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Estimating the number of whales entering trade using DNA profiling and capture-recapture analysis of market products

Authors

  • C. SCOTT BAKER,

    1. Marine Mammal Institute, Hatfield Marine Science Center, 2030 SE Marine Science Drive, Oregon State University, Newport, OR 97365, USA,
    2. School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand,
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  • JUSTIN G. COOKE,

    1. Centre for Ecosystem Management Studies, Alexander St. 10, 79261 Gutach, Germany,
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  • SHANE LAVERY,

    1. School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand,
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  • MEREL L. DALEBOUT,

    1. School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand,
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    • ††

      Present address: School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia

  • YONG-UN MA,

    1. Korean Federation for Environmental Movement, 251 Nuha-dong, Jongno-gu, Seoul, 110-806, Republic of Korea,
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  • NAOKO FUNAHASHI,

    1. Japan representative, International Fund for Animal Welfare, 1-2-10 Koyama, HigashiKurume-shi, Tokyo 203-0051, Japan,
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  • COLM CARRAHER,

    1. School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand,
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  • ROBERT L. BROWNELL JR

    1. NMFS Southwest Fisheries Science Centre, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA
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  • Note: The first author was responsible for directing market surveys and primary genetic analysis of market products. The second author was responsible for development of the statistical model for capture-recapture analysis.

C. Scott Baker, Fax: +1 541 867 0345; E-mail: scott.baker@oregonstate.edu

Abstract

Surveys of commercial markets combined with molecular taxonomy (i.e. molecular monitoring) provide a means to detect products from illegal, unregulated and/or unreported (IUU) exploitation, including the sale of fisheries bycatch and wild meat (bushmeat). Capture-recapture analyses of market products using DNA profiling have the potential to estimate the total number of individuals entering the market. However, these analyses are not directly analogous to those of living individuals because a ‘market individual’ does not die suddenly but, instead, remains available for a time in decreasing quantities, rather like the exponential decay of a radioactive isotope. Here we use mitochondrial DNA (mtDNA) sequences and microsatellite genotypes to individually identify products from North Pacific minke whales (Balaenoptera acutorostrata ssp.) purchased in 12 surveys of markets in the Republic of (South) Korea from 1999 to 2003. By applying a novel capture-recapture model with a decay rate parameter to the 205 unique DNA profiles found among 289 products, we estimated that the total number of whales entering trade across the five-year survey period was 827 (SE, 164; CV, 0.20) and that the average ‘half-life’ of products from an individual whale on the market was 1.82 months (SE, 0.24; CV, 0.13). Our estimate of whales in trade (reflecting the true numbers killed) was significantly greater than the officially reported bycatch of 458 whales for this period. This unregulated exploitation has serious implications for the survival of this genetically distinct coastal population. Although our capture-recapture model was developed for specific application to the Korean whale-meat markets, the exponential decay function could be modified to improve the estimates of trade in other wildmeat or fisheries markets or abundance of living populations by noninvasive genotyping.

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