420 



Fishery Bulletin 98(2) 



strata CPUE used in the estimator of absolute abun- 

 dance. Sediment distribution, however, is often very 

 patchy, and the exact area on the bottom of any type 

 of sediment is typically not known. Accurate map- 

 ping of bottom sediment is expensive and thus it 

 makes sediment-based stratification impractical. An 

 alternative approach for taking sediment into acco- 

 unt is to conduct a series of depletion experiments 

 at locations that are representative of the entire 

 survey area. If a sufficient number of experiments 

 are conducted, the effects of sediment on catching 

 efficiency will be accounted for. Although we agree 

 that efficient stratification is an important aspect 

 of designing cost-effective marine resource surveys, 

 we stress that careful estimation of sampling gear 

 efficiency through a series of depletion experiments 

 could significantly improve the accuracy of absolute 

 abundance estimates. Both elements are essential in 

 designing effective sample survey programs for esti- 

 mating vital characteristics of a population. 



Acknowledgments 



This project was funded by the National Oceanic and 

 Atmospheric Administration (NOAA) and Maryland 

 Department of Natural Resources. J. H. Volstad and 

 A. Sharov are grateful to B. Rothschild for providing 

 us the opportunity to work on this project. We thank 

 T. Maurer, E. Connor, and captains A. Moore and D. 

 Pierce for assisting with the field work in Maryland 

 waters. We thank R. Lipcius and M. Montain for 

 their research cooperation and for providing the data 

 from depletion experiments conducted in Virginia. 

 We greatly appreciate suggestions from two anony- 

 mous referees that helped improve the manuscript. 



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