They report that their investigators were unable to find the cause of an 8-mile long fish kill on the West Branch of the Floyd River north of Maurice in Sioux County. The fish had been dead for several days when DNR reached the site Sunday. Field tests on Monday showed ammonia levels within normal ranges and adequate dissolved oxygen in the river, indicating the pollutant had likely already washed downstream.
DNR officials say early estimates indicate nearly 38,000 fish died worth approximately $10,000. Minnows, shiners, dace, chubs and suckers were most affected, and an estimated 1,273 catfish also died.
A second fish kill on the Rock River in north Sioux County was located in a pool off 10th Street on the west side of Rock Valley. DNR staff say they found about 24 decaying carp in very stagnant water. They speculate that the carp were trapped as water levels receded after rains last week. Water samples have been sent to a laboratory for testing to see if the fish kill was related to petroleum products or to oxygen sags in the pool.
The DNR says they’ll continue to look for a responsible party for the fish kill on the West Branch of the Floyd. If anyone has information that would aid in the investigation, they are asked to please contact the Spencer field office at 712-262-4177.