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Accurate estimates of tag-induced mortality rates are contingent on the number of tagged and recaptured lobsters

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Kordjazi, Z, Frusher, S ORCID: 0000-0003-2493-3676, Buxton, CD, Gardner, C ORCID: 0000-0003-0324-4337 and Bird, T 2018 , 'Accurate estimates of tag-induced mortality rates are contingent on the number of tagged and recaptured lobsters' , Bulletin of Marine Science, vol. 94, no. 3 , pp. 1017-1034 , doi: 10.5343/bms.2017.1098.

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Abstract

Tag-induced mortality (TIM) biases manycapture-recapture studies, leading to abnormally highmortality estimates in the first-year post-tagging. Althoughmodels exist to account for this bias, estimating TIM hasbeen problematic and restricted to artificial environments.Here, we use a method for estimating Jasus edwardsii(Hutton, 1875) TIM in situ and demonstrate the conditionsunder which accurate estimates can be achieved. We usea long-term capture-mark-recapture study conductedsince 2000 at the Crayfish Point Scientific Reserve (CPSR),Hobart, Tasmania, Australia, to estimate the rate of in situtag induced mortality and demonstrate the assumptionsrelating to sampling design that are required to achieveaccurate estimates. TIM estimates were high and relativelysimilar for both males and females. The similarity betweensexes would indicate that for this species, combined sexestimates may be sufficient, which requires substantiallyless effort. Estimates of TIM were sensitive to the numberof recaptured lobsters and at least 15 lobsters, tagged in aninitial survey, had to be captured in two subsequent surveys.As recapture rates for lobsters over two subsequent recaptureevents are relatively low, this resulted in a large number oflobsters needing to be tagged in the initial survey. Given thatmost tagging studies have at least three surveys, we suggestthat the design incorporate the ability to also estimate TIM.This is particularly important if tagging studies are usedto estimate population parameters for exploited species,as not accounting for TIM would lead to overestimation ofresources and inappropriate catch allocations.

Item Type: Article
Authors/Creators:Kordjazi, Z and Frusher, S and Buxton, CD and Gardner, C and Bird, T
Keywords: Jasus edwardsii, tagging, mortality
Journal or Publication Title: Bulletin of Marine Science
Publisher: Rosenstiel Sch Mar Atmos Sci
ISSN: 0007-4977
DOI / ID Number: 10.5343/bms.2017.1098
Copyright Information:

© 2018 Rosenstiel School of Marine & Atmospheric Science of the University of Miami

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