The already rare Chinese sturgeon is teetering on the brink of extinction since the fish didn't reproduce this year for the first time on record.

Formerly plentiful in the Yangtze River, the fish are described as "weighing from 500 to 700 pounds." Their population has sharply declined due to pollution and changes to the fish's habitat as well as decades of overfishing, the New York Times reported.

"It is the first time that we found no natural reproduction of the endangered sturgeons since records began 32 years ago, when a dam was built," Wei Qiwei, lead researcher of a recent study of the sturgeon, told China's state news agency Xinhua.

No Chinese sturgeon eggs were discovered downstream from the Gezhou Dam from Oct. 31 to Dec. 28 last year, Xinhua reported.

Only about 100 Chinese sturgeon are living in the Yangtze today, Wei told Xinhua.

The few surviving Chinese sturgeon have likely been sustained by artificial breeding alone, according to the new survey from the Chinese Academy of Fishery Sciences.

The sturgeon, which is scaleless and characterized by bony plates in front of its mouth, has been peculiarly vulnerable to adverse environmental changes such as overfishing and polluting because it is slow to reach maturity.

Around 10,000 Chinese sturgeon were estimated to be in the Yangtze River in the 1970s, but the number fell to fewer than 300 by 2007.

Besides poor fishing regulations and pollution, Chinese sturgeon have reportedly declined because of dams built along the river that have interrupted the fish's migrating pattern and cut its breeding ground from 350 miles of river to four.

Chinese researchers say the only way to save the species is through conservation efforts such as artificial breeding.

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