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Case Study - Dover Sole

Case Study - Dover Sole. Range from Baja California to the Bering Sea. On mud or muddy-sand, at 35 to 1400 m depths. Feed on polychaete worms, shrimp, brittle stars, and small bivalves. Winter spawning (December to February). Planktonic larval stage lasts at least one year.

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Case Study - Dover Sole

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  1. Case Study - Dover Sole • Range from Baja California to the Bering Sea. • On mud or muddy-sand, at 35 to 1400 m depths. • Feed on polychaete worms, shrimp, brittle stars, and small bivalves. • Winter spawning (December to February). • Planktonic larval stage lasts at least one year. • Gradual movement to deeper waters with growth. FW599 Winter 2008

  2. US West Coast Dover Sole - Landings FW599 Winter 2008

  3. Dover Sole – Sexual Dimorphism FW599 Winter 2008

  4. Dover Sole – Fishery Size Composition FW599 Winter 2008

  5. Dover Sole – Changes with Depth FW599 Winter 2008

  6. Dover Sole – Changes in Mean Weight FW599 Winter 2008

  7. Dover Sole – Small Fish are Discarded FW599 Winter 2008

  8. Dover Sole – Recent Discard Data FW599 Winter 2008

  9. Dover Sole - Assessment Data • Landings - 1910 to 2004 • Fishery length compositions - 1966 to 2004 • Fishery age compositions - 1981 to 2004 • Trawl logbook CPUE - 1978 to 1995 • Shelf survey biomass - 1980 to 2004 • Slope survey biomass - 1992 to 2004 • Survey length compositions • Observer Program discards - 2002 & 2003 FW599 Winter 2008

  10. Dover Sole - Assessment Model Structure • Two fisheries - South (CA+S.OR) & North. • Separate slope surveys - AFSC (1992 to 2001) and NWFSC (1998 to 2004). • Fixed size-retention functions - Early (to 1980); Late (1986 to 2004); and Transition. The fisheries now retain smaller fish. • Fixed maturity-at-size functions - Early (to 1954); Late (1985 to 2004); and Transition. Maturation now occurs at smaller sizes. • Natural mortality fixed at 0.09/yr. FW599 Winter 2008

  11. Dover Sole - Model Structure (continued) • Growth parameters estimated, but fixed relative variation (CV) in length-at-age. • Three periods for fishery selection L50s: Early (to 1979); Middle (to 1995); and Late. • Recruitment deviations from 1930. • Beverton & Holt stock-recruit curve with fixed steepness (0.8) and variability (0.35). • Reduced lambdas on length-at-age (0.1) and age composition (0.2) data. FW599 Winter 2008

  12. Dover Sole – Estimated Stock Trends Fishery Lengths Fishery Ages Shelf Survey Slope Survey Trawl Logbook CPUE Available Data FW599 Winter 2008

  13. Dover Sole – Fit to the Tuning Indices FW599 Winter 2008

  14. Dover Sole – Fit to the Length Compositions Southern Fishery Females Pearson Residuals (Black=Neg.) Males FW599 Winter 2008

  15. Dover Sole – Fit to the Age Compositions Southern Fishery Females Pearson Residuals (Black=Neg.) Males FW599 Winter 2008

  16. Dover Sole – Estimated Selection Curves FW599 Winter 2008

  17. Dover Sole – Likelihood Profile FW599 Winter 2008

  18. Dover Sole – Recruits versus Spawners FW599 Winter 2008

  19. Dover Sole – Random Starting Values FW599 Winter 2008

  20. Dover Sole – Retrospective Analysis Data through 2005 through 2004 through 2003 through 2002 through 2001 FW599 Winter 2008

  21. Dover Sole – Compared to Last Assessment FW599 Winter 2008

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