WASHINGTON, DC, August 16, 2011 – Irrawaddy dolphin numbers have declined to just 85 in Southeast Asia’s Mekong River, leading researchers to conclude that the population is at high risk of extinction, a new World Wildlife Fund (WWF) survey revealed. One big factor in the decline is that dolphin calf survival is extremely low.
“Evidence is strong that very few young animals survive to adulthood, as older dolphins die off and are not replaced,” said Dr. Li Lifeng, Director of WWF’s Freshwater Program.
The research is based on photographic identification of the critically endangered dolphins through unique markings on their dorsal fins. This method is called photographic mark-recapture, and similar methods are used for surveys of other species including whales, tigers and leopards.
The current findings are higher than previous population estimates of the Irrawaddy dolphin, and scientists say that this is not because there are more dolphins, but because of advances in the surveying process. “With a larger dataset and recent analytical advances, previously unidentifiable dolphins which had few marks on their dorsal fins have been included,” Dr. Li explained.
Three populations of Irrawaddy river dolphins exist -- in the Mekong River, the Irrawaddy River in Myanmar, and the Mahakam River in Indonesia. The survey only covered the Mekong population, but all three populations are critically endangered, and continue to be threatened by gill net entanglement. The causes of calf mortality, however, remain unclear.
“These dolphins are at high risk of extinction by their small population size alone,” said Barney Long, WWF’s Asian Species Expert. “With the added threats of gill net entanglement and high calf mortality, we are seriously concerned about their future.”
The Irrawaddy dolphin is regarded as a sacred animal by both Khmer and Lao people, and is an important source of income and jobs for communities involved in dolphin-watching ecotourism initiatives.
One part of the population surveyed was found on the Cambodia-Lao PDR border of the Mekong River, and numbered only 7 or 8 individuals, emphasizing the need for countries to work collaboratively to protect these incredible animals.
“Our best chance of saving these dolphins from extinction in the Mekong River is through joint conservation action,” said Rebecca Ng, head of WWF’s Mekong program. “WWF is committed to working with the Fisheries Administration, the Dolphin Commission, and communities all along the river to reverse the decline and ensure the survival of this beautiful species.”