News and Activities

Contaminants Biologists Respond to a Large Fish Kill in Illinois

Date Posted: June 29, 2009

On June 21st, 2009, thousands of fish died suddenly in the Rock River, IL. The Rock River starts in Wisconsin and flows through the northern part of Illinois before draining into the Mississippi River. Some of the fish species killed included trophy sized flathead catfish and shovelnose sturgeon. The Rock River is an important sport fishery for Illinois and is used for all sorts of water recreational activities.

Biologists were concerned that the cause of the fish kill could also directly harm the mussels and birds that use the Rock River. Plus the fish serve as hosts for the development of immature mussels. Resource specialists from the U.S. Fish and Wildlife Service have spent the last several years propagating federally listed endangered Higginseye pearly mussels in hatcheries. The juvenile mussels from the hatcheries were reintroduced into mussel beds along the lower reach of the Rock River as project to help recover this imperiled species. The Rock River also supports many different species of migratory birds that are dependent on the river and associated wetlands for food and nesting habitat.

Environmental Contaminants Program biologists and biologists from other programs at the Ecological Services Field Office located in Rock Island, IL immediately collected river water for testing. In addition, these biologists supported State agencies that were responding to the fish kill. The cause of the fish kill is unknown at this time. There was a record rainstorm that caused flood conditions in the Rock River. There was also train wreck upstream of the fish kill that spilled gasoline ready ethanol into the Rock River. Ethanol is toxic at high concentration and can oxidize to acetaldehyde which is toxic at lower concentrations. The breakdown of ethanol in surface water consumes dissolved oxygen from the water column which can stress or kill fish and mussels. Environmental Contaminants Program biologists provided technical assistance to the railroad company, U.S. Environmental Protection Agency, and the Illinois Environmental Protection Agency for the emergency response related to the train wreck. The technical assistance included review of sampling plans and methods for testing the water for ethanol and other potential causes for the fish kill. Contaminants biologists are supporting State agencies to help determine the cause of the fish kill and will continue to monitor bird life and the health of the endangered mussel beds. The Natural Resource Trustees including the U.S. Fish and Wildlife Service may initiate a natural resource damage assessment if the cause of the impacts to the river is related to an unpermited release of hazardous substances. The goal of the damage assessment is to restore injured natural resources and to compensate the public for the lost use of natural resources.

Michael Coffey (309)757-5800 x206 and Aleshia Kenney (309)757-5800 x218

U.S. Fish and Wildlife Service:

The Natural Resource Damage Assessment and Restoration Program

Midwest Region Natural Resource Damage Assessment Program

Mussels of the Upper Mississippi River System

Last updated: June 12, 2015