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Fishery Bulletin 1 12(4) 
tous gas bladder (i.e., an air bladder not connected to 
the alimentary canal). 
Red snapper have been fished in the Gulf of Mexico 
(GOM) for more than a century and compose the most 
economically important fishery in this region (Strel- 
check and Hood, 2007). The first regulations managing 
the fishery were put in place in 1984 in response to 
the overfished status of the stock (for a comprehensive 
management history, see Hood et ah, 2007). In gener- 
al, management has focused on annual time closures 
and minimum-size regulations that have increased the 
number of regulatory discards, particularly in open- 
access recreational fisheries. Management of commer- 
cial fisheries has shifted recently to an annual catch 
share system, which removed the necessity to discard 
fish during seasonal closures but still does not elimi- 
nate regulatory discards if vessels do not possess catch 
shares or target other reef-associated species after an- 
nual catch shares are exhausted. 
The focus of management efforts has also shifted 
to regulations intended to reduce or minimize discard 
mortality. Regulations adopted in 2008 in the GOM, 
for example, require commercial and recreational fish- 
ermen to use circle hooks and to use a venting tool 
when catching reef fish. Venting tools are used to punc- 
ture and deflate the swim bladder after fish are rapidly 
retrieved as a means to mitigate the effects of baro- 
trauma. Recent research indicates that circle hooks 
are beneficial for reducing potentially fatal injuries for 
reef fish caught with hook-and-line gear, particularly 
for red snapper (Sauls and Ayala, 2012). A meta-anal- 
ysis of the relationship between venting practices and 
release mortality indicated negligible effects of vent- 
ing for red snapper (Wilde, 2009). In the Wilde (2009) 
meta-analysis, 1 experiment showed positive effects of 
venting on survival (Gitschlag and Renaud, 1994), 2 re- 
ports showed neutral results (Render and Wilson, 1994; 
Render and Wilson, 1996), and 1 experiment showed a 
negative effect (Burns et al. 1 ). 
Regulatory discards account for an increasing por- 
tion of total catch for managed reef fish in fisheries 
across the United States, and, in the U.S. GOM, the 
ratio of discards to landings for directed reef fish fish- 
eries was estimated at 41% (Harrington et al., 2005). 
The rate at which fish are discarded and quantification 
of their fate after release are crucial data needs for 
regional stock assessments in the GOM and south At- 
lantic. Because of the wide range in reported mortality 
rates (SEDAR 2 ; Campbell et al. 3 ) and the confounding 
1 Burns, K. M., C. C. Koenig, and F. C. Coleman. 2002. Eval- 
uation of multiple factors involved in release mortality of 
undersized red grouper, gag, red snapper and vermilion snap- 
per. Mote Marine Laboratory Technical Report 790, 53 p. 
[Available from Mote Marine Laboratory, 1600 Ken Thomp- 
son Pkwy., Sarasota, FL 34236.] 
2 SEDAR (Southeast Data, Assessment, and Review). 2005. 
Stock assessment report of SEDAR 7: Gulf of Mexico red 
snapper, 480 p. [Available from http://www.sefsc.noaa.gov/ 
sedar/.] 
3 Campbell, M. D., W. B. Driggers, and B. Sauls. 2012. Re- 
nature of the potential interacting factors, a compre- 
hensive evaluation of pertinent research is needed. 
Each method used to derive mortality estimates has 
its benefits, biases, and shortcomings that require ex- 
ploration; however, in general, problems are associated 
with the timing of observation, exclusion of predation, 
insufficient tag returns, sample size, and artifacts of 
experimental protocols (Campbell et al., 2010b). Meth- 
ods used to derive estimates in the red snapper fish- 
ery include surface-release observation, caging studies, 
hyperbaric-chamber simulations, acoustic tagging, and 
passive tagging (Table 1, Fig. 1). Mortality estimates 
from studies (Table 1) with the use of these methods 
are broadly categorized as either immediate (seconds 
to minutes) or delayed (hours to days) and refer to the 
time span over which the estimate is calculated. These 
different types of experiments and, therefore, differ- 
ent types of estimates are often treated as equivalents 
when used in an assessment. Although this aggregate 
approach is pragmatic, it may result in the use of 
imprecise estimates and introduce unexplored or un- 
known sources of bias. 
We present a meta-analytical approach with the in- 
tent of identifying critical issues and deriving a model 
of release mortality in the red snapper fishery of the 
GOM as a function of important covariates, such as 
depth, season, and capture gear. Meta-analytical meth- 
ods allow inclusion of all available point estimates, 
include a sample-size weighting scheme, and allow 
for the use of covariates in a mixed-effects modeling 
approach (Viechtbauer, 2010). The meta-analytical ap- 
proach was developed, and is useful, because it reduces 
the introduction of bias that hinders nonparametric ap- 
proaches often found in review papers (Sterne et al., 
2000; Nakagawa and Santos, 2012). 
Materials and methods 
Data used in this meta-analysis were compiled from 11 
studies that produced 75 distinct estimates of release 
mortality (Table 1). These studies represent everything 
the release mortality working group was aware of in 
2012 in preparation for the Southeast Data, Assess- 
ment, and Review (SEDAR) of Gulf of Mexico red snap- 
per, the SEDAR 31 stock assessment. The data work- 
shop portion of the SEDAR process typically consists of 
analysis by expert panelists and assessment biologists 
of data sources that potentially feed into stock assess- 
ment models (for further information about SEDAR, 
visit: http://www.sefsc.noaa.gov/sedar/). 
There are multiple estimates from some of the 11 
studies examined for this meta-analysis because they 
were conducted at multiple water depths or seasons. 
Most of the estimates were compiled from refereed pub- 
lease mortality in the red snapper fishery: a synopsis of three 
decades of research. SEDAR31-DW22, 25 p. [Available from 
http://www.sefsc.noaa.gov/sedar/.] 
