Montana Fish, Wildlife and Parks is asking for public comments on proposed state efforts to protect native westslope cutthroat trout in the Flathead Basin’s tributaries.

One half of Montana’s state fish, westslope cutthroat trout are native and unique to the Flathead Basin — unlike rainbow trout, which now also call the area home — and they have evolved for thousands of years to adapt to the landscape.

Hybridization between native cutthroats and non-native species like rainbow trout in the valley poses the risk of a major loss of biodiversity and “seriously threatens native cutthroat trout,” officials wrote in a press release issued earlier this month.

A study published in October — titled “High dispersal rates in hybrids drive expansion of maladaptive hybridization” — found that the increase in invasive crossbreeding and the spread of hybrid trout presents an overall threat to all subspecies of cutthroat trout, specifically regarding the genetic complexes that are unique to the westslope.

According to the study, which the wildlife agency cites in its proposed environmental assessment, non-native invasive genes boast a higher rate of dispersal in trout. Simply put, rainbow trout and hybrids spread across more space in less time than native cutthroats. The process is known as spatial sorting.

The study’s message is “pretty clear,” Sam Bourret, the study’s lead author and a state biologist, told the Inter Lake last year. “Hybrids are straying more throughout the system.”

Cutthroats are classified as a species of special concern by the state wildlife agency and the American Fisheries Society while the U.S. Forest Service and Bureau of Land Management deem it a sensitive species. According to Bourret, the greatest threat to the perpetuity of cutthroats is hybridization with invasive rainbow trout.

“By removing that threat, it’s one of the best ways to conserve cutthroat trout in the Flathead,” Bourret said of the state’s proposal this week.

Montana Fish, Wildlife and Parks is proposing to continue past efforts of removing and relocating hybrid fish and rainbow trout from the mouths and channels of Abbot, Sekokini, Rabe, Ivy and Third creeks to Pine Grove Pond in Kalispell. Department officials argue that this reduces threats to westslope cutthroat trout persistence while maintaining fishing opportunities for anglers.

Focusing on these specific areas will benefit native westslope cutthroat trout in tributaries in the Middle and North forks of the Flathead River, near Coram in Flathead County, according to the state agency.

“From a scientific standpoint, suppression of non-native fish can work and has worked in the Flathead in the past,” said Clint Muhlfeld, a research aquatic ecologist at the U.S. Geological Survey Northern Rocky Mountain Science Center.

According to Muhlfeld, the Flathead has some of the oldest, longest and most comprehensive genetic data sets regarding cutthroat trout.

A major threat to cutthroat trout, Mulhfield said, is the possibility of losing the genes or gene complexes that are adaptations to living in the Flathead Basin. When cutthroat trout lose those genetic complexes, they are less fit to survive.

Muhlfeld added that the state wildlife agency’s proposal is one of many efforts to reverse the spread of rainbow trout and protect the genetics of cutthroats.

ACCORDING TO officials with Montana Fish, Wildlife and Parks, genetically unaltered westslope cutthroats currently exist in less than 10% of their historic range in the United States and less than 20% of their historic range in Canada.

The proposed project would build upon efforts that began in 2013, though the state first began studying the issue in the early 2000s. The latest iteration of efforts would extend previous work and monitor the project by tracking the rate that hybridization continues to spread, the population’s genetic structure in streams targeted for suppression, and the relative number of hybrid and rainbow trout at capture sites.

According to the agency’s recent assessment, the South Fork of the Flathead River drainage, upstream from the Hungry Horse Dam, makes up about half of the remaining habitat for genetically pure westslope cutthroat trout. The North and Middle Forks represent a substantial portion of the remaining population in the state as well.

The environmental assessment looks at similar and past efforts to best protect the cutthroat trout in the Flathead, according to Dillon Tabish, Region 1 information and education program manager for the state wildlife agency.

By focusing on the mainstream, Middle Fork and North Fork of the Flathead River — along with certain tributaries — agency officials hope to remove non-native rainbow trout and cutthroat-rainbow trout.

The state agency plans to utilize trapping and electrofishing methods to catch the invasive fish during their spawning season in April and May. The proposal requires permits from the National Park Service and the U.S. Forest Service owing to the involvement of traps and jet boats.

Trapped fish will be transported to Pine Grove Pond, which is removed from the river system. According to Amber Steed, the lead on the project and a state fisheries biologist, similar past efforts have had a positive effect without overly affecting rainbow trout catch rates from anglers.

“I think that the Flathead is a really special place,” Bourret said. “Cutthroats are worth conserving.”

The public is welcome to comment on the plan before Feb. 17. Interested persons should send comments and questions to Amber Steed, Montana Fish, Wildlife and Parks, 490 N. Meridian Road, Kalispell, MT, 59901 or via email to asteed@mt.gov.

More information on the proposed project is described in the draft environmental assessment, which is available online at https://fwp.mt.gov/news/public-notices or at any FWP office.

Reporter Kate Heston can be reached at kheston@dailyinterlake.com or at 758-4459.