Population abundance and apparent survival of the Vulnerable whale shark Rhincodon typus in the Seychelles aggregation

D ROWAT, C SPEED, Mark Meekan, M GORE, Corey Bradshaw

    Research output: Contribution to journalArticleResearchpeer-review

    Abstract

    Identifying individuals through time can provide information on population size, composition, survival and growth rates. Identification using photographs of distinctive physical characteristics has been used in many species to replace conventional marker tagging. We evaluated photographic records over 7 years of Vulnerable whale sharks Rhincodon typus, at an aggregation in the Seychelles, for estimation of population size and structure. We collected 11,681 photographs of which only 1,149 were suitable for comparison using semi-automated matching software (I3S) of individual spot patterns behind the gills. Photo-identification showed that there was considerable loss of marker tags and enabled an estimation of the rate of tag loss. The combination of photo-identification with marker tagging identified a total of 512 individual sharks over 2001-2007. Of these, there were 115 resightings in subsequent years with two sharks identified in 2001 resighted 5 years later in 2006 and another shark sighted in 2001 resighted in 2007. Estimates of abundance using conventional open markrecapture models for 2004-2007 were 348-488 sharks (95% confidence interval), with a high level of entry into the population by itinerants. Annual apparent survival probability was 0.343-0.781 over 2004-2007, with an average annual recapture probability of 0.201. These results are the first to suggest a highly transient population of whale sharks around the Seychelles, indicating that international or at least regional-scale conservation approaches are required. � 2009 Fauna & Flora International.
    Original languageEnglish
    Pages (from-to)591-598
    Number of pages8
    JournalOryx
    Volume43
    Publication statusPublished - 2009

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    Seychelles
    shark
    sharks
    whale
    photographs
    population size
    tagging
    photograph
    confidence interval
    gills
    population structure
    flora
    fauna
    Rhincodon typus
    software
    marker

    Cite this

    ROWAT, D., SPEED, C., Meekan, M., GORE, M., & Bradshaw, C. (2009). Population abundance and apparent survival of the Vulnerable whale shark Rhincodon typus in the Seychelles aggregation. Oryx, 43, 591-598.
    ROWAT, D ; SPEED, C ; Meekan, Mark ; GORE, M ; Bradshaw, Corey. / Population abundance and apparent survival of the Vulnerable whale shark Rhincodon typus in the Seychelles aggregation. In: Oryx. 2009 ; Vol. 43. pp. 591-598.
    @article{1c24ca7135b84ad09351b2efe5753475,
    title = "Population abundance and apparent survival of the Vulnerable whale shark Rhincodon typus in the Seychelles aggregation",
    abstract = "Identifying individuals through time can provide information on population size, composition, survival and growth rates. Identification using photographs of distinctive physical characteristics has been used in many species to replace conventional marker tagging. We evaluated photographic records over 7 years of Vulnerable whale sharks Rhincodon typus, at an aggregation in the Seychelles, for estimation of population size and structure. We collected 11,681 photographs of which only 1,149 were suitable for comparison using semi-automated matching software (I3S) of individual spot patterns behind the gills. Photo-identification showed that there was considerable loss of marker tags and enabled an estimation of the rate of tag loss. The combination of photo-identification with marker tagging identified a total of 512 individual sharks over 2001-2007. Of these, there were 115 resightings in subsequent years with two sharks identified in 2001 resighted 5 years later in 2006 and another shark sighted in 2001 resighted in 2007. Estimates of abundance using conventional open markrecapture models for 2004-2007 were 348-488 sharks (95{\%} confidence interval), with a high level of entry into the population by itinerants. Annual apparent survival probability was 0.343-0.781 over 2004-2007, with an average annual recapture probability of 0.201. These results are the first to suggest a highly transient population of whale sharks around the Seychelles, indicating that international or at least regional-scale conservation approaches are required. � 2009 Fauna & Flora International.",
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    author = "D ROWAT and C SPEED and Mark Meekan and M GORE and Corey Bradshaw",
    year = "2009",
    language = "English",
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    pages = "591--598",
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    ROWAT, D, SPEED, C, Meekan, M, GORE, M & Bradshaw, C 2009, 'Population abundance and apparent survival of the Vulnerable whale shark Rhincodon typus in the Seychelles aggregation', Oryx, vol. 43, pp. 591-598.

    Population abundance and apparent survival of the Vulnerable whale shark Rhincodon typus in the Seychelles aggregation. / ROWAT, D; SPEED, C; Meekan, Mark; GORE, M; Bradshaw, Corey.

    In: Oryx, Vol. 43, 2009, p. 591-598.

    Research output: Contribution to journalArticleResearchpeer-review

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    T1 - Population abundance and apparent survival of the Vulnerable whale shark Rhincodon typus in the Seychelles aggregation

    AU - ROWAT, D

    AU - SPEED, C

    AU - Meekan, Mark

    AU - GORE, M

    AU - Bradshaw, Corey

    PY - 2009

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    N2 - Identifying individuals through time can provide information on population size, composition, survival and growth rates. Identification using photographs of distinctive physical characteristics has been used in many species to replace conventional marker tagging. We evaluated photographic records over 7 years of Vulnerable whale sharks Rhincodon typus, at an aggregation in the Seychelles, for estimation of population size and structure. We collected 11,681 photographs of which only 1,149 were suitable for comparison using semi-automated matching software (I3S) of individual spot patterns behind the gills. Photo-identification showed that there was considerable loss of marker tags and enabled an estimation of the rate of tag loss. The combination of photo-identification with marker tagging identified a total of 512 individual sharks over 2001-2007. Of these, there were 115 resightings in subsequent years with two sharks identified in 2001 resighted 5 years later in 2006 and another shark sighted in 2001 resighted in 2007. Estimates of abundance using conventional open markrecapture models for 2004-2007 were 348-488 sharks (95% confidence interval), with a high level of entry into the population by itinerants. Annual apparent survival probability was 0.343-0.781 over 2004-2007, with an average annual recapture probability of 0.201. These results are the first to suggest a highly transient population of whale sharks around the Seychelles, indicating that international or at least regional-scale conservation approaches are required. � 2009 Fauna & Flora International.

    AB - Identifying individuals through time can provide information on population size, composition, survival and growth rates. Identification using photographs of distinctive physical characteristics has been used in many species to replace conventional marker tagging. We evaluated photographic records over 7 years of Vulnerable whale sharks Rhincodon typus, at an aggregation in the Seychelles, for estimation of population size and structure. We collected 11,681 photographs of which only 1,149 were suitable for comparison using semi-automated matching software (I3S) of individual spot patterns behind the gills. Photo-identification showed that there was considerable loss of marker tags and enabled an estimation of the rate of tag loss. The combination of photo-identification with marker tagging identified a total of 512 individual sharks over 2001-2007. Of these, there were 115 resightings in subsequent years with two sharks identified in 2001 resighted 5 years later in 2006 and another shark sighted in 2001 resighted in 2007. Estimates of abundance using conventional open markrecapture models for 2004-2007 were 348-488 sharks (95% confidence interval), with a high level of entry into the population by itinerants. Annual apparent survival probability was 0.343-0.781 over 2004-2007, with an average annual recapture probability of 0.201. These results are the first to suggest a highly transient population of whale sharks around the Seychelles, indicating that international or at least regional-scale conservation approaches are required. � 2009 Fauna & Flora International.

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    KW - growth rate

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    KW - population structure

    KW - shark

    KW - software

    KW - survival

    KW - tagging

    KW - temporal analysis

    KW - Seychelles

    KW - Cetacea

    KW - Chondrichthyes

    KW - Rhincodon typus

    KW - Rhincodontidae

    M3 - Article

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    JO - Oryx

    JF - Oryx

    SN - 0030-6053

    ER -