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Global catches, exploitation rates, and rebuilding options for sharks

Author

Listed:
  • Worm, Boris
  • Davis, Brendal
  • Kettemer, Lisa
  • Ward-Paige, Christine A.
  • Chapman, Demian
  • Heithaus, Michael R.
  • Kessel, Steven T.
  • Gruber, Samuel H.

Abstract

Adequate conservation and management of shark populations is becoming increasingly important on a global scale, especially because many species are exceptionally vulnerable to overfishing. Yet, reported catch statistics for sharks are incomplete, and mortality estimates have not been available for sharks as a group. Here, the global catch and mortality of sharks from reported and unreported landings, discards, and shark finning are being estimated at 1.44 million metric tons for the year 2000, and at only slightly less in 2010 (1.41 million tons). Based on an analysis of average shark weights, this translates into a total annual mortality estimate of about 100 million sharks in 2000, and about 97 million sharks in 2010, with a total range of possible values between 63 and 273 million sharks per year. Further, the exploitation rate for sharks as a group was calculated by dividing two independent mortality estimates by an estimate of total global biomass. As an alternative approach, exploitation rates for individual shark populations were compiled and averaged from stock assessments and other published sources. The resulting three independent estimates of the average exploitation rate ranged between 6.4% and 7.9% of sharks killed per year. This exceeds the average rebound rate for many shark populations, estimated from the life history information on 62 shark species (rebound rates averaged 4.9% per year), and explains the ongoing declines in most populations for which data exist. The consequences of these unsustainable catch and mortality rates for marine ecosystems could be substantial. Global total shark mortality, therefore, needs to be reduced drastically in order to rebuild depleted populations and restore marine ecosystems with functional top predators.

Suggested Citation

  • Worm, Boris & Davis, Brendal & Kettemer, Lisa & Ward-Paige, Christine A. & Chapman, Demian & Heithaus, Michael R. & Kessel, Steven T. & Gruber, Samuel H., 2013. "Global catches, exploitation rates, and rebuilding options for sharks," Marine Policy, Elsevier, vol. 40(C), pages 194-204.
  • Handle: RePEc:eee:marpol:v:40:y:2013:i:c:p:194-204
    DOI: 10.1016/j.marpol.2012.12.034
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    Citations

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    Cited by:

    1. Andrew T Fields & Debra L Abercrombie & Rowena Eng & Kevin Feldheim & Demian D Chapman, 2015. "A Novel Mini-DNA Barcoding Assay to Identify Processed Fins from Internationally Protected Shark Species," PLOS ONE, Public Library of Science, vol. 10(2), pages 1-10, February.
    2. Erhardt, Tobias & Weder, Rolf, 2015. "Shark Hunting: International Trade and the Imminent Extinction of Heterogeneous Species," Working papers 2015/07, Faculty of Business and Economics - University of Basel.
    3. Garla, Ricardo C. & Freitas, Renato H.A. & Calado, Janaina F. & Paterno, Gustavo B.C. & Carvalho, Adriana R., 2015. "Public awareness of the economic potential and threats to sharks of a tropical oceanic archipelago in the western South Atlantic," Marine Policy, Elsevier, vol. 60(C), pages 128-133.
    4. Jordan S Goetze & Tim J Langlois & Joe McCarter & Colin A Simpfendorfer & Alec Hughes & Jacob Tingo Leve & Stacy D Jupiter, 2018. "Drivers of reef shark abundance and biomass in the Solomon Islands," PLOS ONE, Public Library of Science, vol. 13(7), pages 1-16, July.
    5. Humber, Frances & Andriamahefazafy, Mialy & Godley, Brendan John & Broderick, Annette Cameron, 2015. "Endangered, essential and exploited: How extant laws are not enough to protect marine megafauna in Madagascar," Marine Policy, Elsevier, vol. 60(C), pages 70-83.
    6. André S Afonso & Fábio H V Hazin, 2015. "Vertical Movement Patterns and Ontogenetic Niche Expansion in the Tiger Shark, Galeocerdo cuvier," PLOS ONE, Public Library of Science, vol. 10(1), pages 1-26, January.
    7. Sybersma, Stacie, 2015. "Review of shark legislation in Canada as a conservation tool," Marine Policy, Elsevier, vol. 61(C), pages 121-126.
    8. Erhardt, Tobias & Weder, Rolf, 2020. "Shark hunting: On the vulnerability of resources with heterogeneous species," Resource and Energy Economics, Elsevier, vol. 61(C).
    9. Po-Shun Chuang & Tzu-Chiao Hung & Hung-An Chang & Chien-Kang Huang & Jen-Chieh Shiao, 2016. "The Species and Origin of Shark Fins in Taiwan’s Fishing Ports, Markets, and Customs Detention: A DNA Barcoding Analysis," PLOS ONE, Public Library of Science, vol. 11(1), pages 1-13, January.
    10. Friedrich, Laura A. & Jefferson, Rebecca & Glegg, Gillian, 2014. "Public perceptions of sharks: Gathering support for shark conservation," Marine Policy, Elsevier, vol. 47(C), pages 1-7.
    11. Diego Cardeñosa & Andrew Fields & Debra Abercrombie & Kevin Feldheim & Stanley K H Shea & Demian D Chapman, 2017. "A multiplex PCR mini-barcode assay to identify processed shark products in the global trade," PLOS ONE, Public Library of Science, vol. 12(10), pages 1-9, October.
    12. Mariana G Bender & Gustavo R Machado & Paulo José de Azevedo Silva & Sergio R Floeter & Cassiano Monteiro-Netto & Osmar J Luiz & Carlos E L Ferreira, 2014. "Local Ecological Knowledge and Scientific Data Reveal Overexploitation by Multigear Artisanal Fisheries in the Southwestern Atlantic," PLOS ONE, Public Library of Science, vol. 9(10), pages 1-9, October.
    13. Oliver, Shelby & Braccini, Matias & Newman, Stephen J. & Harvey, Euan S., 2015. "Global patterns in the bycatch of sharks and rays," Marine Policy, Elsevier, vol. 54(C), pages 86-97.

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