
ity observed in blood gas values, we were unable to 
predict postrelease outcome from blood gas analytes. 
Furthermore, blood biomarkers did not correlate with 
observed behavioral recovery periods, although larger 
sharks did display shorter recovery periods. This re¬ 
duced recovery time could be due to the fact that larger 
individuals have a lower cost of transport (lower en¬ 
ergy requirement for recovery, e.g., Parsons, 1990). 
