MEPS 319:275-285 (2006)  -  doi:10.3354/meps319275

Population size and structure of whale sharks Rhincodon typus at Ningaloo Reef, Western Australia

Mark G. Meekan1,*, Corey J. A. Bradshaw2, Michelle Press3, Cary McLean4, Allison Richards5, Suzy Quasnichka6, J. Geoff Taylor7

1Australian Institute of Marine Science, PO Box 40197, Casuarina MC, Northern Territory 0811, Australia
2School for Environmental Research, Institute of Advanced Studies, Charles Darwin University, Darwin, Northern Territory 0909, Australia
3School of Science and Primary Industries, Charles Darwin University, Darwin, Northern Territory 0909, Australia
4Australian Institute of Marine Science, PMB 3, Townsville MC, Queensland 4810, Australia
5PO Box 293, Exmouth, Western Australia 6707, Australia
6Iambic Productions, 89 Whiteladies Road, Clifton BS8 2NT, UK
7PO Box 126, Busselton, Western Australia 6280, Australia

ABSTRACT: We used photo-identification to produce estimates of population size and structure of whale sharks Rhincodon typus at Ningaloo Reef, Western Australia. We analysed photographs of whale sharks taken from 1992 to 2004. A combination of spot and stripe patterns behind the last gill slit and forward of the dorsal fin (lateral view), and distinctive scars and marks on the body and fins were useful for identifying individual sharks. These patterns appeared to be unique to individuals and distinctive markings could be recognized on some sharks for more than a decade. From 581 photographs, 159 individuals were identified. Of these, 74% were male, 16% were female and 10% were of indeterminate gender. Photographed sharks ranged in estimated size from 3 to 10 m total length (TL). The size distribution of sharks was bimodal with a large peak at 8 m and a smaller peak at 6 m TL. Sixty individuals were resighted during the study. Of these, 46 were resighted at different times during the same year (sometimes on multiple occasions) up to 4 mo after they were initially photographed, and 33 were resighted (4 on >2 occasions) in different years. The interval between inter-annual resightings was typically 1 to 3 yr; however, 2 sharks were resighted after a period of 12 yr. We estimated the super population of whale sharks that visit Ningaloo Reef to consist of approximately 300 to 500 individuals (95% confidence interval) based on closed population models, or 320 to 440 based on Jolly-Seber open-population models. Our study shows that photo-identification offers a practical, non-invasive and non-destructive means to obtain data on the population size and demography of whale sharks.


KEY WORDS: Abundance · Cormack-Jolly-Seber models · Lincoln-Peterson estimator · Mark-recapture models · Photo-identification · Program MARK · Sex ratio · Whale shark


Full text in pdf format 
Export citation: Endnote - Reference Manager
Mail this link - Contents Mailing Lists - RSS
- -