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

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posted on 2023-05-19, 02:16 authored by Smart, JJ, Chin, A, Baje, L, Madeline GreenMadeline Green, Appleyard, SA, Tobin, AJ, Simpfendorfer, CA, White, WT
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- = 159 cm TL and L-0 = 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.

History

Publication title

PLoS ONE

Volume

11

Issue

4

Article number

e0153116

Number

e0153116

Pagination

1-18

ISSN

1932-6203

Department/School

Institute for Marine and Antarctic Studies

Publisher

Public Library of Science

Place of publication

United States

Rights statement

Copyright 2016 Smart et al. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) https://creativecommons.org/licenses/by/4.0/

Repository Status

  • Open

Socio-economic Objectives

Wild caught fin fish (excl. tuna)

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