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Method

ESTIMATING INDICES OF RELATIVE ABUNDANCE FOR YELLOWFIN TUNA FROM CATCH-PER-UNIT-OF-EFFORT ON SCHOOLS ASSOCIATED WITH DOLPHINS Mark N. Maunder and Simon D. Hoyle.

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Method

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  1. ESTIMATING INDICES OF RELATIVE ABUNDANCE FOR YELLOWFIN TUNA FROM CATCH-PER-UNIT-OF-EFFORT ON SCHOOLS ASSOCIATED WITH DOLPHINSMark N. Maunder and Simon D. Hoyle

  2. Goal: Develop an index of relative abundance from purse seine catch and effort data on schools associated with dolphinsProblem: In addition to making sets on schools associated with dolphins, vessels can also set on schools associated with floating objects and unassociated schools Concept: Only use vessels that make the majority of their sets on schools associated with dolphins

  3. Method • Restrict data to vessels that made • 80% or more of their sets on dolphin-associated tunas • 90% or more of their sets on either dolphin-associated or unassociated schools. • Apply a two GLMs with covariates • Time in quarters, month, and latitude • Time in quarters, vessel, aircraft, and sonar.

  4. Results

  5. Discussion • Restrict data to vessels that made sets on dolphin-associated tunas or standardization for the covariates did not have a large impact on the index of relative abundance • The results are consistent with the stock assessment estimates of abundance • Search time should be used as the measure of effort by eliminating the time taken to conduct a set (Punsly, 1987) .

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