Colura and Bumguardner: Effect of the salt box catch-bycatch separation procedure, as used by the Texas shrimp Industry 
409 
gression models for the variables M and initial survival of 
bycatch in experiments conducted with samples collected 
from the fishery. It also entered multiple regression models 
for the dependent variable M of bycatch and Atlantic croak- 
er in the control experiments. The use of the salt-box sig- 
nificantly reduced catch separation time in control experi- 
ments, suggesting that the use of the salt-box could possibly 
reduce M by speeding catch separation time. The impor- 
tance of reducing catch separation time has been corrobo- 
rated by Ross and Hokenson (1997) who reported a posi- 
tive correlation between mortality and on-deck sorting time 
for three species of bycatch (American plaice, Hippoglossoi- 
des platessoides\ witch flounder, Glyptocephalus cynoglos- 
sus; and pollock, Pollachius virens ) associated with the Gulf 
of Maine northern shrimp (. Pandalus borealis ) fishery. 
Trawling time was also an important variable affecting 
M and survival. It was correlated to M, initial survival, and 
final survival of bycatch and entered the final survival re- 
gression model for bycatch from the fishery. This variable 
may affect survival in several ways. Longer trawl times 
in general result in larger catches. This would presum- 
ably increase catch separation time thus contributing to 
increased bycatch mortality. Long trawl times would also 
increase the time bycatch is in the net, thus increasing the 
chance of fatal injuries. 
In the absence of a satisfactory method to reduce the catch 
of nontarget species, survival of bycatch could probably be 
improved by limiting the time a trawl is fished and by re- 
quiring the catch to be separated prior to resumption of fish- 
ing. These variables were the only ones found in our study 
that had significant impact on bycatch survival and that 
could easily be altered to improve survival. Enforcement of 
either of these proposals, however, would be difficult. 
Use of percent survival estimates at the conclusion of 
the observation periods in our study to predict long-term 
survival of bycatch released into the bay is not recom- 
mended. Stress in fishes is characterized by hypersecretion 
of epinephrine, norepinephrine, and corticosteroids. These 
hormones induce secondary effects resulting in changes 
in metabolism, osmoregulation, and the immune systems 
(Mazeaud et al., 1977) that last for several days and can re- 
sult in increased susceptibility to disease (Wedemeyer and 
McLeay, 1981). Furthermore, stress can lead to behavioral 
changes (Wedemeyer, 1974) that might make the fish more 
susceptible to predation. Specimens can be maintained un- 
der identical conditions (in the laboratory or field) to com- 
pare survival and mortality rates of individuals treated dif- 
ferently at capture. However, it would be speculative to 
project survival estimates of specimens maintained in any 
form of captivity to those released into the wild because it is 
impossible to account for predation and possibly disease. 
Acknowledgments 
We thank Captains Ted Bates Jr., Dennis Williams, and 
Bobby Pash for allowing us to board their boats and collect 
samples. We also thank TPW personnel Norman Boyd, 
Karen Meador, and Dennis Pridgen for their assistance in 
finding cooperating shrimpers; Eric Young, David Westbrook, 
Roberta Vickers, and Valentin Flores III for their assistance 
in sample collection; and Cynthia Gibbs for her assistance in 
manuscript preparation. Lastly, we thank Rocky Ward, Mark 
R. Fisher, Lawrence W. McEachron, Rebecca Hensley, Robin 
K. Riechers, David Abrego, and William J. Karel of TPW, 
and three anonymous reviewers for their critical review of 
the manuscript. This project was jointly funded by Texas 
Parks and Wildlife and the U. S. Department of Commerce, 
National Marine Fisheries Service, Marine Fisheries Initia- 
tive (MARFIN) award number NA57FF0047. 
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