1. Yellowfin Tuna 1975-2005

2. Major Changes Catch, effort, and length-frequency data for the surface fisheries have been updated to include new data for 2005 and revised data for 1975-2004. Catch data for the Japanese longline fisheries have been updated for 2000-2003 and to include new data for 2004. Catch data for the longline fisheries of Chinese Taipei have been updated for 2002 and new data added for 2003. Catch data fore the longline fisheries of Korea have been updated to include new data for 2003 Catch data for the longline fisheries of the Peoples Republic of China have been updated to include new data for 2003 and 2004. Longline catch-at-length data for 2002-2003 have been updated and new data for 2004 added. Longline catch per unit effort data have been standardized using a delta-lognormal model, updated to include 2004 data. Growth model has been changed to fix length-at-age at the prior distribution of a Richards growth curve based on otolith data

3. Sensitivity Analyses Stock recruitment relationship Asymptotic length

4. Data Fishery definitions Catch Effort Length frequency

5. Yellowfin Fishery Definitions

6. Catch FO southFO centralFO coastal FO north DOL south DOL coastal DOL north NA south NA north LL south LL north BB DIS southDIS northDIS coastalDIS central

7. Effort FO south FO central FO coastal FO north DOL south DOL coastal DOL north NA south NA north LL south LL north BB DIS south DIS north DIS coastal DIS central

8. CPUE FO south FO central FO coastal FO north DOL south DOL coastal DOL north NA south NA north LL south LL north BB DIS south DIS north DIS coastal DIS central

9. Fixed Parameters Natural Mortality Fecundity at age Sex ratio at age Selectivity curves for the discard fisheries The steepness of the stock recruitment relationship = 1 (no relationship)

10. Natural Mortality Age in quarters -- Edad en trimestres Quarterly M -- M Trimestral 0.0 0.1 0.2 0.3 0.4 0.5 481216202428

11. Sex Ratio Age in quarters Percent female 0510152025 0.0 0.1 0.2 0.3 0.4 0.5

12. Relative Fecundity Age in quarters Relative fecundity x maturity 0510152025 0 1 2 3 4 5 6

13. Estimated parameters Recruitment Temporal anomalies, (no Seasonal component) Catchability Temporal anomalies Selectivity Initial population size and age-structure Mean length at age Variation of length at age

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

15. Fit to the length-frequency FO south FO centralFO coastalFO north DOL south DOL coastal DOL northNA south NA north LL south LL north BB

16. Growth

17. Fishing mortality

18. Age Specific Fishing Mortality

19. Selectivity FO south FO central FO coastal FO north DOL south DOL coastal DOL north NA south NA north LL south LL north BB DIS southDIS northDIS coastal DIS central

20. Catchability FO south FO central FO coastal FO north DOL south DOL coastal DOL north NA south NA north LL south LL north BB

21. Recruitment

22. Recent length-frequency data (FO) FO southFO centralFO coastalFO north 23 41

23. Recent length-frequency data (Unassociated) NA south NA north

24. Recent length-frequency data (Dolphin associated) DOL south DOL coastal DOL north

25. Recent length-frequency data (longline) LL southLL north

26. Stock - recruitment

27. Biomass

28. Spawning Biomass

29. Average weight FO southFO centralFO coastalFO north DOL south DOL coastalDOL northNA south NA north LL south LL north BB Surface Longline

30. No Fishing

31. Fishery impact

32. No Fishing and Fishery Impact

33. Biomass Comparisons

34. Reference points & projections Assumptions –For MSY calculations Average of 2002-2003 for fishing mortality –For forward projections Average of 2002-2003 for catchability 2004 effort

35. SBR

37. AMSY by method FisheryAMSYB AMSY S AMSY B AMSY /B F=0 S AMSY /S F=0 F multiplier PesqueríaRMSPB RMSP S RMSP B RMSP /B F=0 S RMSP /S F=0 Multiplica dor de F All— Todos 287 519416 3794 6770.360.371.02 OBJ 214 243316 3313 5200.270.2811.06 NOA 259 574385 2284 3920.330.344.20 DEL 304 745406 3694 3350.350.342.11 LL 350 562460 6734 9610.39 25.18

38. AMSY with method removed FisheryAMSYB AMSY S AMSY B AMSY /B F=0 S AMSY /S F=0 F multiplier PesqueríaRMSPB RMSP S RMSP B RMSP /B F=0 S RMSP /S F=0 Multiplica dor de F All— Todos 287 519416 3794 6770.360.371.02 No FLT 295 231416 0624 6070.36 1.20 No UNA 296 439421 7194 6870.360.371.39 No DOL 268 587419 1204 8940.360.382.08 No LL 282 176406 7554 5490.350.361.12

39. AMSY with effort adjusted All gears Purse- seine only Longline only Purse- seine scaled Longline scaled Base AMSY—RMSP287 519282 176373 759287 625306 171 B AMSY —B RMSP 416 379406 755577 040433 243327 698 S AMSY —S RMSP 4 6774 5496 7554 9203 204 B AMSY /B 0 —B RMSP /B 0 0.360.350.410.370.28 S AMSY /S 0 —S RMSP /S 0 0.370.360.440.390.25 F multiplier—Multiplicador de F1.021.1212.410.9419.62

40. Yield

41. AMSY quantities using F(y)

42. Sensitivity: h = 0.75 When the spawning population is 20% of its unexploited level the recruitment is 75% of its unexploited level Biomass Recruitment SBR Yield Curve AMSY

43. Biomass Comparison

44. Recruitment

46. SBR

47. Yield Curve

48. Sensitivity to L ∞ : proportion YFT > given length

49. Maximum length observed by yr

50. Sensitivity to assumed L ∞ : Biomass

51. Recruitment

52. Spawning biomass ratio

53. Selectivity Base case L ∞ = 200 L ∞ = 170

54. AMSY table

55. Forward Simulations Depletion ratio Surface fishery catch Longline catch

56. SBR

57. Catch

58. Catch with median catchability

59. Summary: Main Results The results are similar to the previous four assessments, except that SBR at SBR AMSY is lower than in the last assessment The biomass is estimated to have declined slightly in 2005 There is uncertainty about recent and future recruitment and biomass levels

60. What is robust The trend in biomass The regime shift in recruitment

61. Plausible Sensitivities and Uncertainties The stock recruitment relationship Asymptotic length Uncertainty in current biomass and recruitment

62. Conclusions 1.The biomass is estimated to have declined slightly in 2005 2.The current SBR may be close to the SBR required to produce AMSY 3.The current fishing mortality rates are close to those required to produce AMSY 4.The average weight of a yellowfin in the catch is much less than the critical weight and increasing the average weight could increase AMSY 5.There have been two different productivity regimes and the levels of AMSY and the biomass required to produce AMSY may differ between the regimes

63. The END