For months, Bill Prater watched Horseshoe Lake slowly disappear.
From his home a few hundred yards away, the past president of the Loveland Fishing Club saw the privately owned reservoir shrink into a patchwork of isolated pools as places that had held water earlier in the summer gradually became mud flats.
Read more 5 overlanding destinations in Colorado for those seeking the road less traveled
So he wasn’t exactly surprised when the lake’s fish began dying and floating through the inlet to Boyd Lake last weekend.
“The lake is essentially emptied,” he said. “And that’s when the die-off really took hold.”
What followed was dramatic, but not entirely unexpected in a summer marked by prolonged heat and dwindling water supplies.
Colorado Parks and Wildlife officials estimate that thousands of fish died in Horseshoe before entering the Boyd Lake channel, creating a startling — and increasingly unpleasant — scene that quickly spread across social media. Most of the dead fish were common carp, with smaller numbers of walleye, white bass, shad and catfish.
Because Horseshoe Lake is privately owned, CPW does not manage or stock its fishery and did not investigate the conditions that caused the die-off. The Greeley-Loveland Irrigation Company manages water levels within the irrigation system that connects Horseshoe and Boyd lakes. The ditch company could not immediately be reached for comment.
AJ Macdonald, president of the Horseshoe Lake homeowners association board, provided an email that he said was sent to residents within the HOA. The email said the board reached out for help in saving the fish population after learning that the irrigation company “intended to draw the lake to such a low level.”
After contacting the ditch company and Colorado Parks and Wildlife, and learning “saving our fish was not a high priority,” the board reached out to the fish farm that stocked Horseshoe Lake and came up with a plan to save the fish by relocating them and then restocking them the following year, according to the email. They applied for a permit from the state to do so legally.
“The owner of the fish farm was assured by the state that our permit would be approved last week and that they could start moving fish immediately,” according to the email. “No action has been taken as our permit has still not been issued. Unfortunately, now all our fish have died. “
CPW crews were able to salvage some fish that were still alive in the inlet and relocate them to another body of water that already contained carp. The remaining carcasses will largely be left in place.
The agency also emphasized that the fish did not die in Boyd Lake and that the lake’s existing fishery has not been affected.
“There’s just dead fish that flowed into the inlet,” CPW Public Information Officer Kara Van Hoose said. “There’s not a lot you can really do.”
Although the exact cause of the Horseshoe Lake fish kill has not been determined, experts say prolonged heat and shrinking water supplies have created conditions that make fish kills more likely across Colorado.
“The hotter the water is, the less oxygen it naturally holds, and, at the same time, the hotter the water is, the more oxygen fish use,” said Chris Myrick, a Colorado State University professor of fisheries and aquatic sciences. “So it’s a double whammy.”
Read more State of New Mexico sues Justice Department and Todd Blanche, saying they blocked its Epstein probe
When a lake shrinks, fish can also become concentrated into a smaller volume of water, further increasing demand on a limited oxygen supply.
“You have a limited amount of water, limited amount of oxygen, fish that are using a lot of oxygen even when they’re resting,” Myrick said. “Then you just run out of oxygen.”
Myrick did not inspect Horseshoe Lake and cautioned that confirming the cause of a fish kill normally requires water-temperature and dissolved-oxygen measurements taken at the site. Investigators may also test for chemicals, toxic algae or other possible causes.
Still, he said the frequency of fish kills and emergency fish salvages around Colorado this summer is not surprising.
“I think this year it’s been exacerbated by starting off with relatively low water levels in some of the reservoirs,” he said. “And then high temperatures just make it worse.”
The dead fish themselves are unlikely to pose a danger to Boyd Lake’s surviving fish or to wildlife, Myrick said. Unless a toxic substance caused the deaths, carcasses are commonly left in place, where scavengers consume them or they decompose and return nutrients to the ecosystem.
That natural process has not made the inlet a pleasant place to visit, according to Prater.
Dead fish have collected in the shallow water and along the exposed lakebed, where some remaining fish could still be seen swimming among the carcasses earlier this week. As decomposition set in, the piles produced an increasingly foul smell, Prater said.
They have also attracted an array of hungry birds, like herons and gulls, taking advantage of the abundant food.
“If you’re a birder, you’ll be able to see all kinds of them,” he said.
Prater also said he has noticed signs of stress among fish in local fishing spots and worries that additional lakes could become vulnerable if temperatures climb again.
“This might not be the end of it,” he said.
Get more Colorado news by signing up for our daily Your Morning Dozen email newsletter.
Read more Bear hanging around north Louisville neighborhood captured and released in wild
