The monster fish, one of the largest freshwater species in the world with lengths up to 23 feet, was once common in China’s Yangtze River. Due to its speed it was commonly referred to in China as the “water tiger.”

Study leader Qiwei Wei of the Chinese Academy of Fishery Sciences called it “a reprehensible and an irreparable loss.”

Zeb Hogan, a fish expert at the University of Nevada, Reno, told National Geographic that it was “very sad” to see the “definitive loss of a very unique and extraordinary animal, with no hope of recovery.”

According to the researchers, no giant paddlefish have been sighted in the Yangtze since 2003, and there are none in captivity. They estimate that the last of the fish likely died between 2005 and 2010.

The species had been deemed “functionally extinct,” or unable to reproduce enough to maintain itself, since 1993.

The main causes of the ancient species’ demise have been listed as over-fishing and the construction of a major dam in 1981 that split the Yangtze, and the Chinese paddlefish population along with it, in two.

The 3,900 mile Yangtze River ecosystem has seen half of the 175 species unique to its waters go extinct, according to Chinese media.

Two other species native to the river have also been declared functionally extinct: the reeves shad and the Yangtze dolphin.

Last week China announced a 10-year fishing ban on some areas of the Yangtze in a bid to protect its beleaguered biodiversity.