When local groups stocked rainbow and brown trout into a stretch of creek at Spruce Hill County Park in Douglas County this past spring, they were eager to see how those fish would respond through the heat of the summer.
Trout are cold-water fish species. Rainbows even more than brown trout are susceptible to water temperatures that get much higher than 70 degrees.
A group of nine area organizations led by the Viking Sportsmen in Alexandria privately funded the stocking of about 350 rainbows, which were all females, on April 9 and then almost 3,000 brown trout on June 15. Since May, the Glenwood Area DNR has used automated temperature monitors to track how warm areas of the creek got through the summer.
“We’ll monitor it through August, but we did have some water temperatures bump into the 80s during July,” Glenwood Area Fisheries Manager Dean Beck said on Aug. 15.
That left Beck still questioning how well trout will ultimately survive long term in this stretch of stream. He noted the absence of many sustained days where air temperatures reached the 90s this year and whether or not a hotter summer could hurt the trout’s chances.
There was good news for those who want to see trout be an option for area anglers to target. Along with temperature monitoring, the DNR also walked a portion of the creek in the late summer and used electrofishing techniques to track numbers. Electrofishing is the process of employing a weak electric current to attract and temporarily immobilize a fish for easy capture.
“They still got good numbers of brown trout,” Beck said. “They didn’t find any rainbows. They didn’t do the whole mile of creek, but the stretches they did check they didn’t find any rainbows.”
Brown trout are considered the hardiest of the trout species and are known to tolerate water that is warmer and less clear than a rainbow or brook trout.
The fact that the DNR sampled water that reached 80 degrees in spots does not mean the whole stretch of creek reached those temperatures. Mike McDaniel, one of the co-chairs with Alexandria’s Bob Gibson on the trout-stocking project, tracks both water temperature and water quality data on the creek for the Minnesota Pollution Control Agency.
“I’ve got water temperatures in the low 70s, but that’s as high as I’ve got,” McDaniel said. “I’m sure there’s spots there that are shallower that have higher temperatures. I do my reading under one of the bridges. I’m required to do my reading at the same place every week.”
The rainbow trout that were released at a much lower density were bigger in size than the brown trout that averaged around six inches in length. Those rainbows were more ready to immediately catch and eat if anglers chose to do that.
McDaniel is at Spruce Hill County Park to get water samples each week and has brought his fishing pole along almost every time.
“When I’m there, I’ll probably fish for about an hour,” he said. “Maybe two times out of all the times I’ve been out there this summer I haven’t caught a fish. I’ve caught mostly rainbows. Earlier, I’d catch two or three. Now, I’ll usually catch one. I caught one as recent as (early August), so there’s got to be some in there. It was a small one, but it survived so it must have found a cool spot or a deep hole. I’m optimistic there’s still some fish out there.”
Fish species in lakes, rivers or streams are adept at finding the water temperatures that fit their needs if they are available. Trout will gather in deeper holes that produce those cooler temperatures. McDaniel walked a nearly three-quarter mile stretch of the creek in mid-August and feels there are plenty of those holes available for the fish.
“I had my chest waders on and there were a couple spots I had to back up,” he said. “That’s got to be about four feet, I would guess. I would say 36-40 inches would be the average pools that are in there and there’s got to be a dozen of them in that three-quarter stretch I walked. Then there’s a lot of undercut banks and those are areas trout like to get under for that shade.”
McDaniel fishes some of the streams in southeastern Minnesota, an area of the state that is much more noted for its trout opportunities. He said the water quality in the stretch of creek at Spruce Hill Park is better than what he sees in the southeast.
“The water qualify up here I think will help us too,” McDaniel said. “I’ve been able to read the entire tube every single time I’ve been out there even after heavy rains. If you look on a map, Spruce Creek really doesn’t have a whole lot of agricultural land right up to it.”
Gibson and McDaniel have both been relatively encouraged by what they have seen so far, especially as it pertains to the survival of the brown trout. Those fish are still small, but McDaniel says the fish have good potential to grow with plenty of minnows throughout the creek. Now they are eagerly waiting to see how the trout respond through the winter.
“Bob and I call this the experiment because nobody really knows what’s going to happen,” McDaniel said. “We’re hoping they find those pools and survive the winter and continue to grow. (The brown trout) won’t spawn for a couple years yet, but that’s the ultimate goal is to get them to spawn and get some natural reproduction.”