What Killed 20,000 Shovelnose Sturgeon Earlier this Summer in Iowa?

It's not always runoff or human interference that can cause a catastrophic fish kill. Sometimes variables outside of our control can do massive amounts of damage. Take for instance the latest fish kill that occurred in Des Moines.

According to reports, the Iowa Department of Natural Resources (DNR) has been notified of a significant fish kill in the lower Des Moines River. An estimated 20,000 shovelnose sturgeon were found dead along a 60-mile stretch of the river, from Ottumwa to Farmington in southeast Iowa earlier this summer. DNR fisheries staff conducted an investigation, collecting water samples and testing dead fish to determine the cause of the kill.

Preliminary findings suggest that high water temperatures and low flows in the river were the main factors contributing to the fish kill. Water temperatures in the upper 80s exceeded levels known to be lethal for shovelnose sturgeon, which resulted in their mass mortality. Importantly, only shovelnose sturgeon were affected, with no impact on other species. Issues with high water temperatures during dry periods can also cause diminished oxygen levels.

The Des Moines River section below Ottumwa is known to have a significant population of shovelnose sturgeon, making this fish kill particularly significant. These long-lived fish play a vital role in the ecosystem, and it will take several years for their population to recover.

This is not the first time the Des Moines River has experienced fish kills caused by low water levels and high temperatures. The most recent incident occurred in 2012, prompting collaborative research between the DNR and the Missouri Conservation to better understand the impacts on shovelnose sturgeon populations.

Just in March, a fish kill of around 230 fish was due to a rapid change in water temperature. The shutdown of Xcel Energy's nuclear power plant in Monticello, MN was to fix a leak of mildly radioactive water that caused the fish kill in the Mississippi River.

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The DNR urges individuals to report any dead or stressed fish they encounter in lakes or rivers to their 24-hour spill line; that's 515-725-8694. Quick reporting allows the DNR staff to identify the cause of the fish kill and potentially intervene to prevent further harm. Links to the DNR Fish Kill site can be found here, with access to the current state fish kills available here.