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SSC Report to CFMC

SSC Report to CFMC. 146 th CFMC Meeting held June 24, 2013 SSC Meeting held June 19 – 20, 2013. SEDAR 30: Assessed blue tang and queen triggerfish TIP data from 1981 - 2011. Juvenile blue tang Acanthurus coeruleus. Queen triggerfish Balistes vetula. Barbara Kojis.

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SSC Report to CFMC

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  1. SSC Report to CFMC 146th CFMC Meeting held June 24, 2013 SSC Meeting held June 19 – 20, 2013

  2. SEDAR 30: Assessed blue tang and queen triggerfish TIP data from 1981 - 2011 Juvenile blue tang Acanthuruscoeruleus Queen triggerfish Balistesvetula Barbara Kojis L. Johnson, Fishbase

  3. School of primarily blue tang at Buck Island St. Croix, USVI

  4. Goal of SEDAR 30 • Determine stock status for blue tang and queen triggerfish • Given data limitations abundance could not be determined • Conducted mean length analyses to evaluate stock status in terms of mortality

  5. Data sources reviewed during SEDAR 30 • Marine Recreational Fisheries Statistics Survey (MRFSS) • Puerto Rico only • Commercial landings • By island platform and gear • Trip Interview Program (TIP) • Life history information • Published literature

  6. MRFSS in Puerto Rico • Blue tang • Five intercepted trips that retained or indicated discarding blue tang • Two length measurements • Queen triggerfish • Less than 20 intercepted trips per year retained or discarded queen triggerfish • Sixty length measurements • Was not used for assessment

  7. Commercial landings • USVI • 1974-1995 - catch reported as snapper/grouper or finfish • 1997 – reported to species group • Surgeonfishes • Triggerifshes • Puerto Rico • Species specific • Known problems with under-reporting • Commercial landings were not used for assessment

  8. Trip Interview Program – Blue tang

  9. Trip Interview Program – Queen triggerfish

  10. Mean length analysis • Length-frequency data were adequate for the pot and trap fisheries for both species • Except in Puerto Rico for blue tang • Used the Gedamke-Hoenig mean length estimator to obtain estimates of total mortality and evaluate how mortality has changed over time

  11. Mean length analysis • Model inputs • von Bertalanffy growth coefficient, k • From published literature • Asymptotic length, • From published literature • Species-specific length • Length-at-full vulnerability, • Mean length of fish larger than , • From TIP database

  12. Mean length analysis • Beverton-Holt mean length mortality estimator growth rate maximum length length at which all animals are fully vulnerable to gear total mortality mean length

  13. TIP length-frequency data – blue tang N = 860 N = 66 N = 499 N =223 N = 498 N = 840

  14. TIP length-frequency data – blue tang N = 13201 N = 2104 N = 629 N =11771 N = 3340 N = 1175

  15. TIP length-frequency data – queen triggerfish N = 2631 N = 536 N =1062 N =328 N = 323 N = 37

  16. TIP length-frequency data – queen triggerfish N = 2224 N = 276 N =495 N =638 N = 876 N = 3221

  17. TIP length-frequency data – queen triggerfish N = 3919 N = 757 N = 2168 N =94 N = 888 N = 199

  18. Blue tang life history information

  19. Blue tang growth curves

  20. Queen triggerfish life history information

  21. Queen triggerfish growth curves

  22. Mean length analysis • Model is run first assuming no change in mortality and then with increased complexity • Sensitivity analysis was conducted to characterize uncertainty in the mortality estimates

  23. Blue tang, St. Thomas Lc= 19cm, L∞ = 23.1cm, K= 0.49 Z1983 = 0.09 Z1984-2010 = 0.4

  24. Comparison of fishing mortality and natural mortality • Blue tang, St. Thomas/St. John Frequency Cumulative percent F/M

  25. Comparison of fishing mortality and natural mortality • Blue tang, St. Croix Frequency Cumulative percent F/M

  26. Queen triggerfish , Puerto Rico Lc = 29cm, L∞= 41.5cm, and K = 0.3y-1

  27. Comparison of fishing mortality and natural mortality • Queen triggerfish, Puerto Rico Frequency Cumulative percent F/M

  28. Queen triggerfish , St. Thomas/St. John Lc = 34cm, L∞ = 41.5cm, and K = 0.3y-1

  29. Comparison of fishing mortality and natural mortality • Queen triggerfish, St. Thomas/St. John Frequency Cumulative percent F/M

  30. Queen triggerfish , St. Croix Lc = 28cm, L∞ = 41.5cm, and K = 0.3y-1 Z = 1.07 Z = 0.7

  31. Comparison of fishing mortality and natural mortality • Queen triggerfish, St. Croix Frequency Cumulative percent F/M

  32. Main conclusions from AW report for blue tang: Puerto Rico The AW panel decided that data was insufficient to conduct length-based analysis. St. Thomas / St. John Results from length-based analysis suggests that total mortality increased, Year of change and magnitude of change was variable among the sensitivity runs. Uncertainty about whether fishing mortality is higher than natural mortality (i.e., proxy for FMSY). Annual length-frequency data have been relatively stable over the time series. St. Croix Results from length-based analysis suggests that total mortality increased in 1983 (first year of available data), Magnitude of change was variable and dependent on parameter inputs. Uncertainty about whether fishing mortality is higher than natural mortality (i.e., proxy for FMSY). Annual length-frequency data have been stable between 1984-2012.

  33. Main conclusions from AW report for blue tang: General conclusions Available age-growth relationships suggest two possible explanations of growth (k = 0.4 or k = 0.8-1) adding to the uncertainty surrounding the mortality estimates Well-designed growth studies are needed for this species Age-growth relationship erodes at an early age relative to the blue tang life span Length analysis may be inappropriate for this species Collection of catch-at-age data may be more appropriate to adequately describe changes in blue tang population structure.

  34. Main conclusions from AW report for queen triggerfish: Puerto Rico Results from length analysis suggest that total mortality declined in 1998 or 1999, An increase in mean length can be due to reduction in mortality or expansion to relatively unfished areas. Without detailed spatial catch data, it is difficult to separate these effects Uncertainty about whether fishing mortality is higher than natural mortality (i.e., proxy for FMSY). USVI Results from length analysis suggest that mortality has remained unchanged in St. Thomas/ St. John over time and increased in St. Croix in 1985 or 1986. Industry representatives indicated that they release queen triggerfish >45cm. Violates model assumption of knife-edge selectivity Makes it difficult to interpret absolute mortality estimates General conclusions Available life history information suggested two different life strategies for queen triggerfish Age and growth studies are needed

  35. SSC’s Review of SEDAR 30 • The SSC accepted the results for queen triggerfish and blue tang as the best available at this time recognizing the following limitations: • Lack of life history information • Low information content provided by the length frequency data for blue tang because of its determinant growth • Potential violation of model assumptions because of dome shaped selectivity for queen triggerfish in STT/STJ due to discards of large fish • Uncertainty in the data due to inconsistencies in annual sample size and non-randomness of samples • Inability to address biomass benchmarks due to considerable uncertainty in landings data

  36. Conclusions - Queen triggerfish • The SSC concluded that the results of SEDAR 30 are consistent with the current status determination in PR and STT/STJ, which is that queen triggerfish is not undergoing overfishing. • However, the result for STX indicates that overfishing might be occurring.

  37. Conclusions - Blue Tang • Results were too uncertain to be used for status determination • Blue tang does not appear to be targeted in PR based on lack of reported landings • Given the above, the SSC finds no basis for changing the ABCs for queen triggerfish and blue tang.

  38. Recommendatons • For blue tang length analysis is not appropriate and the SSC recommends collecting catch at age data to inform an age-structure model. • For the queen triggerfish in St. Croix, the SSC recommends that approximately 500 length measurements be taken within the next year to inform further analysis. •  There is an urgent need for local age and life history parameters for the two species. Without the basic life history and age information, the assessments will continue not to be very informative for scientific advice and management. The SSC understands that a new collection of otoliths is under way and recommends that a carefully designed sampling protocol be implemented. • Validation of catch data including expansion factors is also urgently needed.

  39. Derivation of fishing mortality-based references points and the determination of overfishing status of queen snapper and silk snapper captured in the US Caribbean June 19, 2013 SEFSC Miami, Florida

  40. Review of SEDAR 26 • Assessed species • Queen snapper, Etelisoculatus • Silk snapper, Lutjanus vivanus • Island platforms and gear types were assessed separately • Queen snapper • Puerto Rico, hook and line • St. Croix, hook and line • Silk snapper • St. Croix, hook and line T. Meyer, FishBase.org D. Bryan, FishBase.org

  41. Review of SEDAR 26 • Data • Trip Interview Program (TIP) • Annual length data • Most consistent species-specific data among the platforms

  42. Review of SEDAR 26 • Gedamke-Hoenig mean length estimator • Computationally attractive for data limited situations – Minimal data inputs • Length-frequency data – Mean length and length-at-full recruitment • Life-history parameters – von Bertalanffy growth parameters • Provides estimates of total mortality • Fishing mortality can be derived from total mortality and estimates of natural mortality • Does not assume population is at equilibrium • Estimates temporal changes in total mortality

  43. Review of SEDAR 26 • Uncertainty in assessment • Life history parameters were highly uncertain • Sensitivity analysis was conducted • Conducted assessment over a range of the input parameters

  44. SEDAR 26 Assessment Conclusions • Queen snapper, hook and line fishery in St. Croix • No evidence to suggest overfishing

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