Existing at the edge of extinction, these sturgeon live in the East China and Yellow seas and return to China's Yangtze River to spawn.
Construction of dams on the river is thought to have contributed to a decline in the species, and an artificial propagation effort has not resulted in recovery of the fish.
In addition, increasing numbers of the fish are being reported with deformed skeletons or one or no eyes, researchers report in Tuesday's edition of Proceedings of the National Academy of Sciences.
They also found that the female to male sex ratio of the Chinese sturgeon was 0.79 to 1 in 1981-1993, but in 2003-2004 was 5.9 to 1, and the males' sperm was less active.
The research team led by Jianying Hu of Peking University in Beijing, China, noted that the spawning fish are exposed to concentrations of synthetic chemicals including triphenyltin, which is used in marine paints to prevent growth on ship hulls and fishnets.
TPT, which is also used in some pesticides, is known to cause eye and shape malformations in other fish, so the researchers tested the sturgeon and found it concentrated in high quantities in them.
Because of the protected status of Chinese sturgeon the researchers were able to obtain only 80 eggs for testing, but they also tested the effects of injecting TPT into the eggs of Siberian sturgeon and they found malformation rates similar to those of wild Chinese sturgeon.
They concluded that "TPT was the most likely cause of the deformities."
The research was funded by the National Natural Science Foundation of China, National Basic Research Program of China, Fund of Three-Gorges Project, University of Hong Kong and National Science and Engineering Research Council of Canada.
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