TWIN FALLS, Idaho — Treatment is now flowing into the mid-Snake River to kill off invasive quagga mussels that could cause a potential crisis - but that treatment is also likely to kill other things in the river.
The Idaho State Department of Agriculture started the aggressive treatment method on Tuesday, placing metered boxes with the treatment at key mix points along the Snake River from the Twin Falls Dam to Centennial Waterfront Park.
There are multiple state agencies that are part of Idaho's first-ever rapid response plan to eradicate the mussels. Idaho Fish and Game (IDFG) is monitoring the potential fish mortality from this treatment.
"At this point, we are expecting some significant fish loss," said Mike Peterson, the Magic Valley regional fisheries manager for IDFG. "What that will truly look like is still yet to be determined."
The copper-based treatment called "Natrix" being used to eradicate quagga mussels will not poison the fish in the river, and the formula won't be absorbed into their mussel tissue. Instead, it prevents the fish from being able to take oxygen out of the water and into their bloodstream.
"The chemical binds to the oxygen receptors on the gills," Peterson said. "So, if these fish sense it, they can potentially migrate down river."
Before the treatment started going into the water, IDFG sampled the section of the Snake River that will be impacted - between the Twin Falls Dam and Centennial Park - to get information that will help rebuild fish populations in the future.
"We essentially came out here, electrofished, and sampled approximately 2,000 fish," Peterson said. "We put hole punches in their tail so that if we do see these fishes' mortality, we can get a ratio to marked and unmarked fish - and that's how we develop our population estimates."
During their sampling, IDFG found that the approximately six-mile stretch of the river has a mix of game fish and non-game fish.
"Some of the larger parts of the fish community include like largescale suckers, common carp and some small redside shiners," Peterson said. "In terms of game fish, we have sturgeon within the water, as well as smallmouth bass and some panfish."
Moving forward, IDFG will rebuild the impacted fish populations through translocations and stocking from fish hatcheries.
"Because we will have that baseline information, we'll be able to use that to identify translocations of fish - so we can go to another population, such as C.J. Strike Reservoir to collect smallmouth bass to bring in here and jumpstart that population back," Peterson said.
Natrix is a formulation labeled and approved by the EPA, and similar copper-based products have been used in Idaho for mussel, fish, algae and plant control. The treatment is not expected to impact any drinking water sources, the ISDA also said the Niagara Springs Fish Hatchery will not be affected.
The quagga mussel treatment will take place over 10 days, until Oct. 13. The copper-based formula is expected to break down in a 16-mile dissipation area as it moves downstream.
The Snake River treatment is part of the state's plan to eradicate the quagga mussels, which threaten Idaho's hydropower generation, irrigation and recreation. The invasive mussels could also disrupt the Snake River's food chain.
"Left unchecked, this could change a lot of these a lot of these fish population size structures, we could see changes in juvenile fish survival," Peterson said. "These muscles tend to compete for food sources that are are also utilized by some of these fish species."
IDFG said this in an evolving situation and biologists will continue to monitor the treatment area.
Quagga mussels veligers - the larval form of the mussels - were first detected in the mid-Snake River on Sept. 18. Since then, the ISDA has done extensive sampling on the river, finding veligers between the Twin Falls Dam and Centennial Waterfront Park. A plume with an adult quagga mussel was also found near Shoshone Falls.
The section of the Snake River from the Twin Falls Dam to Niagara Springs remains closed as agencies try to stop the "potential crisis."
More information about the quagga mussel treatment plan can be found on the Idaho State Department of Agriculture's website.
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