Kotwicki et al.: Variation in the distribution of Theragra chalcogramma 



585 



metric tons per annum and the exploitation rate is in 

 the range of 0.5 million metric tons (50-100% of the 

 total estimate). 



Ongoing climate changes may affect pollock distri- 

 bution between the U.S. and Russian EEZs. Stabeno 

 and Overland (2001) reported a shift toward an earlier 

 spring transition in the Bering Sea. This can affect 

 the starting time of pollock migrations and the length 

 of time fish spend in the Russian EEZ, increasing the 

 availability of fish to the Russian fleet. This situation 

 should encourage us to closely monitor changes in mi- 

 gration patterns of pollock in the Bering Sea. 



Significant bias or error variation may be caused by 

 the interaction of fish movement with survey protocol. 

 For even relatively low fish migration velocities (<0.5 

 m/s), bias in estimated fish biomass can be very large 

 (McAllister, 1998). Therefore, fish migration vectors 

 should be estimated to minimize the bias created by 

 not taking into account these migrations in biomass 

 estimates. 



Acknowledgments 



The authors thank Angie Greig and Jan Benson for an 

 introduction to ArcGIS and help with geospatial prob- 

 lems that occurred during analyses of data. We also want 

 to thank Kevin Bailey, Jerry Hoff, Jim Ianelli, Jay Orr, 

 David Somerton, Phyllis Stabeno, Gary Stauffer, Neal 

 Williamson, and three anonymous reviewers for discus- 

 sions and review of earlier versions of this manuscript. 



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