Campbell et al.: Release mortality in the fishery targeting Lutjanus campechanus 
295 
founded in this study with fishing sector because the 
only commercial study that was available exclusively 
used circle hooks and many recreational studies used 
a mixture of hooks and a variety of venting practices. 
Furthermore, few studies reported hook sizes, and it 
is likely that the incidence of gut hooking, which can 
significantly increase release mortality, is related to 
hook size because mouth gape limits the effectiveness 
of large hooks. Therefore, our ability to estimate an ef- 
fect of circle hooks separate from fishing sector, study 
type, and season may have been diminished. We do 
not think that circle hooks lack positive benefits; we 
simply may not have been able to detect them from 
the available studies, and we know little about the po- 
tential interactions of other variables with hook size. 
Nonetheless, substantial documentation indicates that 
there are positive benefits associated with circle hooks 
(Cooke and Suski, 2004). 
Conclusions 
There have been significant improvements in under- 
standing release mortality in general and particular- 
ly in the red snapper fishery. Despite the significant 
efforts of many researchers, fundamental biases still 
persist in the various approaches. Estimates from sur- 
face-release studies do not address long-term effects of 
barotrauma, do not account for predation, and rely on 
submergence ability as a proxy to calculate mortality 
rates. Delayed estimates have been hampered by small 
sample sizes, cost prohibitive designs, excessive han- 
dling, and failure to duplicate normal conditions when 
releasing fish. Venting results were contingent upon 
the timing aspect specific to the various methods being 
used (i.e., delayed and immediate timing of estimates). 
A focus on increasing sample sizes in acoustic-tag- 
ging surveys and continued improvement of tag-and- 
recapture models would be useful. Passive- and acous- 
tic-tagging appear to offer good solutions because they 
can measure both immediate and delayed components 
and fish handling biases can be minimized, particularly 
as technology improves and costs are brought down. 
Experiments in which impairment scaling is estimated 
and that include both immediate and delayed esti- 
mates also would be valuable for the further develop- 
ment of those relationships within models and poten- 
tial adjustment of historical estimates. Future surveys 
should include some, if not all, of the following proper- 
ties: quarterly sampling, appropriate range of depths, 
water temperature and thermocline data rather than 
seasonal categorization, tag-and-recapture modeling, 
and measurement of barotrauma and reflex responses. 
Acknowledgments 
The authors thank the SEDAR 33 Assessment Work- 
shop panel who provided critical evaluation of the 
methods. We also thank many of the authors of the 
studies examined for answering numerous questions 
and providing additional data. 
Literature cited 
Campbell, M. D., J. Tolan, R. Strauss, and S. L. Diamond. 
2010a. Relating angling-dependent fish impairment to 
immediate release mortality of red snapper (Lutjanus 
campechanus). Fish. Res. 106:64-70. 
Campbell, M. D., R. Patino, J. Tolan, R. Strauss, and S. L. 
Diamond. 
2010b. Sublethal effects of catch-and-release fishing: 
measuring capture stress, fish impairment, and preda- 
tion risk using a condition index. ICES J. Mar. Sci. 
67:513-521. 
Cooke, S. J., and C. D. Suski. 
2004. Are circle hooks effective tools for conserving 
freshwater and marine recreational catch and release 
fisheries? Aquat. Conserv.: Mar. Freshw. Ecosyst. 
14:299-326. 
Davis, M. W. 
2002. Key principles for understanding fish bycatch dis- 
card mortality. Can. J. Fish. Aquat. Sci. 59:1834-1843. 
2007. Simulated fishing experiments for predicting de- 
layed mortality rates using reflex impairment in re- 
strained fish. ICES J. Mar. Sci. 64:1535-1542. 
2010. Fish stress and mortality can be predicted using 
reflex impairment. Fish Fish. 11:1—11. 
Davis, M. W., B. L. Olla, and C. B. Schreck. 
2001. Stress induced by hooking, net towing, elevated 
sea water temperature and air in sablefish: lack of con- 
cordance between mortality and physiological measures 
of stress. J. Fish Biol. 58:1-15. 
Davis, M. W., and M. L. Ottmar. 
2006. Wounding and reflex impairment may be predic- 
tors for mortality in discarded or escaped fish. Fish. 
Res. 82:1-6. 
Diamond, S. L., and M. D. Campbell. 
2009. Linking “sink or swim” indicators to delayed mor- 
tality in red snapper by using a condition index. Mar. 
Coast. Fish. 1:107-120. 
Dorf, B. A. 
2003. Red snapper discards in Texas coastal waters — a 
fishery dependent onboard survey of recreational head 
boat discards and landings. Am. Fish. Soc. Symp. 
36:155-166. 
Gitschlag, G. R., and M. L. Renaud. 
1994. Field experiments on survival rates of caged 
and released red snapper. N. Am. J. Fish. Manage. 
14:131-136. 
Hannah, R. W., P. S. Rankin, and M. T. Blume. 
2012. Use of a novel cage system to measure postrecom- 
pression survival of northeast Pacific rockfish. Mar. 
Coast. Fish. 4:46-56. 
Hannah, R. W., P. S. Rankin, A. N. Penny, and S. J. Parker. 
2008. Physical model of the development of external 
signs of barotrauma in Pacific rockfish. Aquat. Biol. 
3:291-296. 
Harrington, J. M., R. A. Myers, and A. A. Rosenberg. 
2005. Wasted fishery resources: discarded by-catch in the 
USA. Fish Fish. 6:350-361. 
