Fish and Game and the Idaho State Department of Agriculture actively monitor for fish mortalities during quagga mussel treatment in the Snake River

Idaho Fish and Game and Idaho State Department of Agriculture (ISDA) staff are monitoring the Snake River for fish mortalities as a result of the chelated copper treatment for quagga mussels. It was anticipated that there would be significant fish mortality in the six-mile segment of the river once treatment began. 

Staff are collecting biological data on fish collected. At this point, data has been collected on several hundred fish. The most abundant fish sampled have been largescale suckers, common carp, northern pike minnow and yellow perch.

Ten sturgeon have been found, ranging from six feet to under two feet. These sturgeon were hatchery-reared and stocked fish, as are most sturgeon in this stretch of the river. 

Fish and Game will continue to monitor the river for fish mortalities over the coming weeks, extending the monitoring past the end of the treatment period. 

Quagga mussel larvae was first detected in the Snake River near Twin Falls on September 18, 2023, by routine monitoring conducted by the ISDA.

The ISDA along with several other agencies identified chelated copper as the appropriate treatment to eliminate the mussels. The treatment of a six-mile section of the Snake River began on Tuesday, October 3, 2023.