Journal article

Irrawaddy dolphin demography in the Mekong River: an application of mark-resight models

Gerard Edward Ryan, Verne Dove, Fernando Trujillo, Paul F Doherty

Ecosphere | WILEY | Published : 2011

Abstract

Riverine Irrawaddy dolphin populations are critically endangered and much uncertainty exists over the population status in the Mekong River of northeast Cambodia and southern Lao People's Democratic Republic (Lao PDR). We conducted 11 surveys over three years to estimate abundance at each survey as well as survival and the probability of individuals becoming unavailable for detection between surveys. We utilized novel mark-resight estimators to account for the detection process in estimating these parameters. Annual survival was 0.977 (0.040 SE) and movement in (0.060) and out (0.018) of an observable state was low. We estimated abundance at 84.5 (95% CI=77.9-91.2) with little change over ou..

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University of Melbourne Researchers

Grants

Funding Acknowledgements

GER, VD, FT and PFD gratefully acknowledge the support of Gordon Congdon in bringing this project about. Many thanks for organizational support from the WWF Greater Mekong Programme and the assistance of Phay Somany, Richard Zanre, Roger Mollot, Michelle Owen, Dang Thuy Trang, Stuart Chapman, and Seng Teak, cartography from Huy Keavuth, financial support from Petr Obrdlik and Martin Geiger (WWF Germany), Doris Calegari (WWF Switzerland), and Lasse Juul-Olsen (WWF Denmark). We also thank David Anderson, Ken Burnham, Bill Kendall, Brett McClintock, Gary White, and the Wagar 113 Superpopulation for analysis advice. Jeff Laake, Daniel Walsh, Robert L. Brownell, Jr., Randall Reeves, and one anonymous reviewer provided helpful comments on the manuscript. Most of all we are extremely thankful to David Dove, Eng Tong, Hang Sereyvuth, Vixai Inthapaysy, Boungeut Khamphitak, Kim Sokha, Phouthone Kingsada, Bart Kluskens, Leou Theo, Lor Kimsan, Troy Saville, Tan Someth Bunvath, Payou Thammavongseng, Theng Lipine, Vinn Bunna, and many others for sweating out long, hot hours in the field, and the wonderful Cambodian families who shelter and feed us all along the river. Finally, we appreciate the support from Cambodian Government in this work.