Report Abundance of Mekong Dolphin Population, 2007 | WWF

Report Abundance of Mekong Dolphin Population, 2007

Posted on
20 June 2008

Cambodian Mekong Dolphin Conservation Project (CMDCP) is a collaborative project between WWF, World Conservation Society (WCS), Fisheries Administration and Cambodian Rural Development Team (CRDT).

Each year, the Cambodian Mekong Dolphin Conservation Project conducts a population survey of the Irrawaddy dolphin in Cambodia’s Mekong river. This is done in April and May when the Mekong river is at its lowest and the dolphins are concentrated in and around nine deep pools, making them easier to locate.

There are a number of different methods used to estimate dolphin numbers, choice of method depends on factors such as environmental conditions, dolphin species behaviour and research resources available. Different methods invariably produce different figures. In 2007, CMDCP recruited river dolphin monitoring expert Dr. Fernando Trujillo to evaluate the best method for monitoring dolphins on the Mekong river, between Kratie and Stung Treng Provinces, provide training to the CMDCP research team and supervise the research. Fernando, a recent winner of the prestigious 2007 Whitley Gold Award for conservation, brought with him 20 years research experience on river dolphins.

A sophisticated survey technique based on taking photos of each dolphin sighted and then using the image of the dorsal fin to identify individual dolphins was decided upon. A mathematical equation is then used to estimate dolphin numbers, based on the number of individuals marked (identified) by photography on a first survey and the number recaptured by photography on follow up surveys. Added advantages of this method include the production of a photo ID database of Mekong dolphins, which can be used to improve our understanding of Irrawaddy dolphin ecology in the Mekong by enabling us to monitor distribution, movement and social patterns, as well as future mortality and change in population dynamics.

Our research found that as at the end of May 2007 the preliminary population abundance estimate for the Mekong dolphin was between 66 and 86 dolphins, with a best estimate of 71 dolphins. It is important to note that further population surveys and careful monitoring of mortalities will be important to increase our confidence in the number of dolphins remaining in the Mekong in Cambodia and southern Laos. With more accurate information on the Mekong dolphin population and improved understanding of dolphin ecology, combined with ongoing research into causes of dolphin mortality, conservation partners will be better able to design more effective conservation strategies.

Please download the report for further information on the dolphin population research.
Richard Zanre, freshwater conservation programme manager