North Platte fishery showing resilience after Mullen Fire

LARAMIE — A year after last fall’s Mullen Fire, fisheries within the burn area appear healthy, Wyoming Game and Fish Department biologists report. 

Fisheries biologist Chance Kirkeeng said survey sites this summer included the North Platte River at Pickaroon as well as Muddy Creek, Lake Creek and various points along Douglas Creek. Population estimates at each site showed that there hadn’t been any large die-offs since the fire. 

Biologists found all the species they expected to find in the places they expected to find them. They also found trout in a variety of sizes, indicating individuals are growing and reproducing. 

“We’re happy with what we saw this year,” Kirkeeng said. “It’s great that the fish are still there.” 

Bobby Compton, the Laramie Region fisheries supervisor, said fisheries were in good condition. 

“If we compare them to pre-fire surveys, there probably would not be a noticeable difference,” he said. 

The Mullen Fire started Sept. 17, 2020, and burned more than 176,000 acres over five weeks until a winter storm finally brought a foot of snow to the Snowy Range. 

The worst-case scenario for a fishery following a wildfire is a widespread fish die-off caused by ash running into a stream or river, suffocating the fish. Waters running below steep slopes in intense burn areas are the most vulnerable to such events because a large amount of ash could run directly into the water following a heavy rain. 

“The ash suffocates the fish,” Compton said. “It gets in the water and they can’t take up the oxygen in their gills.”

Anglers reported seeing fewer fish in Douglas Creek this summer than they had in the past, prompting biologists to make sure they included it in their surveys. They’ll want to hear reports from other areas as well, Kirkeeng said. He reported that the water in the North Platte was off-color and darker than normal, but fish appeared healthy and plump overall. 

“We use plumpness as an indicator of health,” he said. 

They looked at Lake Creek and Muddy Creek because of the burn severity in those areas. The day before their survey, a heavy summer rain turned Lake Creek black with ash, but by the time they did their sampling the water had cleared. 

“It didn’t seem like there were any large impacts,” he said. “It was really cool to see how (the ash) flushed into the system and how quickly it cleared up, and the fish were still doing good.” 

As the habitat regenerates in the years following the fire, grasses, forbs and shrubs in riparian areas will continue to add further protection against ash entering the watershed. 

Areas that endured the hottest burns will remain vulnerable for several years, however. Meanwhile, nutrients released by the fire will benefit the entire habitat, increasing food supplies such as insects. 

“If we can get through these big rain events — those are the biggest, scariest things,” Kirkeeng said. “If we can get through those without some major parts of the stream dying off, we’ll be in good shape.” 

The North Platte system has benefitted in recent years from multiple projects that have improved fish passage and fish habitat in the river and its tributaries. Government agencies, conservation groups and landowners have collaborated to remove barriers such as dams and irrigation diversions, reconnecting more than 100 miles of fish habitat. 

In 2018, the Encampment River and the North Platte River were reconnected for the first time in more than 90 years. Kirkeeng said those projects have made the wild trout fishery more robust and resilient. 

“It’s a really good system,” he said.