Pfluger said that even if there were a few still in the river he believed they would not have "any chance to survive".
 
"It is a tragedy, a loss not only for China, but for the entire world."
 
The hunt for the fresh water species of dolphins ended on Wednesday.
 
Baiji facts

One of the world's oldest dolphin species

Believed to have survived unchanged for 25 million years

Navigates by echolocation or sonar-like sounds

Extinction blamed on industrial pollution, boat propellers, fishing nets, dams and reduced prey

Last confirmed sighting in 2004

First large mammal pushed to extinction

There were 13 confirmed sightings during a survey in 1997.
 
Baijis have small eyes and long jaws to navigate through the murky waters of the Yangtze, and is believed to have survived unchanged for 25 million years.
 
Their disappearance have been widely blamed on shipping, pollution, habitat destruction and overfishing.
 
"We have to rethink our fresh water strategies. We have to find a way towards a sustainable way to treat the Yangtze and, of course, the fresh water resources in general," Pfluger said.
 
The Swiss conservationist said that the almost certain loss of the baiji dolphins should be taken as a warning to pursue conservation efforts.
 
The Chinese government had set up a baiji dolphin-breeding reserve in a lake in central Hubei province but failed to find any in the wild.
 
Traditional Chinese thinking of the baiji is as a river goddess.
 
The search, led by the ministry of agriculture, brought together world-class experts from the Swiss Federal Institute of Aquatic Science and Technology, the National Oceanic and Atmospheric Administration, the Hubbs-Seaworld Institute from San Diego and the Fisheries Research Agency in Japan.
 
The six-week expedition comprising ships and 30 scientists, however, did encounter 300 of the Yangtze finless porpoise, which is endangered.

Source: Agencies