A leading biologist is warning that the Mekong River's Irrawaddy dolphins face extinction because of various threats.

Isabel Beasley of the Mekong Dolphin Conservation Project says thousands of Irrawaddy dolphins used to swim the Mekong River, which passes through Tibet, China, Burma, Thailand, Cambodia, Laos and Vietnam.

But Ms. Beasley says a rise in tourism along the Mekong, along with habitat destruction and fishing, has resulted in a severe drop in the dolphin population. She says fewer than 100 Irrawaddy dolphins now live in the Mekong.

She called for immediate measures to be taken to protect the dolphins.