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Longline CPUE standardization: IATTC 2006

Longline CPUE standardization: IATTC 2006. Simon Hoyle and Mark Maunder. Introduction. Longline fisheries Indices of abundance Statistical methods Results & discussion Model selection Diagnostics CPUE indices Compare with last year Parameter estimates. Longline fisheries. Northern.

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Longline CPUE standardization: IATTC 2006

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  1. Longline CPUE standardization: IATTC 2006 Simon Hoyle and Mark Maunder

  2. Introduction • Longline fisheries • Indices of abundance • Statistical methods • Results & discussion • Model selection • Diagnostics • CPUE indices • Compare with last year • Parameter estimates

  3. Longline fisheries Northern Southern

  4. Indices of abundance • Standardized CPUE assumed proportional to abundance • Japanese longline data, 1975 – 2004 • Provided by SPC • Catch in numbers, effort in hooks • Methods • 2005 – delta gamma GLM • 2003-2004 – neural networks • 1999-2002 – regression trees

  5. Statistical methods • Strata defined as 5º square / HBF category • Only strata with at least 5 non-zero catches are included • Delta lognormal model • w = g(Year.qtr, Lat.Long, HBF, effort) • f(y) = h(Year.qtr, Lat.Long, HBF)

  6. Change from last year • In 2005 • Used delta gamma model • Didn’t include effort in delta component of GLM • Delta lognormal fit the data better (AIC) • Change makes very little difference to results

  7. Catch and effort (northern)

  8. Catch and effort (southern)

  9. Un-standardized data – proportion zero & nonzero CPUE

  10. Model selection

  11. Residuals for non-zero component through time

  12. Residuals for non-zero component

  13. Standardized CPUE - bigeye

  14. Standardized CPUE - yellowfin

  15. Raw vs standardized CPUE

  16. Standardized CPUE / CPUE standardized by time only slope= -0.0051 ± 0.0006

  17. Standardized CPUE / CPUE standardized by time only slope = -0.007 ± 003

  18. Average HBF through time

  19. HBF parameters

  20. Bigeye south

  21. Yellowfin south

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