Biologists from the Iowa Department of Natural Resources (DNR) suspect that an 8-mile long fish kill on the West Branch of the Floyd River north of Maurice in Sioux County may have been caused by an unknown pollutant.
The fish had been dead for several days when DNR investigators reached the site on Sunday, August 14. The cause of the fish kill was not apparent during the initial investigation.
The following day, field tests showed ammonia levels within normal ranges and adequate dissolved oxygen in the river, indicating the pollutant had likely already washed downstream.
Early estimates indicate nearly 38,000 fish died in the event. Minnows, shiners, dace, chubs, and suckers were most affected, and an estimated 1,273 catfish also died.
DNR requested anyone with information related to the investigation to contact the Spencer field office at 712-262-4177.
source: Iowa Department of Natural Resources