Dressel and Norcross: Using poststrafication to improve abundance estimates from multispecies surveys 



487 



distribution of the other species may be a beneficial way 

 to make multiple uses of the data. Although the post- 

 stratified estimator may be biased, poststratification 

 may provide large gains in precision and a decrease 

 in bias in relation to an unstratified estimator. Large 

 increases in precision may be worth the acceptance of 

 some bias. 



Multispecies surveys are often not optimal for es- 

 timating the abundance of individual species but are 

 often necessary because of limited time and financial 

 resources. As a result, researchers need to explore al- 

 ternative sampling and analysis designs to increase 

 the precision of individual species abundance estimates 

 (NRC, 2000). Poststratification is a method that can be 

 applied to any number of species by using a wide range 

 of habitat and other variables that can be stratified. 

 Because of the dramatic increase in habitat information 

 that is likely to be collected in response to the expanded 

 emphasis in the Magnuson-Stevens Act (NRC, 2000) 

 and because of the adaptability of poststratification for 

 handling a multitude of types of data sets, the method 

 of poststratification may provide increased usefulness 

 for scientific researchers. 



Acknowledgments 



We thank Eric Munk and National Marine Fisheries 

 Service Kodiak Laboratory for the vessel and field assis- 

 tance from 1993 to 1996 and Bruce Short for field assis- 

 tance in 1991 and 1992. Additionally, we thank Brenda 

 Holladay, Franz Mueter, Brad Allen, Ed Roberts, and 

 Cindy VanDamm, who helped with the fieldwork for this 

 project, and Franz Mueter, Michael Simpkins, Robert 

 Foy, and Amy Blanchard for constructive advice. For 

 critical review of this article, we thank Milo Adkison, 

 Alison Banks, Allison Barns, Cathy Coon, Judy Ham- 

 ilton, Sue Hills, Heather Patterson, Andy Seitz, Dana 

 Thomas, Albert Tyler, and other anonymous review- 

 ers. This project was funded by Saltonstall-Kennedy 

 NOAA (contracts number NA16FD021601, NA26FD0156, 

 NA47FD0351), Minerals Management Service through 

 the University of Alaska Coastal Marine Institute (task 

 order numbers 11983, 12041, 18445), and the Rasmuson 

 Fisheries Research Council. 



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