A 42-mile section of the Des Moines River in southeast Iowa was home to one of the longest fish kills in the state’s history recently, with nearly 58,000 dead fish counted with a value estimated by the Iowa Department of Natural Resources at more than $10.1 million.
Dead fish were found in the river from the dam at Eldon to the Farmington bridge on Highway 2 beginning July 7.
The majority of fish killed, 37,159, were shovelnose sturgeon. The DNR estimated the sturgeon alone are worth more than $9.86 million, based on an estimated value of $116.20 per pound and the dead fish averaging about 2 pounds.
The DNR estimate is based on figures from the American Fisheries Society for monetary value in fish kills.
The high cost per pound is attributed to the demand for shovelnose sturgeon eggs that are highly sought as caviar. They are the only fish in North America harvested for their eggs and have become more sought after since Caspian Sea and Black Sea sturgeon have become endangered.
“They’re so high-priced because of the potential economic loss,” said Gil Larschied, chief of the fisheries bureau of the DNR.
DNR spokesman Kevin Baskins said the high value of the kill seems extreme, but the DNR attaches dollar values to all fish kills based on the American Fisheries Society formula in the event it’s determined to be caused by a spill and the agency seeks payment of damages.
Larschied said shovelnose sturgeon are especially susceptible to high water temperatures.
DNR fisheries biologist Mark Flammang, who investigated the kill, said water temperature was to blame.
“You just don’t see rivers at 97 degrees, and it was 97 degrees at every site that we sampled,” Flammang said. “I’ve never seen water at that temperature in Iowa.”
The effect of high water temperature on fish likely was compounded by stream flows that had fallen from 5,000 cubic feet per second before July 4 to 1,200 CFS on July 7, the DNR said in a news release.
In addition to shovelnose sturgeon, Flammang found more than 12,000 channel catfish, nearly 1,900 walleye, more than 1,100 flathead catfish, 1,500 freshwater drum, 750 carpsuckers, 370 white bass, 45 shorthead redhorse and 25 goldeye.“It looks like a lot of fish, but I don’t expect this fish kill to have a noticeable impact on the fish population in this stretch of the river,” Flammang said.