Deaths of 2,500 fish in Minnesota trout stream unexplained
State agencies are investigating what killed-off thousands of fish on a popular trout stream in southeastern Minnesota last week.
The fish kill on Rush Creek near Lewiston is similar to other events reported in the region in the past decade, sparking concern from trout anglers about whether or not state regulations are doing enough to protect Minnesota's freshwater.
The Minnesota Pollution Control Agency, the Department of Agriculture and the Department of Natural Resources have been investigating the incident since last Tuesday, but have yet to provide a further update on the investigation.
Initial information provided by the MPCA stated some 2,500 fish — mostly brown trout — died in the Rush Creek fish kill and there's reason to believe the deaths didn't occur naturally.
The agencies collected fish and water samples to explore all possible causes, including an "extreme weather event," according to the MPCA.
John Lenczewski, executive director of Minnesota Trout Unlimited, said the region's steep slopes and cold springs make Rush Creek a prized trout stream, but the local topography also increases the water's vulnerability to environmental contaminants.
A 27" brown trout washed up in apparent fish kill on Rush Creek near Lewiston, Minn. in late July. Photo courtesy of Robert Meyer / Minnesota Trout Unlimited.
"This isn't an isolated incident," he said. "Unfortunately, it's sort of a pattern."
While fish kills can occur naturally due to diseases or low oxygen levels, fish kills occurring after rainfall are often indicative of manure, pesticide or fertilizer runoff.
Toxic spills or discharges of wastewater or stormwater have also been linked to fish kills.
According to the MPCA, fish kills driven by rain events often have less-discernible causes.
For Lenczewski, the possibility that state agencies won't be able to pinpoint the cause of the Rush Creek fish kill is concerning — especially because the preceding rainfall event was a relatively common one, he said.
"If the rules are inadequate, they should be changed," he said, adding Minnesota Trout Unlimited will be pressing for reexamination of the rules and land practices that he believes might be cutting the margins too close.
"We all want clean water," Lenczewski continued. "So this should be a concern to everyone, not just trout anglers."
