Scarring patterns and relative mortality rates of Indian Ocean whale sharks

Conrad Speed, M Meekan, D ROWAT, S Pierce, A Marshall, Corey Bradshaw

    Research output: Contribution to journalArticleResearchpeer-review

    Abstract

    This study recorded the scarring rate and severity for whale sharks Rhincodon typus from three Indian Ocean aggregations (Australia, Seychelles and Mozambique), and examined whether scarring (mostly attributed to boat strikes and predator attacks) influences apparent survival rates using photo-identification libraries. Identifications were based on spot-and-stripe patterns that are unique to individual whale sharks. Scarring was most prevalent in the Seychelles aggregation (67% of individuals). Predator bites were the most frequent source of scarring (aside from minor nicks and abrasions) and 27% of individuals had scars consistent with predator attacks. A similar proportion of whale sharks had blunt trauma, laceration and amputation scars, the majority of which appeared to be caused by ship collisions. Predator bites were more common (44% of individuals) and scars from ship collisions were less common at Ningaloo Reef than at the other two locations (probability of among-site differences occurring randomly = 0.0007 based on a randomized multinomial contingency analysis). In all aggregations, scars occurred most often on the caudal fin, which may result from the fin being the body part closest to the surface when boats pass over, or they may provide a large target for predator attack. No evidence was found for an effect of scarring on apparent survival (?; mean � s.e.) for the Ningaloo (not scarred ? = 0.858 � 0.033; scarred ? = 0.929 � 0.033) or Seychelles populations (not scarred ? = 0.502 � 0.060; scarred ? = 0.538 � 0.070). The lower apparent survival of the Seychelles population may be attributed to a high number of transient whale sharks in this aggregation that might bias estimates. This study indicates that while scarring from natural predators and smaller vessels appears to be unrelated to whale shark survival, the effect of deaths related to ship strike need to be quantified to assist in future management of this species. � 2008 The Authors.
    Original languageEnglish
    Pages (from-to)1488-1503
    Number of pages16
    JournalJournal of Fish Biology
    Volume72
    Issue number6
    Publication statusPublished - 2008

    Fingerprint

    shark
    Indian Ocean
    whale
    Seychelles
    predator
    predators
    mortality
    ships
    boats
    fins
    collision
    lacerations
    amputation
    Mozambique
    abrasion
    Rhincodon typus
    reefs
    reef
    vessel
    survival rate

    Cite this

    Speed, C., Meekan, M., ROWAT, D., Pierce, S., Marshall, A., & Bradshaw, C. (2008). Scarring patterns and relative mortality rates of Indian Ocean whale sharks. Journal of Fish Biology, 72(6), 1488-1503.
    Speed, Conrad ; Meekan, M ; ROWAT, D ; Pierce, S ; Marshall, A ; Bradshaw, Corey. / Scarring patterns and relative mortality rates of Indian Ocean whale sharks. In: Journal of Fish Biology. 2008 ; Vol. 72, No. 6. pp. 1488-1503.
    @article{b33c064278414ff5a39e923fea915254,
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    abstract = "This study recorded the scarring rate and severity for whale sharks Rhincodon typus from three Indian Ocean aggregations (Australia, Seychelles and Mozambique), and examined whether scarring (mostly attributed to boat strikes and predator attacks) influences apparent survival rates using photo-identification libraries. Identifications were based on spot-and-stripe patterns that are unique to individual whale sharks. Scarring was most prevalent in the Seychelles aggregation (67{\%} of individuals). Predator bites were the most frequent source of scarring (aside from minor nicks and abrasions) and 27{\%} of individuals had scars consistent with predator attacks. A similar proportion of whale sharks had blunt trauma, laceration and amputation scars, the majority of which appeared to be caused by ship collisions. Predator bites were more common (44{\%} of individuals) and scars from ship collisions were less common at Ningaloo Reef than at the other two locations (probability of among-site differences occurring randomly = 0.0007 based on a randomized multinomial contingency analysis). In all aggregations, scars occurred most often on the caudal fin, which may result from the fin being the body part closest to the surface when boats pass over, or they may provide a large target for predator attack. No evidence was found for an effect of scarring on apparent survival (?; mean � s.e.) for the Ningaloo (not scarred ? = 0.858 � 0.033; scarred ? = 0.929 � 0.033) or Seychelles populations (not scarred ? = 0.502 � 0.060; scarred ? = 0.538 � 0.070). The lower apparent survival of the Seychelles population may be attributed to a high number of transient whale sharks in this aggregation that might bias estimates. This study indicates that while scarring from natural predators and smaller vessels appears to be unrelated to whale shark survival, the effect of deaths related to ship strike need to be quantified to assist in future management of this species. � 2008 The Authors.",
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    author = "Conrad Speed and M Meekan and D ROWAT and S Pierce and A Marshall and Corey Bradshaw",
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    Speed, C, Meekan, M, ROWAT, D, Pierce, S, Marshall, A & Bradshaw, C 2008, 'Scarring patterns and relative mortality rates of Indian Ocean whale sharks', Journal of Fish Biology, vol. 72, no. 6, pp. 1488-1503.

    Scarring patterns and relative mortality rates of Indian Ocean whale sharks. / Speed, Conrad; Meekan, M; ROWAT, D; Pierce, S; Marshall, A; Bradshaw, Corey.

    In: Journal of Fish Biology, Vol. 72, No. 6, 2008, p. 1488-1503.

    Research output: Contribution to journalArticleResearchpeer-review

    TY - JOUR

    T1 - Scarring patterns and relative mortality rates of Indian Ocean whale sharks

    AU - Speed, Conrad

    AU - Meekan, M

    AU - ROWAT, D

    AU - Pierce, S

    AU - Marshall, A

    AU - Bradshaw, Corey

    PY - 2008

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    N2 - This study recorded the scarring rate and severity for whale sharks Rhincodon typus from three Indian Ocean aggregations (Australia, Seychelles and Mozambique), and examined whether scarring (mostly attributed to boat strikes and predator attacks) influences apparent survival rates using photo-identification libraries. Identifications were based on spot-and-stripe patterns that are unique to individual whale sharks. Scarring was most prevalent in the Seychelles aggregation (67% of individuals). Predator bites were the most frequent source of scarring (aside from minor nicks and abrasions) and 27% of individuals had scars consistent with predator attacks. A similar proportion of whale sharks had blunt trauma, laceration and amputation scars, the majority of which appeared to be caused by ship collisions. Predator bites were more common (44% of individuals) and scars from ship collisions were less common at Ningaloo Reef than at the other two locations (probability of among-site differences occurring randomly = 0.0007 based on a randomized multinomial contingency analysis). In all aggregations, scars occurred most often on the caudal fin, which may result from the fin being the body part closest to the surface when boats pass over, or they may provide a large target for predator attack. No evidence was found for an effect of scarring on apparent survival (?; mean � s.e.) for the Ningaloo (not scarred ? = 0.858 � 0.033; scarred ? = 0.929 � 0.033) or Seychelles populations (not scarred ? = 0.502 � 0.060; scarred ? = 0.538 � 0.070). The lower apparent survival of the Seychelles population may be attributed to a high number of transient whale sharks in this aggregation that might bias estimates. This study indicates that while scarring from natural predators and smaller vessels appears to be unrelated to whale shark survival, the effect of deaths related to ship strike need to be quantified to assist in future management of this species. � 2008 The Authors.

    AB - This study recorded the scarring rate and severity for whale sharks Rhincodon typus from three Indian Ocean aggregations (Australia, Seychelles and Mozambique), and examined whether scarring (mostly attributed to boat strikes and predator attacks) influences apparent survival rates using photo-identification libraries. Identifications were based on spot-and-stripe patterns that are unique to individual whale sharks. Scarring was most prevalent in the Seychelles aggregation (67% of individuals). Predator bites were the most frequent source of scarring (aside from minor nicks and abrasions) and 27% of individuals had scars consistent with predator attacks. A similar proportion of whale sharks had blunt trauma, laceration and amputation scars, the majority of which appeared to be caused by ship collisions. Predator bites were more common (44% of individuals) and scars from ship collisions were less common at Ningaloo Reef than at the other two locations (probability of among-site differences occurring randomly = 0.0007 based on a randomized multinomial contingency analysis). In all aggregations, scars occurred most often on the caudal fin, which may result from the fin being the body part closest to the surface when boats pass over, or they may provide a large target for predator attack. No evidence was found for an effect of scarring on apparent survival (?; mean � s.e.) for the Ningaloo (not scarred ? = 0.858 � 0.033; scarred ? = 0.929 � 0.033) or Seychelles populations (not scarred ? = 0.502 � 0.060; scarred ? = 0.538 � 0.070). The lower apparent survival of the Seychelles population may be attributed to a high number of transient whale sharks in this aggregation that might bias estimates. This study indicates that while scarring from natural predators and smaller vessels appears to be unrelated to whale shark survival, the effect of deaths related to ship strike need to be quantified to assist in future management of this species. � 2008 The Authors.

    KW - Cetacea

    KW - Chondrichthyes

    KW - Rhincodon typus

    KW - Rhincodontidae

    M3 - Article

    VL - 72

    SP - 1488

    EP - 1503

    JO - Journal of Fish Biology

    JF - Journal of Fish Biology

    SN - 0022-1112

    IS - 6

    ER -

    Speed C, Meekan M, ROWAT D, Pierce S, Marshall A, Bradshaw C. Scarring patterns and relative mortality rates of Indian Ocean whale sharks. Journal of Fish Biology. 2008;72(6):1488-1503.