Campbell et al.: Release mortality in the fishery targeting Lut/anus campechanus 
291 
tantly, our meta-analysis indicates that 
those estimates are highly dependent on 
the frequency that fish were vented be- 
fore release (Fig. 4). The accuracy of sur- 
face-release estimates is tenuous because 
misclassification of fate after release of 
tagged fish can be high; therefore, signifi- 
cant investigation into the rate of misclas- 
sification is needed (Sauls, 2014). 
Alternatively, it is possible that com- 
mercial fishing gear and practices may 
contribute to elevated estimates of release 
mortality for that sector. In the commer- 
cial sector, either electric or hydraulic 
bandit-gears with multiple hooks rapidly 
retrieve fish from depth. Rapid ascent and 
increased catch rates potentially result in 
increased sorting, handling, and air-expo- 
sure times, all of which have been shown 
to increase release mortality (Davis, 2002). 
The commercial data set in this meta-anal- 
ysis may not be completely representative 
of that fishing sector, but the assessment 
process by rule is required to use the best 
available data to make decisions. 
Finally, results of our analysis did not 
change after the removal of the commer- 
cial data set (Tables 2 and 3), indicating 
that model outcomes and predictions were 
driven by the recreational estimates and 
likely are most representative of that sec- 
tor. Research clearly is needed to sort out 
true effects associated with commercial 
fishing from more general effects that are 
seen throughout the fishery and that are 
i.o - 
08 - • 
• • 
f -W- Delayed and nonventing 
• • -V- Immediate and venting 
0.0 - * -R Immediate and nonventing 
— i 1 1 1 1 1 — 
0 20 40 60 80 100 
Depth (m) 
Figure 4 
Predicted relationship between depth and release mortality (propor- 
tion) of red snapper ( Lutjanus campechanus) in the Gulf of Mexico 
derived from the meta-analytical model for the interactions of im- 
mediate (dashed lines; seconds to minutes) and delayed (solid lines; 
hours to days) timing of mortality estimates with the venting (V) and 
nonventing (NV) treatments. Immediate estimates of release mortal- 
ity indicate that venting decreases mortality, but delayed estimates 
indicate that venting increases mortality. 
Table 3 
Model coefficients, standard errors of the mean, and 
P-values estimated in a meta-analysis of release mor- 
tality of red snapper ( Lutjanus campechanus ) in the 
Gulf of Mexico. This meta-analysis excluded the com- 
mercial data set. Significant coefficients are highlighted 
with asterisks (*** P<0.0001, ** PcO.001, * P<0.05), and 
“ns” indicates nonsignficant coefficients. 
Coefficient 
SE 
P 
Significance 
Intercept 
-1.782 
0.706 
0.0116 
* 
Depth 
0.0176 
0.0054 
0.0012 
** 
Timing 
0.5542 
0.688 
0.4205 
ns 
Venting 
0.6858 
0.6611 
0.2996 
ns 
Timing*Venting 
-1.4951 
0.7273 
0.0398 
Winter 
-0.9974 
0.2715 
0.0002 
*** 
Spring 
-0.7833 
0.2794 
0.0051 
** 
Fall 
-0.3397 
0.2287 
0.1375 
ns 
Annual 
-0.4132 
0.3446 
0.2305 
ns 
Hook type 
0.0023 
0.2054 
0.9912 
ns 
confounded by estimation methods (i.e., surface-release 
studies). 
The significant interaction between the immediate 
timing of estimates and venting treatments indicates 
that the effect of venting on rates of release mortality 
was dependent on the timing component inherently in- 
corporated into study-specific methods (i.e., surface-re- 
lease studies produce immediate estimates). Estimates 
were available most commonly from surface-release 
studies (Table 1; Fig. 1) and those are contingent on 
the assumption that failure of a fish to submerge is 
reflective of mortality (Campbell et ah, 2010a). Imme- 
diate estimates were significantly lower for the vent- 
ing treatment than for the nonventing treatment (Fig. 
4). For the delayed estimates (e.g., mortality estimates 
from caging studies), venting increased rates of release 
mortality — a finding that is congruent with results 
presented in a separate meta-analysis of venting from 
the same set of studies that produced delayed estimates 
(Wilde, 2009). Surface-release studies likely are too 
limited in scope to correctly evaluate the long-term ef- 
fects of venting on release mortality. Furthermore, sur- 
