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Type: Journal article
Title: Population abundance and apparent survival of the vulnerable whale shark Rhincodon typus in the Seychelles aggregation
Author: Rowat, D.
Speed, C.
Meekan, M.
Gore, M.
Bradshaw, C.
Citation: Oryx: journal of fauna and flora international, 2009; 43(4):591-598
Publisher: Blackwell Science Ltd
Issue Date: 2009
ISSN: 0030-6053
Statement of
David Rowat, Conrad W. Speed, Mark G. Meekan, Mauvis A. Gore and Corey J.A. Bradshaw
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 mark–recapture 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.
Keywords: Capture–mark–recapture
marker tagging
population estimation
resident population
Rhincodon typus
tag loss
transient population
whale shark
Rights: Copyright © Fauna & Flora International 2009
DOI: 10.1017/S0030605309990408
Appears in Collections:Aurora harvest 5
Earth and Environmental Sciences publications
Environment Institute Leaders publications

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