Wednesday, December 9, 2015

Zebra mussels in Missouri River dams dooming native fish

Since at least 2004 zebra mussels have been plaguing the main stem dams in the Missouri River. The invasive mussels compete with paddlefish and other native species like the pallid sturgeon.
Mike Smith, a specialist in aquatic invasive species for the state Game, Fish and Parks Department, presented an overview on AIS to the board. Eleven species of fish, seven species of plants and four species of invertebrates such as zebra mussels have been confirmed in South Dakota as invasive, Smith said. There also have been indications of quagga mussels now in South Dakota. With 700,000 zebra mussels possible per square meter, and each filtering a liter of water per day, they can have an enormous effect on water quality and on water intakes, such as for irrigation systems and water treatment, as well as docks and boat facilities in the water, he said. “Eradication is basically unfeasible,” Smith said. The impact on the fishery is difficult to link to zebra mussels, Smith said. The water clarity will increase and the plankton community will be diminished, but there hasn’t been proof linking zebra mussels to a decline in the fishery. “That effect is unknown,” Smith said. Do they have natural predators? “Not in the U.S.,” Smith said. [Bob Mercer]
Lake sturgeon prey on some species of mussels.

Christopher Guy, assistant unit leader with the US Geological Survey Montana Cooperative Fishery Unit and professor at Montana State University, joined Dakota Midday host Karl Gerhke on Bill Janklow's idea of public radio to talk about the importance of recent findings on the endangered pallid sturgeon in the upper Missouri River basin.
According to American Rivers, an advocacy group that tracks U.S. dam removals, 72 dams in 19 states were torn down in 2014, a record. That is roughly double the annual number from 10 years ago. Some 1,185 dams have been removed since 1912, according to the group. The fleet of U.S. dams, however, is still enormous. The Army Corps of Engineers counts at least 87,000 dams in its database. Removing dams produces its own benefits. Public safety is enhanced by reducing the risk of a dam failure, and moribund freshwater fisheries are rejuvenated when a segmented river is reconnected. [Circle of Blue]
Below the Missouri River dams pallid sturgeon are showing signs of recovery but above?

Pallid sturgeon come from a genetic line that has lived on this planet for tens of millions of years; yet it has been decades since anyone has documented any of the enormous fish successfully producing young that survive to adulthood in the upper Missouri River basin. Now, fisheries scientists with the U.S. Geological Survey, Montana State University and the U.S. Fish and Wildlife Service have shown why, detailing for the first time the biological mechanism that has caused the long decline of pallid sturgeon in the Missouri River and led to its being placed on the endangered species list 25 years ago. 
In a paper published this week in the journal Fisheries, the scientists show that oxygen-depleted dead zones between dams in the upper Missouri River are directly linked with the failure of endangered pallid sturgeon hatched embryos to survive to adulthood. Given what the new research shows about how no oxygen is available to hatched pallid sturgeon embryos, the authors of the paper propose that officials will need to consider innovative approaches to managing Missouri River reservoirs for pallid sturgeon conservation to have a chance. [press release, US Geological Survey]
Accumulated mercury in large fish causes spontaneous abortions yet record non-native salmon in Lake Oahe go untested.
Paddlefish feed by filtering microscopic plankton out of the water, so they really aren’t susceptible to traditional fishing practices. They have to be snagged. Because the feed almost exclusively on zooplankton, paddlefish spend a lot of their time near the plankton-rich surface waters of their home river so they can be seen and targeted. Still, snagging a paddlefish is only feasible if the fish gather in large numbers, Pierce said. Otherwise it’s like finding a needle in a haystack the size of Rhode Island. [Pierre Capital Journal]
President Obama: decertify the dinosaurs that are the main stem dams, tear them down and rewild the West.

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