Pollock Conservation Cooperative Research Center
2002 Awarded Research Projects
An examination of the maturation of walleye pollock in the eastern Bering Sea in relation temporal and spatial factors
Award: $92,491
Estimated completion: January 31, 2005
Abstract
The overall goal ofthis study is to estimate accurate maturity schedules for walleye pollock (Theragra chalcogramma) in the eastern Bering Sea for use in annual stock assessments. Maturation rate is the proportion offish that are mature at a specific age or length. Estimates of maturity are an integral part ofyield determination process, because they are used to estimate spawning stock biomass from which total allowable catches are derived. For example, in November 2001, NMFS projected the biomass ofage 3+ (mature and immature) pollock to be 9.8 million metric tons in 2002, but the female spawning biomass was estimated to be just 3.0 million metric tons. The difference between the two estimates is attributed to immature fish, and small errors in maturity rate can result in large errors in spawning biomass estimates. Smith (1981) conducted the original study ofpollock maturity nearly 25 years ago, and those results still form the basis for determining pollock spawning stock biomass. This project collects pollock maturity data from PCC-member vessels in the eastern Bering Sea in the winter (January-April) fishery in 2002 and 2003. Data will be analyzed for spatial and temporal patterns. Results will be compared with recent, unpublished data on pollock maturity collected by the National Marine Fisheries Service (NMFS) during winter hydroacoustic surveys. This project represents a unique collaborative effort between the University ofAlaska Fairbanks (UAF), PCC-member vessels, NMFS, and Resource Analysts International (Dr. Vidar Wespestad). The project directly relates to two PCC research priorities -fishery stock assessment and stock assessment models and correct estimation ofmaturity and spawning biomass are necessary to understand pollock stock dynamics. The original proposal, submitted to PCC in fall 2001, appears in Appendix 1.
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