NOTE Campbell et al ' Tag-reporting rates of commercial shrimpers in Texas bays 



623 



Brown Shrimp 



f?300 



0) 200 



50 60 70 80 90 100 110 120 130 140 150 160 170 180 



Total Length (mm) 



White Shrimp 



50 60 70 80 90 100 110 120 130 140 150 160 170 180 



Total Length (mm) 



Figure 2 



Length-frequency histograms of brown shrimp and white 

 shrimp measured in commercial catches, and of tagged shrimp 

 surreptitiously placed aboard boats in Aransas Bay, May- 

 November 1984. 



to promote the return of tags. Rawstron (1971) deter- 

 mined that some reward tags in his fish-tagging study 

 were not returned, but beheved that this number was 

 negligible. Likewise, Kutkuhn (1966) assumed low non- 

 reporting rates for reward tags. Published estimates 

 of tag-return rates for fish generally have ranged 

 between 55 and 65%, with rewards. Green et al. (1983) 

 reported much lower return rates by saltwater recrea- 

 tional anglers (29%) than had previously been esti- 

 mated, and that rates differed among species and 

 areas. Therefore, even with rewards, complete or high 

 reporting rates cannot be assured. 



Previous studies have relied on public-information 

 dissemination plans to achieve high reporting rates of 

 reward and non-reward tags. Matlock (1981) found that 

 83% (n 102) of the anglers not reporting tags in their 

 catch knew about TPWD tagging programs, and that 

 78% of these anglers failed to find the tag. This sug- 

 gests that public-information programs cannot assure 

 high reporting rates. Even if fishermen are aware of 

 tagging programs, they may not report recaptured tags 

 if these programs have continued over a long period. 

 The shrimp fishery in Texas had been subjected to fre- 

 quent tagging experiments during the previous 10 

 years, and the shrimp fishermen's enthusiasm for 

 reporting tags may have decreased. However, there 

 are no data to examine this possibility. 



Tag-return rates can be affected by many factors. 

 Each tagging study that depends on volunteer tag 

 returns would be enhanced by a concurrent estimate 

 of non-reporting rates. This would improve estimates 

 developed from returned tags. For example, during the 

 tagging program conducted during the same period as 

 this study, there were 2% of 25,870 released tagged 

 shrimp returned (Peng Chai, TPWD, Austin, pers. 

 commun.). If the reporting rate had been assumed to 

 be 100% rather than the observed 19%, fishing mor- 

 tality would be overestimated about five times. 



shrimp were smaller than those in the commercial 

 catch, they may have been more difficult to detect and 

 hence, were reported at a lower rate than if they had 

 been similar in size to those in the commercial catch. 

 The overall reporting rate with these white shrimp ex- 

 cluded was 19% (95% CI, 13-26%) which is similar to 

 the reporting rate for brown shrimp (21%). Tagged and 

 untagged brown shrimp sizes were similar. 



Complete return of tags cannot be assumed even if 

 rewards are offered. All tags used in the present study 

 were potential reward tags ($50-500) inserted into the 

 shrimp and placed into unculled shrimp catches; 

 however, only 19% of these shrimp were reported. Past 

 studies have relied on the use of monetary incentives 



Acknowledgments 



We would like to thank each member of the TPWD 

 Harvest and Resource Monitoring programs, without 

 whose assistance this task could not have been accom- 

 plished. Thanks also go to the Texas Parks and Wildlife 

 Department Law Enforcement officers who accom- 

 panied personnel into the bays and assisted in place- 

 ment of tagged shrimp on the commercial boats, and 

 also to the National Marine Fisheries Service for their 

 support. This study was funded by the Texas Parks and 

 Wildlife Department and by NMFS under P.L. 88-309 

 (Proj. 2-400-R). 



