AsianScientist (Nov. 9, 2018) – A research group in China has found that the damming of the Yangtze River has had severe consequences on the lifecycle of the critically endangered Chinese sturgeon. They reported their findings in Current Biology.
Before the damming of the Yangtze River in 1981, Chinese sturgeon swam freely each summer into the river’s mouth, continuing upriver while fasting along the way. The fish bred in the upper spawning ground the following fall before returning quickly to the sea thereafter. With the construction of dams along the Yangtze River, the route that the sturgeons can take has been irrevocably altered.
In this study, researchers led by Professor Huang Zhenli of the China Institute of Water Resources and Hydropower Research demonstrated that since 1981, the Gezhouba Dam has reduced the distance of the Chinese sturgeon’s migration by 1,175 kilometers. As a result, the fish reach reproductive maturity more than a month (37 days) later.
The delayed maturity has in turn reduced the effective population size as there are fewer breeding individuals. The environmental capacity of the new spawning ground has also been reduced by almost a quarter. The building of subsequent dams in the last ten years has further led to an increase in water temperature, which is known to discourage spawning.
The researchers reported that dams have caused the number of adult sturgeon in the Yangtze River and the sea to be reduced from more than 32,000 before 1981 to 6,000 in 2010, and about 2,500 in 2015. At this rate, the researchers predict that the natural population of Chinese sturgeon will go extinct as soon as the next decade.
“The protection of the wild Chinese sturgeon requires effective measures taken immediately,” said the researchers. “Artificial restocking, which China has been doing without maintaining breeding activity, is inadequate and unsustainable.”
Despite the poor outlook for the Chinese sturgeon, the researchers reserve hope that their findings will lead to targeted measures to maintain the wild population of the endangered species of fish. They say that lowering the water temperature to a suitable range of 18°C-20°C during the breeding season is a top priority. They are now working on a follow-up study to explore the dams’ effects on the more complex migration of young sturgeon.
The scientists also noted that their findings are not unique to the Yangtze River. Most of the world’s rivers have been dammed, and those dams have long been considered a serious threat to migratory fish. Hence, the framework used in this study may be useful to examine the impact of dams on other fish populations.
The article can be found at: Huang & Wang (2018) Yangtze Dams Increasingly Threaten the Survival of the Chinese Sturgeon.
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Source: Cell Press; Photo: Pixabay.
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