Idaho’s Response
Through ISDA’s Early Detection Monitoring Program, quagga mussels were confirmed in the Twin Falls area of the Snake River on September 18th. The discovery of quagga mussels in the Snake River marked the first time a rapid response plan had been put into action for quagga mussels in Idaho.
The response to the quagga mussel detection in the Snake River is a major priority to the ISDA, Governor Little’s Office, as well as several federal, state and local agencies. The quagga mussel response is an ongoing effort for State of Idaho to protect our waters and way of life from a potentially devastating infestation.
Since the detection in 2023, ISDA has doubled quagga mussel sampling, ran more inspections stations, increased statewide communications, added manpower, and collaborated with more partners. The ISDA Invasive Species Program has more information and resources than ever before to combat this invasive species.
September 2024 Detection
The 2024 monitoring results showed a decrease of quagga mussel presence in the affected stretch of river since the pre-treatment surveys in 2023. Positive detection locations in September 2024 included in the Shoshone Falls pool, Pillar Falls and the Twin Falls Reservoir behind Twin Falls hydroelectric facility. Quagga mussel reproduction is more active in warmer water temperatures, making late summer the most likely time to detect the mussels in the Snake River.
In response to the 2024 detection, ISDA is implemented a copper treatment in the Mid-Snake River. The treatment took place October 8-20 and utilized the same chelated copper product as the 2023 treatment, Natrix.
In addition to the application of the chelated copper (Natrix), ISDA implemented a potash (potassium chloride) treatment in still water ponds on the Mid-Snake River in February and March. The second treatment reflects the aggressive approach to maximize efforts in the complex river system with the ultimate goal of complete eradication of this species.
Read the most recent news release HERE.
2023 control strategy
Since the discovery of quagga mussel larvae in the Snake River, ISDA has been dedicated to an aggressive approach for treatment to protect Idaho’s waters from these mussels.
ISDA implemented a treatment of the river with a chelated copper product. It was the first treatment of this type and scale ever attempted in North America. Sampling results indicate the chelated copper treatment was effective in reducing the mussel population.
ISDA utilized a comprehensive treatment strategy, which was developed with the review and assistance of many agencies and groups including; Governor Little’s Office, Idaho Department of Fish and Game, Idaho Office of Species Conservation, Idaho Department of Environmental Quality, Idaho Department of Water Resources, Idaho Department of Parks and Recreation, Idaho Department of Lands, Idaho Power, canal companies, Idaho Water Users Association, U.S. Environmental Protection Agency, U.S. Fish and Wildlife Service, U.S. Geological Survey, U.S. Army Corps of Engineers, U.S. Bureau of Land Management, and U.S. Bureau of Reclamation.
We appreciate the continued assistance and cooperation of the Twin Falls and Jerome County Commissioners, the City of Twin Falls, and the Idaho Office of Emergency Management.
Containment measures
Throughout the 2023 and 2024 treatments, ISDA closed public access to the affected stretch of Mid Snake River. The closures were in place to minimize the potential spread of quagga mussels as well as prioritize the public’s safety.
Today, the Snake River is open with a mandatory decontamination in place from Broken Bridge (Yingst Grade) and Hansen Bridge. Any watercraft or conveyance is required to be inspected prior to launch and decontaminated upon exit of the river. The inspection and decontamination station is operating at Centennial Waterfront Park or Twin Falls Reservoir.
2023 and 2024 delimiting surveys
To better understand the extent of the physical range of impacted area, ISDA staff survey the water in the Mid-Snake River area for quagga mussel larvae. ISDA staff and partners surveyed at a rapid pace to map out any other presence of quagga mussel larvae or adults in the area.
Samples from the Snake River are sent to a lab to identify any mussel larvae in the samples through microscopy. Any samples identified as possible quagga mussel are then transferred to another lab for PCR (genetic) confirmation.
In 2023, ISDA divers identified an adult mussel that was located near Shoshone Falls, which was consistent with the veliger sample data. Sample results indicated there was a population of quagga mussel larvae specifically in the Shoshone Falls area. No larvae were confirmed upriver of the Twin Falls Dam or downriver of Centennial Park. Sampling occurred in surrounding lakes and reservoirs, upstream from Milner Dam to American Falls, and downstream to the Idaho Power Dam Complex at Hagerman.
In 2024, positive detection locations include in the Shoshone Falls pool, Pillar Falls and the Twin Falls Reservoir behind Twin Falls hydroelectric facility.
Both in 2023 and 2024, survey data was used in ISDA’s treatment planning.
Treatment Notifications
The ISDA along with several partners worked to inform residents of the Magic Valley and all Idahoans of the quagga mussel response efforts. Communication to the public is a crucial aspect of the rapid response plan. The following communication methods were employed.