St. Louis River Alliance

Fish Tumors and Deformities

In 1991-92, a number of fish sampled on Crawford Creek, a tributary to the St. Louis River, had spinal deformities and possibly tumors.  Harmful chemicals in river sediments have been shown to increase the incidence of tumors in fish such as suckers and bullheads. The rate of tumors found in these types of fish caught in the St. Louis River was found to exceed the rate of areas not impacted from contaminated sediments.

Addressing the Issue

Since 2005, two of the most contaminated sites on the St. Louis River have been cleaned up, reducing the amount of contaminated sediments that have been known to increase the incidence of tumors in fish.

It is a current priority to remove this issue from the river’s list of concerns. In spring 2011, federal, tribal and state agency employees collected white suckers from the St. Louis River to test for the presence of tumors and deformities. During 2011-2012, the Alliance is facilitating and coordinating the exchange of information between several state, tribal and federal agencies on the progress that has been made already on this issue. The Alliance will also conduct public meetings to provide information on the fish collection results, ask for feedback and help determine what steps to take next.

What You Can Do

If you are fishing on the river and and catch a fish with tumors or deformities, please contact the St. Louis River Alliance at (218) 733-9520, or email at