Effects of including misidentified sharks in life history analyses: a case study on the grey reef shark Carcharhinus amblyrhynchos from Papua New Guinea

Smart, Jonathan J., Chin, Andrew, Baje, Leontine, Green, Madeline E., Appleyard, Sharon A., Tobin, Andrew J., Simpfendorfer, Colin A., and White, William T. (2016) Effects of including misidentified sharks in life history analyses: a case study on the grey reef shark Carcharhinus amblyrhynchos from Papua New Guinea. PLoS ONE, 11 (4). e0153116. pp. 1-18.

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Abstract

Fisheries observer programs are used around the world to collect crucial information and samples that inform fisheries management. However, observer error may misidentify similar -looking shark species. This raises questions about the level of error that species misidentifications could introduce to estimates of species' life history parameters. This study addressed these questions using the Grey Reef Shark Carcharhinus amblyrhynchos as a case study. Observer misidentification rates were quantified by validating species identifications using diagnostic photographs taken on board supplemented with DNA barcoding. Length-at-age and maturity ogive analyses were then estimated and compared with and without the misidentified individuals. Vertebrae were retained from a total of 155 sharks identified by observers as C. amblyrhynchos. However, 22 (14%) of these were sharks were misidentified by the observers and were subsequently re -identified based on photographs and/or DNA barcoding. Of the 22 individuals misidentified as C. amblyrhynchos, 16 (73%) were detected using photographs and a further 6 via genetic validation. If misidentified individuals had been included, substantial error would have been introduced to both the length -at -age and the maturity estimates. Thus validating the species identification, increased the accuracy of estimated life history parameters for C. amblyrhynchos. From the corrected sample a multi -model inference approach was used to estimate growth for C. amblyrhynchos using three candidate models. The model averaged length-at-age parameters for C. amblyrhynchos with the sexes combined were (L) over bar infinity= 159 cm TL and L,= 72 cm TL. Females mature at a greater length (l₅₀ = 136 cm TL) and older age (A₅₀) = 9.1 years) than males (l₅₀ = 123 cm TL; A₅₀ = 5.9 years). The inclusion of techniques to reduce misidentification in observer programs will improve the results of life history studies and ultimately improve management through the use of more accurate data for assessments.

Item ID: 44014
Item Type: Article (Research - C1)
ISSN: 1932-6203
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© 2016 Smart et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. https://creativecommons.org/licenses/by/4.0/

This publication was included as Chapter 5 of the following PhD thesis: Smart, Jonathan James (2016) Life history and demographic modelling of shark species caught in Indo-Pacific fisheries. PhD thesis, James Cook University, which is available Open Access in ResearchOnline@JCU. Please see the Related URLs for access.

Funders: Australian Centre for International Agricultural Research (ACIAR), National Fisheries Authority (NFA), Commonwealth Scientific and Industrial Research Organisation (CSIRO), James Cook University (JCU), Australian Postgraduate Award (APA), Oceania Chondrichthyan Society (OCS)
Projects and Grants: ACIAR project FIS/2012/102, OCS Passions of Paradise Award, CSIRO Wealth from Oceans Scholarship
Date Deposited: 04 May 2016 07:39
FoR Codes: 07 AGRICULTURAL AND VETERINARY SCIENCES > 0704 Fisheries Sciences > 070402 Aquatic Ecosystem Studies and Stock Assessment @ 70%
06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 30%
SEO Codes: 83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8302 Fisheries - Wild Caught > 830204 Wild Caught Fin Fish (excl. Tuna) @ 70%
96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960507 Ecosystem Assessment and Management of Marine Environments @ 30%
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