Cause of declining sturgeon numbers discovered


For over 20 years the Pallid Sturgeon has been listed as an endangered species, but until this year no one knew why.

The Pallid Sturgeon is a prehistoric fish considered to be part of a 60 million year old species. Today the Pallid Sturgeon is a native of the Missouri and Yellowstone rivers.

An act allowing dams to be built on the Missouri river was passed in 1940.  Soon baby Pallid Sturgeon were no longer present in the water surrounding the dams. Researchers suggested the shorter stretches of river created by the dams were causing the death of the fish, but no one understood why.

Chris Guy, a professor of fisheries science at Montana State University, and a team of researchers set out to investigate the disappearance.

They found that when the fish spawn and their eggs hatch the larva float 310 miles downstream to the spawning area before settling to the bottom of the river. However, dams are less than 310 miles apart, causing the larva to get caught in the headwaters of the dams and reservoirs.

Guy recently discovered that the headwaters near the dams have no oxygen, creating a “dead zone causing baby sturgeon to die. Therefore, sturgeon numbers have declined rapidly in the past 70 years.

“The dilemma is that the dams benefit society tremendously by providing large amounts of electricity and water,” Guy said. “Yet because of them this prehistoric species is declining rapidly.”

Due to the research of Guy and his team, the Army Corps of Engineers – who manage all the dams on the Missouri river – is looking into options to preserve the Pallid Sturgeon.

“The Army Corp. of Engineers has been put under a lot of pressure to utilize different options to allow the larva to float past the headwaters and out of the dead zone,” said Guy.

Options such as lowering the reservoirs to allow larva to float past the headwaters, or somehow creating warmer waters further from the dams to encourage the fish to spawn in a different area have been suggested.

The question is, “How can we convince fish to spawn further upstream?” Guy said. “It’s not likely.”

Despite the obstacles, Guy strongly believes the sturgeon need to be saved.

“The extinction of the Pallid Sturgeon wouldn’t have a great effect on the ecology of the river or the ecosystem, but the Pallid Sturgeon does have a large intrinsic value,” said Guy. “I mean, it’s a dinosaur basically.It’s 60 million years old.”



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