The National Geographic Society and China's Yangtze River Fisheries Institute have launched a new search for the Chinese paddlefish, a critically endangered species experts fear may be extinct, a scientist said Wednesday.
Yang Deguo, deputy director of the Chinese institute, said an initial study launched in May had turned up no signs of the fish in the Yangtze's upper reaches.
"We have been trying to catch one for three months with no success," Yang, who is participating in the study, told The Associated Press in a telephone interview.
Experts hoped the discovery of fish would allow for captive breeding, Yang said.
No young Chinese paddlefish have been spotted since 1995, raising fears that dams on the Yangtze River in which it lives may have destroyed the fish's ability to spawn, Zeb Hogan, team leader for the society's Megafishes Project, said in a statement.
"The fear is that these fish may be close to extinction," Hogan said.
As recently as the 1970s, fisherman each year caught hundreds of the fish, which have reportedly reached lengths of 7 meters (23 feet) and weights of up to 454 kilograms (1,000 pounds).
But their numbers crashed after the construction of a massive dam on the Yangtze River in the 1980s, isolating populations of fish from each other, disrupting their life cycles and making spawning impossible. The problem has been further exacerbated by additional dam construction on the Yangtze, blamed for decimating commercial fisheries all along the river and killing off species such as the Yangtze River dolphin.
Experts believe the river's upper reaches hold the best chances of finding live paddlefish because the area holds many deep pools and underwater caves where old fish can hide.
For thousands of years, paddlefish, which are related to sturgeon, traveled the river from their spawning grounds in the upper reaches to forage in the middle and lower parts of the river and sometimes even along the coast where the Yangtze empties into the Pacific Ocean.