"Rescue comes too late as Yangtze River dolphin declared extinct... A FRESHWATER dolphin species has been declared extinct after desperate efforts to rescue it came too late. One British zoologist yesterday described the loss of the Yangtze River dolphin as a "shocking tragedy". It is the first extinction of a large vertebrate for more than 50 years. Experts say human activity killed off the white long-beaked dolphin, which grew to eight feet and weighed 500lb. The animal is the first cetacean, the group that includes whales and porpoises, to vanish as a direct result of human influence.