By Tim Krohn
CNHI
MANKATO — The Minnesota River contains less phosphorus, a whole lot more fish, less sediment and is seeing a rebound in the otter population.
But nitrate levels haven’t improved much, if at all, mussel populations are just holding steady, and the amount of prairie land continues to dwindle.
Those are some of the conclusions in a first-ever trends report recently completed by the Water Resources Center, Minnesota State University and the Minnesota Pollution Control Agency.
Scott Kudelka of the Water Resources Center said they pulled various data and research together to get a big picture of what’s happening in the 335-mile-long river.
“By far the best news is the fishing. That keeps coming back. The fishing has really gotten better. They’re seeing more species and higher numbers,” Kudelka said.
Several paddlefish and sturgeon were netted near New Ulm last spring and other species have also flourished, including catfish, which, contrary to perception, need relatively clean water to do well.
“The Minnesota is known for those big catfish. People are excited about them,” Kudelka said.
The lovable otter has been making a steady but slow return to the river basin. Otters across the state were wiped out in the early 1900s with the last otter seen in this area at Swan Lake in 1917. They were reintroduced in the upper Minnesota River in the 1980s.
Department of Natural Resources furbearer biologist John Erb said the otters are well established in the upper and lower portions of the river with those in the lower end coming up from the Mississippi River.
“They seem to be doing good, but there weren’t many in the middle area near Mankato. I’m a bit perplexed why they aren’t there,” Erb said.
He doesn’t think there are any pollution or habitat problems in the middle stretch, noting otters are abundant in much dirtier rivers.
“I don’t have any particular concern there’s anything wrong there, I think in time they’ll continue to fill in and do fine.”
He said he’s considered releasing otters in this area, “But I tend to think they do better if you just let them naturally fill in.”
Erb, based in Grand Rapids, hasn’t done a survey on the Minnesota for several years and hopes to do a new one soon.
Otters disappeared because of heavy trapping, massive landscape changes and pollution, Erb said.
“As bad as rivers are now, they were even worse then.”
Kudelka said the number of species of mussels has held at about two dozen since the early 1980s. That’s better than it was earlier in that century, but still about half what it was historically.
He said mussel populations are much higher in the upper stretches of the river basin.
“In the Chippewa watershed, you can stand anywhere and pick up 10 live mussels. Here in the Blue Earth, we find seven or eight in a mile and a half,” Kudelka said.
Phosphorus levels have dropped significantly, mostly because cities along the river have put in new sewage treatment plants.
Depending on the stretch of river, nitrates are trending up, down or holding. Nitrates come from fertilizer runoff and animal and human waste.
And the amount of prairie in the basin continues to decline, losing to crop land and development. The DNR estimates nearly 78 percent of the Minnesota River Prairie was actually prairie with 13 percent non-forest wetland in the 1890s. A century later, the same area was 0 percent prairieland, only 1.9 percent non-forest wetland, 9 percent grassland and 83 percent cropland.
The full report can be seen at: http://mrbdc.mnsu.edu/mnbasin/trends/index.html.
