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ASSESSMENT OF BIGEYE TUNA ( THUNNUS OBESUS ) IN THE EASTERN PACIFIC OCEAN

ASSESSMENT OF BIGEYE TUNA ( THUNNUS OBESUS ) IN THE EASTERN PACIFIC OCEAN. January 1975 – December 2005. Overview of assessment. Age-structured, statistical, catch-at-length model (A-SCALA). Quarterly time step from 1975 to the start of 2005.

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ASSESSMENT OF BIGEYE TUNA ( THUNNUS OBESUS ) IN THE EASTERN PACIFIC OCEAN

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  1. ASSESSMENT OF BIGEYE TUNA (THUNNUS OBESUS) IN THE EASTERN PACIFIC OCEAN January 1975 – December 2005

  2. Overview of assessment • Age-structured, statistical, catch-at-length model (A-SCALA). • Quarterly time step from 1975 to the start of 2005. • No net movement of fish between the eastern and western Pacific.

  3. Major changes • No major model changes except new and updated catch, effort, and length-frequency data.

  4. Sensitivity analyses • Spawner-recruitment relationship (steepness = 0.75) • Assumed value for the asymptotic length parameter of the Richards growth curve • Inclusion of the Chinese Taipei longline length-frequcy data • Relationship between recruitment an the el Nino index

  5. 8 5, 13 9 3, 11 4, 12 1, 6-7 2, 10 Bigeye fishery definitions Recent FLT (2-5) Discards (10-13) N Longline (8) S Longline (9) Early FLT (1) Early & Recent UNA (6, 7)

  6. S LL N Offshore FLT Early UNA Recent UNA N LL Early FLT S Offshore FLT Equatorial FLT Coastal FLT Catch

  7. Effort S LL Recent UNA N LL N Offshore FLT Early UNA Equatorial FLT Coastal FLT Early FLT S Offshore FLT

  8. S LL N Offshore FLT Early UNA Recent UNA N LL Early FLT S Offshore FLT Equatorial FLT Coastal FLT CPUE

  9. Recent UNA N LL S LL Coastal FLT N Offshore FLT Early UNA Early FLT S Offshore FLT Equatorial FLT Length frequency data

  10. Discards Northern FLT Inshore FLT Southern FLT Equatorial FLT

  11. Results • Fit to the length frequency • Growth • Fishing mortality • Selectivity • Recruitment • Biomass • Catchability

  12. Recent UNA N LL S LL Coastal FLT N Offshore FLT Early UNA Early FLT S Offshore FLT Equatorial FLT Average fit to the length frequency data

  13. Fit to recent length frequency data

  14. Fit to recent length frequency data

  15. Growth

  16. Fishing mortality 1-4 5-8 13-16 9-12 21-24 17-20 29-32 25-28 37-40 33-36

  17. Age-specific fishing mortality

  18. Selectivity Recent UNA N LL Early UNA S LL Coastal FLT N Offshore FLT Early FLT S Offshore FLT Equatorial FLT

  19. Catchability N Offshore FLT Equatorial FLT Coastal FLT Early FLT S Offshore FLT

  20. S LL N LL Recent UNA Early UNA Catchability

  21. Northern FLT Inshore FLT Equatorial FLT Southern FLT Catchability

  22. Recruitment

  23. Biomass

  24. Spawning biomass

  25. No-fishing plot

  26. Average weight Combined Surface Combined LL Early UNA Recent UNA N LL S LL Early FLT Coastal FLT N Offshore FLT Galapagos FLT S Offshore FLT

  27. Biomass

  28. Recruitment

  29. Comparisons to reference points • Spawning biomass depletion • Yield curve

  30. Spawning biomass ratio

  31. SBR comparison with last year

  32. Time varying indicators

  33. Yield curve

  34. AMSY-quantities

  35. AMSY-quantities -- assumed F

  36. AMSY-quantities – by fishery

  37. Forward simulations • Spawning biomass depletion • Biomass • Surface fishery catch • Longline catch

  38. Spawning biomass ratio

  39. Biomass

  40. Predicted catches

  41. Stock-recruitment relationship (h = 0.75)

  42. Biomass

  43. Recruitment

  44. Spawning biomass ratio

  45. Spawner-recruitment curve

  46. Yield curve

  47. Assumed value for the asymptotic length parameter of the Richards growth curve

  48. Growth curves

  49. Maximum length

  50. Likelihoods

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