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Re-Estimation of Biological Reference Points for New England Groundfish Stocks

Re-Estimation of Biological Reference Points for New England Groundfish Stocks. Terms of Reference Working Group Composition and Support Background to Re-Estimation Project Description of Working Group Procedures & Report Summary of Specific Results and Advice. Terms of Reference.

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Re-Estimation of Biological Reference Points for New England Groundfish Stocks

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  1. Re-Estimation of Biological Reference Points for New England Groundfish Stocks • Terms of Reference • Working Group Composition and Support • Background to Re-Estimation Project • Description of Working Group Procedures & Report • Summary of Specific Results and Advice

  2. Terms of Reference • assemble appropriate abundance, catch and other data for 19 stocks included in the Northeast Multispecies FMP • agree on appropriate methodology with which to estimate maximum long-term yield and associated biomass and fishing mortality rates • revise estimates of Bmsy and F msy (or proxies) as appropriate • project stock status through 2009 relative to long-term biomass targets and calculate maximum fishing mortality rates necessary to achieve targets (if possible) • comment on methods to estimate target mortality rates for rebuilt stocks that minimize probability stocks will fall below Bmsy in the future

  3. Working Group Composition • NEFSC Participants: • Dr. Jon Brodziak • Mr. Steve Cadrin • Dr. Chris Legault • Mr. Ralph Mayo • Dr. Steve Murawski - Chair • Ms. Loretta O’Brien • Dr. Bill Overholtz • Dr. Paul Rago • Dr. Fred Serchuk • Dr. Mike Sissenwine • Dr. Mark Terceiro • Ms. Susan Wigley • Outside Members: • Dr. Jim Armstrong NCDMF • Mr. Stratis Gavaris DGO-NB • Dr. Pamela Mace NMFS-O/S&T • Dr. Rick Methot NMFS-NWFSC • Dr. Grant Thompson NMFS-AKFSC • Dr. Doug Vaughan NMFS-SEFSC • Council Observers: • Mr. Tom Nies • Mr. Steve Correia (MDMF) • Experts in Reference Point Estimation • Experienced with NMFS SFA Guidelines (authors) • Expedited Process

  4. Background • New data available, especially documenting re-building of many stocks (important in determining conditions for re-building) • Some reference points inconsistently determined with assessment methods and data (e.g., some results from Overfishing Panel) • Surplus Production Models tend to Find Bmsy and Fmsy within the Range of observed data (even for chronically overfished stocks) (scallop example, haddock example) • Recommendations for multiple approaches applied to data sets (NRC Reviews) • Proxy reference points (survey biomass and exploitation indices) currently not linked to re-building schedules

  5. Biomass Reference Point OFD Committee : Average Recruitment * Biomass/recruit

  6. Groundfish Trawl Mesh – 1952 (by H. Graham)

  7. Procedures and Report • 4 Primary Methods Used to Estimate Bmsy & Fmsy • “Parametric” Stock-Recruitment Models • “Non-Parametric Empirical” Approach • Surplus Production Models (ASPIC) • Index-Based Methods • Up to 24 different parametric functional forms fit to S-R Data • selection criteria developed • Curved relationships considered but not without mechanism • Compared with non-parametric approach • Non-parametric approach applied BPR * some statistical moment of the recruitment distribution (mean, median, quartiles…) • Surplus production estimates from SARC 33 Reviewed for GB Winter Flounder & White Hake – Accepted • New Index Methods developed and tested (Replacement Ratio)

  8. What do we mean by “Functional Forms”?

  9. Non-Parametric Example

  10. Georges Bank Haddock - Catches

  11. Index Method Replacement ratio “6-panel” Plots

  12. 5.1/X = 0.23, applying algebra, Target Biomass Index = 22.17 MSY/ Biomass Index = relF

  13. Gulf of Maine and Georges Bank Haddock Closely Linked

  14. Fs – 2000 MSY, rebuild

  15. 2001 Catches vs. MSYs Sum 2001 = 69.2 Sum MSY = 192.9 (36%)

  16. “Jackknife Plots” Each Stock Plotted Vs. sum of all others Circles are each year

  17. Specific Results & Advice • Biomass and Fishing mortality reference points have been updated for 15 of the 19 stocks considered • For only two stocks the surplus production estimates of Bmsy and Fmsy are retained (GB Winter Flounder, White Hake) • For all stocks, reference point estimation is now compatible with stock monitoring methods • No indication that Multispecies interactions will limit attainment of revised biomass targets • Projections in the medium term are problematic for a few stocks • Working Group recommends an Adaptive Approach to Biomass • Management

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