HONG KONG (Reuters) - A paint chemical that is widely used in China is leaking into the Yangtze river and may be responsible for deformities and decreasing numbers of rare wild Chinese sturgeon, a study has found.
In an article published in the Proceedings of the National Academy of Sciences, researchers said a significant proportion of juvenile sturgeon caught at the river had either one or no eyes, or had misshapen skeletons.
Chinese sturgeon, which have existed on earth for 140 million years, are among the first class of protected animals in China. The slow-growing fish has an increased capacity to accumulate the paint chemical triphenyltin (TPT), which contains tin.
The experts collected two- and three-day old Chinese sturgeon larvae from a spawning area below the Gezhouba Dam, which is 38 km (24 miles) downstream from the Three Gorges Dam on the Yangtze River.
They later hatched in a laboratory in Jingzhou city in central Hubei province where 6.3 percent were found with skeletal deformities and 1.2 percent had either no eyes or just one eye.
“Maternal transfer of TPT ... in eggs of wild Chinese sturgeon poses a significant risk to the larvae naturally fertilized or hatched in the Yangtze River,” wrote the researchers, led by Hu Jiangying at the College of Urban and Environmental Sciences at Beijing University.
TPT is extensively used in paints to prevent the fouling of ship hulls and fishing nets. It is also used in fungicide to treat crops in China. A derivative of TPT is also used to eliminate snails in paddy fields.
Earlier studies attributed the steep decline in Chinese sturgeon numbers to loss of spawning habitat because of the construction of the Three Gorges Dam and Gezhouba Dam.
In this study, two adult males and two adult females of the Chinese sturgeon were also captured from the Yangtze River for artificial propagation and 3.9 percent of the juveniles were later observed to have malformed skeletons, while 1.7 percent had one or no eyes.
Subjecting their study to more robust testing, the researchers injected TPT into batches of eggs of the Chinese sturgeon and Siberian sturgeon.
“Experimental exposure of Chinese and Siberian sturgeon (eggs) to elevated TPT levels resulted in an increase in the occurrence of deformities, the rates of which were consistent with those seen in wild populations exposed to similar concentrations of the compound,” they wrote.
“Together, these multiple lines of evidence were consistent with the hypothesis that TPT was the likely cause of the malformations observed in larvae of wild Chinese sturgeon, although other contaminants may be present that could produce similar effects.”
Editing by Jeremy Laurence