Accuracy of species identification by fisheries observers in a north Australian shark fishery

Bree Tillett, Iain Field, Corey Bradshaw, Grant Johnson, Rik BUCKWORTH, Mark G Meekan, Jennifer Ovenden

    Research output: Contribution to journalArticleResearchpeer-review

    Abstract

    Despite the importance of observers to collect data for effective fisheries management worldwide, their species-identification abilities are rarely assessed. Misidentifications could compromise observer data particularly in diverse, multi-species fisheries such as those in the tropics where visual identification is challenging. Here, we provide the first estimates of the ability of scientific observers to identify five species of morphologically similar carcharhinid sharks (Carcharhinus leucas, C. amboinensis, C. tilstoni, C. sorrah and C. brevipinna) in a fishery in northern Australia. We compared observer field identifications of sharks with genetic validation (814. bp mtDNA NADH dehydrogenase subunit 4) to quantify species identification errors. We used binomial generalised linear models to determine the influences of species, gender, total length, and the observer's experience on identification error. We found that identification error (?20%) depended predominately on the species in question (highest error for C. tilstoni). Male sharks were misidentified less frequently than females, and error decreased marginally with increasing total length. Surprisingly, we found no statistical evidence that observer experience influenced identification error. Our results provide the first benchmark of identification accuracy of observers for carcharhinid sharks in northern Australia and show that estimates of error in species identifications need to be incorporated into management strategies to ensure successful recovery of the many recently over-fished shark populations.
    Original languageEnglish
    Pages (from-to)109-115
    Number of pages7
    JournalFisheries Research
    Volume127-128
    DOIs
    Publication statusPublished - Sep 2012

    Fingerprint

    shark fishery
    sharks
    shark
    fishery
    fisheries
    Leucas
    Carcharhinus
    multispecies fishery
    NADH dehydrogenase
    fisheries management
    tropics
    fishery management
    mitochondrial DNA
    linear models
    species identification
    gender

    Cite this

    Tillett, B., Field, I., Bradshaw, C., Johnson, G., BUCKWORTH, R., Meekan, M. G., & Ovenden, J. (2012). Accuracy of species identification by fisheries observers in a north Australian shark fishery. Fisheries Research, 127-128, 109-115. https://doi.org/10.1016/j.fishres.2012.04.007
    Tillett, Bree ; Field, Iain ; Bradshaw, Corey ; Johnson, Grant ; BUCKWORTH, Rik ; Meekan, Mark G ; Ovenden, Jennifer. / Accuracy of species identification by fisheries observers in a north Australian shark fishery. In: Fisheries Research. 2012 ; Vol. 127-128. pp. 109-115.
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    title = "Accuracy of species identification by fisheries observers in a north Australian shark fishery",
    abstract = "Despite the importance of observers to collect data for effective fisheries management worldwide, their species-identification abilities are rarely assessed. Misidentifications could compromise observer data particularly in diverse, multi-species fisheries such as those in the tropics where visual identification is challenging. Here, we provide the first estimates of the ability of scientific observers to identify five species of morphologically similar carcharhinid sharks (Carcharhinus leucas, C. amboinensis, C. tilstoni, C. sorrah and C. brevipinna) in a fishery in northern Australia. We compared observer field identifications of sharks with genetic validation (814. bp mtDNA NADH dehydrogenase subunit 4) to quantify species identification errors. We used binomial generalised linear models to determine the influences of species, gender, total length, and the observer's experience on identification error. We found that identification error (?20{\%}) depended predominately on the species in question (highest error for C. tilstoni). Male sharks were misidentified less frequently than females, and error decreased marginally with increasing total length. Surprisingly, we found no statistical evidence that observer experience influenced identification error. Our results provide the first benchmark of identification accuracy of observers for carcharhinid sharks in northern Australia and show that estimates of error in species identifications need to be incorporated into management strategies to ensure successful recovery of the many recently over-fished shark populations.",
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    author = "Bree Tillett and Iain Field and Corey Bradshaw and Grant Johnson and Rik BUCKWORTH and Meekan, {Mark G} and Jennifer Ovenden",
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    language = "English",
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    Tillett, B, Field, I, Bradshaw, C, Johnson, G, BUCKWORTH, R, Meekan, MG & Ovenden, J 2012, 'Accuracy of species identification by fisheries observers in a north Australian shark fishery', Fisheries Research, vol. 127-128, pp. 109-115. https://doi.org/10.1016/j.fishres.2012.04.007

    Accuracy of species identification by fisheries observers in a north Australian shark fishery. / Tillett, Bree; Field, Iain; Bradshaw, Corey; Johnson, Grant; BUCKWORTH, Rik; Meekan, Mark G; Ovenden, Jennifer.

    In: Fisheries Research, Vol. 127-128, 09.2012, p. 109-115.

    Research output: Contribution to journalArticleResearchpeer-review

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    AU - Tillett, Bree

    AU - Field, Iain

    AU - Bradshaw, Corey

    AU - Johnson, Grant

    AU - BUCKWORTH, Rik

    AU - Meekan, Mark G

    AU - Ovenden, Jennifer

    PY - 2012/9

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    N2 - Despite the importance of observers to collect data for effective fisheries management worldwide, their species-identification abilities are rarely assessed. Misidentifications could compromise observer data particularly in diverse, multi-species fisheries such as those in the tropics where visual identification is challenging. Here, we provide the first estimates of the ability of scientific observers to identify five species of morphologically similar carcharhinid sharks (Carcharhinus leucas, C. amboinensis, C. tilstoni, C. sorrah and C. brevipinna) in a fishery in northern Australia. We compared observer field identifications of sharks with genetic validation (814. bp mtDNA NADH dehydrogenase subunit 4) to quantify species identification errors. We used binomial generalised linear models to determine the influences of species, gender, total length, and the observer's experience on identification error. We found that identification error (?20%) depended predominately on the species in question (highest error for C. tilstoni). Male sharks were misidentified less frequently than females, and error decreased marginally with increasing total length. Surprisingly, we found no statistical evidence that observer experience influenced identification error. Our results provide the first benchmark of identification accuracy of observers for carcharhinid sharks in northern Australia and show that estimates of error in species identifications need to be incorporated into management strategies to ensure successful recovery of the many recently over-fished shark populations.

    AB - Despite the importance of observers to collect data for effective fisheries management worldwide, their species-identification abilities are rarely assessed. Misidentifications could compromise observer data particularly in diverse, multi-species fisheries such as those in the tropics where visual identification is challenging. Here, we provide the first estimates of the ability of scientific observers to identify five species of morphologically similar carcharhinid sharks (Carcharhinus leucas, C. amboinensis, C. tilstoni, C. sorrah and C. brevipinna) in a fishery in northern Australia. We compared observer field identifications of sharks with genetic validation (814. bp mtDNA NADH dehydrogenase subunit 4) to quantify species identification errors. We used binomial generalised linear models to determine the influences of species, gender, total length, and the observer's experience on identification error. We found that identification error (?20%) depended predominately on the species in question (highest error for C. tilstoni). Male sharks were misidentified less frequently than females, and error decreased marginally with increasing total length. Surprisingly, we found no statistical evidence that observer experience influenced identification error. Our results provide the first benchmark of identification accuracy of observers for carcharhinid sharks in northern Australia and show that estimates of error in species identifications need to be incorporated into management strategies to ensure successful recovery of the many recently over-fished shark populations.

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    KW - Carcharhinus

    KW - Carcharhinus amboinensis

    KW - Carcharhinus brevipinna

    KW - Carcharhinus leucas

    KW - Carcharhinus sorrah

    KW - Carcharhinus tilstoni

    KW - Chondrichthyes

    U2 - 10.1016/j.fishres.2012.04.007

    DO - 10.1016/j.fishres.2012.04.007

    M3 - Article

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    SP - 109

    EP - 115

    JO - Fisheries Research

    JF - Fisheries Research

    SN - 0165-7836

    ER -