Montana Fly Fishing 4 min read

DIY Guide to Fly Fishing the Sun River in Montana

Ken Sperry

Posted by Ken Sperry

August 1, 2017

Sun River Montana

The Sun River in Montana is a great fishing destination for only the most ambitious anglers. It is a remote rivers and presents multiple challenges. But for those willing to embrace the challenge, it provides some of the best fishing opportunities and some of the most beautiful scenery in all of Montana.

The Sun River provides one of the most authentic experiences of connecting with the outdoors that one could hope for, and with very few towns in the area and low fishing pressure, it is absolutely packed full of rainbow, brook and cutthroat trout that will jump at the first fly they see.

About Sun River

A glimpse of the Sun River on the edge of the Bob Marshall Wilderness in Montana. Beautiful fish and beautiful country. 

One thing that makes this river a bit of a challenge is the fact that it is used extensively for irrigation through a program of the United States Bureau of Reclamation called the Sun River Project. It is dammed at two separate points along its 130 mile length before discharging to the Missouri River, and there are two large reservoirs along the way.

One problem this creates is the instability of the water flows at different times in the year. For much of the year, a large area of the river between the dams is nearly impossible to boats because of very strong currents. These factors combined with the very few population centers near the river also mean it can be difficult to access.

While most would see these things as only problems and complications, adventurers will see them as challenges and opportunities. The irrigation of the river may mean uncertain water flows, but it also means a very high number of rainbow and cutthroat trout in the area between the dams that have nearly no fishing pressure.

The the lack of towns and population in the area may mean difficult access, but it also provides an authentic natural experience that is nearly unrivaled. While the fishing can be great, one of the best aspects of fishing the Sun River is the gorgeous scenery and proximity to true nature.

The only real problem with fly fishing the river is the lack of size to the fish. Most trout average  around 12 inches. What the fish may lack in size, however, they make up for in quantity.

There is a seemingly endless amount of rainbow and trout between the dams and an even larger amount of brown trout below the Willow Creek Reservoir. Not only are they high in volume, they are also not shy. Because of the very low fishing pressure, most will quickly jump at the first fly presented to the water.

Best Places to Fish the Sun River

Beginning in the Rocky Mountains on the eastern edge of the Bob Marshall Wilderness Complex, the North Fork Sun River and South Fork Sun River converge to create this beautiful stream.

For the first five miles after the origin of the river, it passes through two dams. The Gibson Dam and the Sun River Dam are separated by only three miles, and the water in between is nearly solid whitewater and almost impossible to fish from a boat.

For the next 25 miles, the river passes through a natural wonderland of steep canyons, tall mountains and beautiful green forests. The first part of this section passes through the Sun River Canyon, a beautiful area with more extensive whitewater, but it is much more hospitable than the area above.

Past the canyon, the river turns southeast into the high prairie where vegetation is more sparse then approaches the town of Vaughn. The water slows as it passes the town and then finally empties into the Missouri River at Great Falls, Montana.

Sun River Map and Fishing Access Sites

Map of fishing access spots on the X River in Montana

Get Directions to the Fishing Access Points shown above with the DIY Fly Fishing Map

The two forks of the river and the area above the Gibson Reservoir provide some great fly fishing opportunities than other parts of the river, and this area can be accessed through the Bob Marshall Wilderness Complex.

Once the river reaches the dams, things get a little more difficult as there are very few access points, and hiking is required to reach the river from there on. In this remote setting, the rainbows and brook trout are abundant and eager to jump at flies.

Once you have hiked a bit to reach the area between the two reservoirs, you will find many great places to fish. There are several deep pools and obstructions that provide great opportunities streamers and attractor nymphs.

Below the Willow Creek Reservoir, fishing is a bit more difficult as the trout are more sparse in this area. However, there will still be a fair amount of brown trout for and lots of northern pike.

Sun River Flow and Current Conditions

Sun River at Simms MT

  • Temperature: 59 ° F
  • Streamflow: 191 ft³/s
  • Gage height: 2.64 ft
Temperature GraphStreamflow GraphGage height Graph

Best Time to Fish the Sun River

The best time to fish the Sun River is in spring time when several hatches will have the trout jumping. Early spring provides great opportunities, but it can be uncomfortable to hike to the river when it is still cold. This is also a great time for the river since the runoff will have very little effect by this point in the year.

Various hatches will continue to bring the fish to the surface all the way up to late summer. Beginning around August, it is best to use hoppers since the Sun River flows through terrific hopper country once it leaves the mountains. Late summer to early fall continue to see good fishing, but things will tail off around late September. Past this point, there will still be some brown trout available, but little else.

Sun River Fishing Tips

Dry flies work great throughout much of the river, especially the area past the canyon and before Willow Creek Reservoir. Using standard dry flies like elk hair caddis and parachute Adams will show success here, but it may be difficult to catch the larger fish with these.

The biggest trout can be caught using streamers and attractor nymphs in the deep pools along the banks of this area and around embankments throughout the river. Sinking lines with weighted flies are best for these deep areas. Of course, hoppers could always be a good option, especially in mid to late summer.

A 9-foot 5-wt fly rod with floating line is perfect for fishing dry flies and small nymphs on the Sun River. For larger nymphs and streamers a 9-foot 6-wt with a sink tip fly line makes life easier. A tapered 9-foot leader, with tippet size 3X to 6X to match the flies you are throwing, is pretty standard.

Looking for more places to fish in Montana? Check out our DIY Guide to the Best Fly Fishing in Montana.