Spreading the effort to focus the analysis: otolith collection in the eastern Bering Sea

No abstracts are to be cited without prior reference to the author.

The Alaska Fisheries Science Center has conducted annual standardized resource surveys of the eastern Bering Sea continental shelf since 1982. In response to the need for agedata that were better suited for stock assessment and spatial analysis, a new procedure for collecting otoliths from walleye pollock was introduced in 2006. In prior years, a fixed number of otoliths per length per sex were collected from pollock within areas with different growth rates, and the resulting data were combined to create a single age-length key (ALK) for each sex. We performed a simulation to illustrate spatial artifacts caused by applying a combined ALK to areas of different growth rates. Artificial ontogenetic migration from the area of slower growth into the area of faster growth was created by systematic length-age conversion errors in the simulation. The procedure used for the collection of otoliths from pollock prior to 2006 shows a mismatch between the abundance of pollock and the number of otoliths collected, and it created periodic cessation of collecting common sizes while focusing on hunting for rare sizes. The new method for collecting pollock otoliths is random and spread evenly in space, allowing examination of the data for spatial patterns in age and length-at-age, and allowing construction of multiple ALKs representative of biological distributions rather than predetermined geographical boundaries.