From there it runs into Pactola, and then out into the basin below, which is considered some of the best trout fishing in the Black Hills, and then heads toward the Plains, but for about 15 miles it courses through terrain plastered alternately with housing and rather remote, secluded areas. Some of this stretch has become compromised for trout fishing by diatoms, which mysteriously started growing in large quantities a few years ago.

Diatoms are normally found in cold glacial streams, but for some reason, they've really taken off here, damaging the trout stream by covering spawning areas and insect habitat. In the stream, the diatom areas look something like wet toilet paper.

Biologists are still studying this lifeform, which apparently is flourishing better here than anywhere else. This past year they have worsened in some areas and retreated in others.

On the edge of Rapid City, Rapid Creek flows past the Cleghorn Springs Fish Hatchery and then into Canyon Lake. From there downstream through Rapid City is some of the best trout fishing available, with trout numbers comparable to the finest smaller blue ribbon trout streams in the West. Lots of trout habitat has been put in there over the past two decades by the South Dakota Department of Game, Fish and Parks.

The stretch of this stream that Stephenson recommends most highly is the basin area below Pactola Dam. "The best area by far is the catch-and-release area below Pactola," he said. "With supplemental stockings and the wild fish, it is good."

Both brown trout and rainbow trout are in this stretch. You can see them finning below the water surface on about any day.

"They did decide to do a little bit of stocking because of the lower fish numbers," said Stephenson. "It still has a fair amount of wild fish. It has become a nice mix. They didn't saturate the fishery with too many hatchery rainbows. Some of the rainbows they put in are holding over nicely, and acting like the typical basin fish we see. They're getting fat and are feeding on scuds and midges. But there are still nice wild browns and rainbows in there, too. "

Both species are spawning here. And of course, brown trout successfully spawn in all of the streams in the Black Hills, except for the creeks, which harbor brook trout.

"The size (in Pactola Basin) averages 12 to 14 inches," said Stephenson. "And then there are a fair number of 15- to 17-inch-range fish, and a few that you come across in the 19- to 21-inch range. There are some bigger browns, but also some rainbows in that size range, too. That is all catch-and-release. It is the first two miles downstream from Pactola."