LEAD, S.D. (AP) — A study that focuses on ways to cool South Dakota’s streams during the hottest times of the year in an effort to preserve the trout population is yielding positive results, officials from the South Dakota Game, Fish and Parks say.
Jeremy Kientz, a fisheries biologist with the agency has been working to discover ways to cool the waters, in a study that specifically focuses on French Creek in Custer State Park. French Creek, he said, is one of a few trout streams in the Black Hills that can reach temperatures up to 80 degrees for several hours a day, increasing the chances of trout mortality.
“We’ve had a couple instances here in the Black Hills where we’ve had trout fish kills because of temperatures that are too high in the summertime,” Kientz said. “When the water temperature hits 80 degrees and it stays there for a little while, the trout will die. Even at 75 degrees, trout shut down and they don’t eat. So now, you not only have a survival issue, but a growth issue.”
But working on ways to cool the streams is not easy, Kientz said. Building shade takes time, and dams have become socially and culturally unpopular, not to mention expensive. So, Kientz said he has been working with mechanical engineers from North Dakota State University to build small pockets of cooled water, where trout can seek refuge when temperatures rise, the Black Hills Pioneer reported.
“Essentially the prototype that we’re using is a water tank and the water is getting pumped out of that water tank into a chilling unit. Then it goes through the chilling unit down to a box in the stream,” Kientz said. “The fish can swim in and out of the box in the stream where the cooler water is. We’re not actually cooling the stream itself, but small pockets contained within these boxes that are supposed to act as a refuge. So, when the water temps get high fish will sense where colder water is and move to it.”
The boxes, he said, can cool the water to as much as 5 degrees less than the rest of the stream, which can be beneficial during those hot periods in such streams as French Creek and Spring Creek, where temperatures can get up to 75 or 80 degrees.
Though Kientz said the Black Hills has not suffered major trout losses due to stream temperatures, the French Creek study will help biologists to become proactive if the current drought continues. During times of drought when water levels decrease, fish have less opportunities to find deep water with lower temperatures, and mortality rates could increase. Additionally, he said the science could preserve populations in Arizona and New Mexico, where biologists are seeing threatened trout species.
“We’re probably not in dire straits yet,” he said. “If our streams are only hitting 80 degrees for a couple of hours typically the fish aren’t going to die off. If the trends continue and we see these rising stream temperatures over the years, then 10 years from now this may be something we are glad that we did and we may actually start to implement it on a permanent basis at that point.
“In Arizona and New Mexico, trout species are threatened to the point of losing populations,” Kientz continued. "If you look at it from a cultural standpoint for Native Americans or just the general population, losing a species would be much more detrimental than us losing a few trout in French Creek. Something where there is a little more dire situation would be where this would be implemented at this point. We’re trying to look down the road and say ’we see something concerning, let’s get started on it now before things get to a place where we need it. We’re trying to take a proactive approach before we need to be reactive.”