Yangtze dams put endangered sturgeon's future in doubt

November 01, 2018

Before the damming of the Yangtze River in 1981, Chinese sturgeon swam freely each summer one after another into the river's mouth, continuing upriver while fasting all along the way. They bred in the upper spawning ground the following fall before returning quickly back to the sea. Now, researchers reporting in Current Biology on November 1 offer new insight into the threat the dams have since posed to the critically endangered fish.

"We have established a novel theoretical framework to study the relationship between dams and the fish and to reveal the quantitative mechanism by which dams impact anadromous fish," says Zhenli Huang of the China Institute of Water Resources and Hydropower Research. "We have found that the loss of effective breeding and environmental capacity are two crucial factors resulting in an ongoing decline in adult abundances of Chinese sturgeon in the Yangtze River."

The findings likely aren't unique to the Yangtze River, the researchers note. Most of the world's rivers have been dammed. Those dams have long been considered a serious threat to migratory fish around the world. But, scientists hadn't documented all of the ways in which dams affect fish.

To explore in the new study, Huang and study co-author Luhai Wang combined field observations with theoretical analysis of historical data. They wanted to understand something that had already become clear: why the spawning activity of Chinese sturgeon had become more and more difficult to observe in recent years.

The study shows 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. That's because the flow of water as fish swim upstream during migration is an important factor influencing sexual maturity.

That 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, perhaps by almost a quarter. The building of subsequent dams in the last 10 years has also led to an increase in water temperature, which is known to discourage spawning.

Overall, the researchers report that the cascade dams have led to an ongoing decline in the number of adult sturgeon in the Yangtze River and the sea from more than 32,000 before 1981, to 6,000 in 2010, and about 2,500 in 2015. At this rate, they predict, the natural population of Chinese sturgeon will go extinct, perhaps as soon as the next decade.

"The protection of the wild Chinese sturgeon requires effective measures taken immediately," the researchers write. "Artificial restocking, which China has been doing without maintaining breeding activity, is inadequate and unsustainable."

Despite a poor outlook for Chinese sturgeon, the researchers reserve hope that their findings will lead to targeted measures in order to maintain the wild population of endangered species of fish at an appropriate level. They say that lowering the water temperature to a suitable range of 18°C-20°C during the breeding season is undoubtedly the top priority. They're now working on a follow-up study to explore the dams' effects on the more complex migration of young sturgeon.
-end-
This research was supported by the National Natural Science Foundation of China.

Current Biology, Huang and Wang: "Yangtze Dams Increasingly Threaten the Survival of the Chinese Sturgeon" https://www.cell.com/current-biology/fulltext/S0960-9822(18)31227-2

Current Biology (@CurrentBiology), published by Cell Press, is a bimonthly journal that features papers across all areas of biology. Current Biology strives to foster communication across fields of biology, both by publishing important findings of general interest and through highly accessible front matter for non-specialists. Visit: http://www.cell.com/current-biology. To receive Cell Press media alerts, contact press@cell.com.

Cell Press

Related Fish Articles from Brightsurf:

Fish banks
Society will require more food in the coming years to feed a growing population, and seafood will likely make up a significant portion of it.

More than 'just a fish' story
For recreational fishing enthusiasts, the thrill of snagging their next catch comes with discovering what's hooked on the end of the line.

Fish evolution in action: Land fish forced to adapt after leap out of water
Many blennies - a remarkable family of fishes - evolved from an aquatic 'jack of all trades' to a 'master of one' upon the invasion of land, a new study led by UNSW scientists has shown.

How fish got onto land, and stayed there
Research on blennies, a family of fish that have repeatedly left the sea for land, suggests that being a 'jack of all trades' allows species to make the dramatic transition onto land but adapting into a 'master of one' allows them to stay there.

Fish feed foresight
As the world increasingly turns to aqua farming to feed its growing population, there's no better time than now to design an aquaculture system that is sustainable and efficient.

Robo-turtles in fish farms reduce fish stress
Robotic turtles used for salmon farm surveillance could help prevent fish escapes.

Heatwaves risky for fish
A world-first study using sophisticated genetic analysis techniques have found that some fish are better than others at coping with heatwaves.

A new use for museum fish specimens
This paper suggests using museum specimens to estimate the length-weight relationships of fish that are hard to find alive in their natural environment.

Reef fish caring for their young are taken advantage of by other fish
Among birds, the practice of laying eggs in other birds' nests is surprisingly common.

Anemones are friends to fish
Any port in a storm, any anemone for a small fish trying to avoid being a predator's dinner.

Read More: Fish News and Fish Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.