640 



Fishery Bulletin 91(4). 1993 



The results of these simulations, in particular the 

 results for five-boat fleets, and common dolphins, 

 strongly influenced subsequent regulations related to 

 comparability criteria for import of tuna caught by non- 

 U.S. fleets. These regulations now require that mor- 

 tality data for common dolphins be stratified separately 

 from all other stocks, and that non-U.S. fleets meet 

 the U.S. requirement for 100% observer coverage 6 . 



Of the three factors discussed here (dolphin group 

 type, percent coverage, and fleet size), only percent 

 coverage can be controlled by the sampling program. 

 Our results imply that providing maximum protection 

 for all dolphin groups would require mandating cover- 

 age to achieve a desired level of statistical precision 

 for the dolphin group type with the least statistically 

 stable data. 



Acknowledgments 



The U.S. fleet simulation study was designed by Bruce 

 Wahlen. Nancy Lo and Peter Perkins provided insight- 

 ful advice about sampling procedures and statistical 

 methods. We thank also the participants in the Work- 



6 U.S. regulations for acceptable levels of observer coverage for non- 

 U.S. fleets have progressed from a requirement for 33% coverage 

 of trips made by fleets with 10 or more vessels, 50% of trips on fleets 

 of 5-9 vessels, and 100% of fleets with 1-4 vessels during 1989 

 and 1990 (Federal Register 12/19/89;Vol. 54 #242, p. 51918-51923), 

 to 75^ of all trips regardless of fleet size during 1991 and 1992 

 (10/18/90; 55 FR 42235 and 10/8/91; 56 FR 50672), to the current 

 requirement for 100% coverage regardless of fleet size (Federal Reg- 

 ister 1/8/92; Vol. 57, #8, p. 668). 



shop on Estimating Dolphin Mortality, and two anony- 

 mous reviewers, who provided many useful comments 

 during the review process. 



Literature cited 



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1992. Status of dolphin stocks in the eastern tropical 

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1986. Incidental mortality of dolphins in the eastern 

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1980-1991. InterAmerican Tropical Tuna Commission, 

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