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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.

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Presentation on theme: "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."— Presentation transcript:

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. FW599Winter 2008

2 US West Coast Dover Sole - Landings FW599Winter 2008

3 Dover Sole – Sexual Dimorphism FW599Winter 2008

4 Dover Sole – Fishery Size Composition FW599Winter 2008

5 Dover Sole – Changes with Depth FW599Winter 2008

6 Dover Sole – Changes in Mean Weight FW599Winter 2008

7 Dover Sole – Small Fish are Discarded FW599Winter 2008

8 Dover Sole – Recent Discard Data FW599Winter 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 FW599Winter 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. FW599Winter 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. FW599Winter 2008

12 Dover Sole – Estimated Stock Trends Available Data Fishery Lengths Fishery Ages Shelf Survey Slope Survey Trawl Logbook CPUE FW599Winter 2008

13 Dover Sole – Fit to the Tuning Indices FW599Winter 2008

14 Dover Sole – Fit to the Length Compositions Females Males Southern Fishery Pearson Residuals (Black=Neg.) FW599Winter 2008

15 Dover Sole – Fit to the Age Compositions Females Males Southern Fishery Pearson Residuals (Black=Neg.) FW599Winter 2008

16 Dover Sole – Estimated Selection Curves FW599Winter 2008

17 Dover Sole – Likelihood Profile FW599Winter 2008

18 Dover Sole – Recruits versus Spawners FW599Winter 2008

19 Dover Sole – Random Starting Values FW599Winter 2008

20 Dover Sole – Retrospective Analysis Data through 2005 through 2004 through 2003 through 2002 through 2001 FW599Winter 2008

21 Dover Sole – Compared to Last Assessment FW599Winter 2008


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