CENTERVILLE, S.D. (AP)--The creeks that meander through the pastures and cornfields of eastern South Dakota don't look like much, especially when viewed in the usual way--from a highway bridge while traveling at 55 mph.

But a group of biologists and technicians are proving the streams are in fact teeming with life. And they are using the minnows, shiners and darters that live there to establish an early warning system for pollution.

The last week of July marked the beginning of the Vermillion Basin Watershed Assessment, a program mandated by the federal Clean Water Act to assess pollution on the Vermillion River and its tributaries.

As part of the kickoff, five researchers visited Frog Creek, a stream south of Centerville that is about as wide as a deluxe sofa. After dragging a seine 120 feet, they hauled out 75 pounds of fish.

"You walk around the banks, and you probably wouldn't have thought there were that many fish in here. Doing this, you get to see all these hidden things," technician Jeff Puthoff said.

As they hauled them out, though, the estimated 24,242 minnows could not have been more obvious.

"Holy cow," researcher Becky Banks said.

"Lotsa critters," said Jesse Willens, a University of South Dakota student.

As they dumped the wriggling deluge of silver scales into a wire-mesh box with a wooden frame, they realized how much counting and identifying they'd be doing.

"Oh, yeah. We'll be here all day," Deb Springman said.

She and Banks work for the East Dakota Water Development District in Brookings. The agency is near the end of a similar assessment on a stretch of the Big Sioux River from Brookings to Brandon. It soon will establish limits on pollutants such as sediment fecal coliform bacteria.

In addition to measuring such pollutants directly, scientists say that sampling "bioindicators" such as fish can provide important information.

"You can derive the condition of the river over the longer term by sampling something that has to live its life there," said Jay Gilbertson, director of the east Dakota district.

In the Vermillion River basin, which runs 150 miles from near Lake Preston to Vermillion, the community of fish species differ, but the idea is the same. At Frog Creek, Vermillion Basin project leader Steve Freeling said that community was sending positive signals.

"If you're getting this many fish, there's got to be something that's good in this stream," he said.

Most of the fish were about an inch long, and the vast majority were plains minnows, with a few fathead minnows, red shiners and others thrown in--11 species in all.

The abundance of plains minnows might be because of the sand and gravel in the stream bed of Frog Creek. The day before, the researchers had been at Camp Creek near Chancellor. That muddy stream bed is a perfect home for bullheads, and the researchers bore cuts on their hands from that species' spiny pectoral fins.

Puthoff said he used to love catching and eating bullheads as a kid, but "my tastes weren't that developed."

There are other examples of how the fish community responds to habitat.

A species called the central stoneroller, for example, needs a stream bed free of mud so it can dig for algae. White suckers eat algae, too, but they can get it by filtering mud, Freeling said.

Pollution also can alter the fish community. But although cattle stood in the creek nearby while the fish were being counted, it is hard to tell whether Frog Creek suffers from manure pollution.

That will have to wait until the Vermillion Basin study finishes in about three years. That will allow these researchers to trace the types and sources of pollution and point out ways to correct it.

"We'll know what areas need to be improved," Puthoff said. "If it's coming from farmland, they might be able to get some money to help restore their areas."

Date: 8/25/05