Arctic Grayling (Thymallus arcticus)

Principal biologist(s)

Carter Kruse, Eric Leinonen

Project Locations

Green Hollow Reservoir II, Cherry Creek & Spanish Creek, Flying D Ranch, MT
Willow Creek, Snowcrest Ranch, MT

Project Partners

US Fish & Wildlife Service
Montana Department of Fish, Wildlife & Parks

Conservation Problem

Arctic grayling are widespread throughout drainages of the Arctic and northern Pacific Ocean, but distinct populations in Michigan (now extinct) and southwestern Montana have experienced significant declines due to competition from non-native trout and habitat alterations. Fluvial arctic grayling in Montana were once widespread in the Missouri River basin above Great Falls. Over the past 100 years, populations have declined in range and abundance and now occupy about 4% of historical range in Montana.

Conservation Status

  • Considered a Species of Greatest Conservation Need by Montana Fish, Wildlife & Parks
  • The USFWS ruled in 2010 that the Upper Missouri River Distinct Population Segment (DPS) of Arctic grayling was warranted for listing under the ESA but precluded by higher priorities. By 2014 the USFWS determined that conservation efforts by federal, state, and private organizations had improved the species status to a point where listing was no longer warranted.

Project Recognition

2014 MTFWP and USFWS – Arctic Grayling Conservation Award

Project Goals

Our overall goal is to maintain a conservation brood stock of Big Hole fluvial Arctic grayling in Green Hollow Reservoir II to support range-wide restoration and restore self-sustaining populations of Arctic grayling on Turner Ranches and surrounding landscapes to improve their conservation status.


We aim to manage fluvial Arctic grayling in Green Hollow II in a manner that promotes a healthy grayling brood stock and supports restoration efforts in southwestern Montana. The brood fish will be disease free, average 10 inches in length, and provide at least 250 adult females for spawining and 300,000 eggs for restoration each year. Arctic grayling restoration on Turner Ranches will be implemented in at least two sites; exhibit densities of 20 adult fish (i.e., >100 mm total length) per km; and demonstrate successful recruitment (i.e., young of year or multiple age/size classes present) at least once every three years.

Project Background

TEI has been a partner in grayling conservation in Montana since 1998 when Big Hole fluvial Arctic grayling were stocked into Green Hollow Reservoir II to establish a brood stock. The brood stock was intended to serve as a genetic reservoir for Big Hole grayling and a source of grayling eggs for restoration projects across southwestern Montana. Over the past 20 years, TBD has provided invaluable assistance towards grayling restoration by managing the reservoir and brood stock population for these purposes. In 2002, a fish barrier was constructed on Green Hollow Creek to prevent grayling from moving into and spawning in the creek channel. Since 2003, TBD has worked to remove non-native trout from the reservoir and inflowing creek. Each spring TBD staff assist MTFWP with disease sampling and spawning of grayling. Over the past four years (2015-2018), Green Hollow II grayling have provided approximately 750,000 viable eggs for research on reintroduction of grayling in Michigan; restoration projects throughout southwest Montana; and large-scale restoration in Yellowstone National Park.

Unusually high spring runoff in 2011 deposited large amounts of gravel in the Green Hollow Reservoir II inlet and, despite efforts to disrupt spawning, grayling naturally reproduced below the fish barrier in 2012-15. Beginning in 2016 a bypass system has been installed annually for about 4 weeks in the spring to prevent spawning in the creek inlet. The wild born progeny from 2012-15 overpopulated the brood pond and resulted in smaller average adult sizes. In 2015 a decision was made to transfer more than 500 of the wild born grayling to lower Green Hollow Creek (below Green Hollow Reservoir I). An additional 536 juvenile grayling were captured and moved during spring trapping activity in 2016. These fish have unrestricted movement into the NF Spanish Creek and, ultimately, the Gallatin River, thus representing the first stocking of fluvial Arctic grayling into the Gallatin River system since their local extinction. Additionally, grayling have escaped from Green Hollow II and established a self-sustaining population in Green Hollow Reservoir I. Fish from this population likely have and will continue to escape into NF Spanish Creek, providing a chronic, soft introduction of grayling to the Spanish Creek watershed. MTFWP has confirmed angler reports of grayling caught in the Gallatin River and Flying D fishing guides also report numerous grayling caught in Spanish Creek. Annual electrofishing surveys have yet to capture a grayling in Spanish Creek and there is no evidence that the fish are naturally reproducing in either location.

TBD staff introduced grayling into lower Cherry Creek (below Cherry Falls and outside of the WCT restoration project area) in 2016 and 2017. A total of 25,000 fertilized eggs were stocked into lower Cherry Creek using remote streamside incubation (RSI) devices. RSIs improve hatching success and allow larval grayling to volitionally leave the incubator and enter the stream habitat.

Project Activities in 2018

To prepare for the annual spring grayling spawn at Green Hollow II, TBD netted and held several hundred grayling in early May. 205 females were spawned on May 10th, producing an estimated 264,880 eggs for grayling restoration in southwest Montana and Yellowstone National Park. There continues to be concern that there are too many grayling in the pond, resulting in smaller females and fewer eggs. Post-spawn abundance was estimated at 2,269 individuals, significantly higher than the target population of 1,300. Similar to 2015-16, approximately 208 fish were moved into lower Green Hollow Creek after the egg take.

TBD staff introduced another 20,000 grayling eggs into lower Cherry Creek (below Cherry Falls and outside of the WCT restoration project area) via remote stream-side incubation (RSI) devices. To provide the hatching grayling a more accommodating habitat and higher chance at survival once they left the RSI’s, the RSI’s were placed in a flowing irrigation ditch rather than on the stream bank, which is more typical. After flowing in the ditch for some distance below the RSI’s, the water and newly hatched grayling were diverted back into the creek. The ditch experiment worked well and will be used again in the future.

Modest electrofishing monitoring efforts in the spring and fall of 2018 failed to capture grayling in lower Green Hollow, NF Spanish, or lower Cherry creeks. Nevertheless, Flying D fishing guides and MTFWP continue to confirm angler catch of grayling in Spanish Creek and the Gallatin River.

Proposed Future Activities

TBD will continue to maintain the Green Hollow II grayling brood stock and assist MTFWP with egg takes each spring. RSI stocking of grayling will continue in lower Cherry Creek until a population is successfully established or such outcome is considered unfeasible. Grayling introductions will be considered in upper Cherry Creek once the recently introduced native westslope cutthroat trout population stabilizes. Annual monitoring will occur in waters where grayling have been introduced.