Montana Fly Fishing 4 min read

DIY Guide to Fly Fishing the Red Rock River in Montana

Ken Sperry

Posted by Ken Sperry

February 4, 2024

Red Rock River in Montana

Planning a fly fishing trip to Montana? This state is known for having some of the best and most productive rivers and lakes in the country. There are countless places to go fishing, including the Red Rock River.

Whether you are new to the hobby or you have fished for years, this river has a lot to offer. In the DIY guide that follows, you’ll learn what you need to know about this river, the type of fish you can find, and more.

About Red Rock River

An aerial view of the Red Rock River in Montana

Red Rock River is located in the southwestern part of Montana not far from the border with Idaho. The roughly 90-mile river flows through remote areas in the Centennial Valley and past the Centennial Mountains.

The Red Rock originates from the Lower Red Rock Lake in Red Rock Lakes National Wildlife Refuges and terminates at the Clark Canyon Reservoir Dam. Below the dam is the famous Beaverhead River.

Along the way the Red Rock River flows through the Lima Reservoir. The primary purpose of the reservoir is for irrigation resulting in unpredictable water releases that adversely affect the river at times.

Type of Fish in Red Rock River in Montana

You will find a range of fish species in the river. Depending on where you are fishing, you will find that certain types of fish tend to be more plentiful.

Along the upper stretch, you can fish for brook, cutthroat and rainbow trout, mountain whitefish, and Arctic grayling.

Below the Lima Reservoir, you will find brown and rainbow trout including some lake fish that run up from Clark Canyon Reservoir. Your best shot at lake-run rainbows is below Kidd, Montana as your get nearer to the Reservoir.

Red Rock River Map

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

Best Places to Fish the Red Rock River

Unfortunately, there are no Montana designated Fishing Access Sites on the river and a lot of river runs through private property.

There are several sections that run through state property and BLM land that provide public access, including:

  • Outlet of Lower Red Rock Lake
  • Below Lima Dam
  • BLM land parcels further downstream of Lima Reservoir

There are also a number of bridge crossings that provide access provide you remain below the high-water mark.

Best Time to Fish the Red Rock River

The season for this river is from the third Saturday in May to November 30.

  • Spring is a fantastic time to fish the Red Rock River except during runoff. This is the primary spawning season for rainbow trout and when you will find most of the lake-run rainbows in the river above Clark Canyon Reservoir.
  • Summer is also a popular time to fish Red Rock River unless it is a dry year when portions of the river below Lima may be closed.
  • During the fall, you have a shot at some larger brown trout as they make a spawning run up river from Clark Canyon Reservoir, typically between September and November.

Stream Flow and Current Conditions

Be sure to check the stream conditions before heading out to fish the Red Rock River. The USGS stream gauge below Lima Reservoir near Monida, MT provides a good indication of current conditions.

The graph below shows the stream flow (discharge) for the past 7-days. If flows are considerably above or below historical norms (yellow triangles on the chart) then fishing conditions maybe not be ideal.

Red Rock R bl Lima Reservoir nr Monida MT

  • Streamflow: 293 ft³/s
  • Gage height: 2.62 ft
Streamflow GraphGage height Graph

Best Flies for Red Rock River

Most anglers will agree that fishing dry flies along the upper section tends to be a good option. Standard patterns can work well, as the fish here tend to be eager to bite. However, using attractor patterns can work well, too.

The lower stretch of the river works well for dry flies, as well. Some good options can include Parachute Adams, Elk Hair Caddis, and Pale Morning Duns.

Grasshopper flies can work well, particularly at the start of July. This is when the grasshoppers tend to get active in the area.

Here is a list of general fly pattern recommendations for the Red Rock River:

Dry Flies

  • Yellow Sally (#12 – 16)
  • Yellow Humpy (#10 – 18)
  • Parachute Sulphur (#14 – 18)
  • Parachute Adams (#12 – 22)
  • Light Cahill (#10 – 18)
  • Elk Hair Caddis (#8 – 16)
  • Yellows Stimulator (#8 – 14)
  • Chernobyl Ant (#8 – 12)
  • Griffith’s Gnat (#16 – 24)


  • Pheasant Tail (#12 – 20)
  • BH Hare’s Ear (#12 – 20)
  • Rainbow Warrior (#14 – 22)
  • Pat’s Rubber Legs (#4 – 12)
  • Golden Stonefly (#6 – 10)
  • Tellico Nymph (#12 – 18)
  • Zebra Midge (#16 – 22)
  • WD40 (#16-20)
  • Y2K Egg (#12 – 16)


  • BH Wooly Bugger (#2 – 6)
  • Sculpzilla (#4)

Gear Recommendations

A 9-foot 5-wt fly rod and matching fly reel with floating line is perfect for fishing for trout on the Red Rock River. A tapered 9-foot leader, with tippet size 3X to 5X to match the flies you are throwing, is pretty standard.

Red Rock River Fishing Report

There currently are no area fly shops that regularly publish a Red Rock River fly fishing report and update on current conditions.

Fishing Regulations

The state of Montana requires that all people who are 12 years of age and older have a valid fishing license. There are resident and non-resident sport fishing licenses available.

You can purchase a Montana state fishing license and learn about the most current regulations through the Montana Fish, Wildlife & Parks.

Trip Planning Tips

The nearest towns from which you can easily reach the various portions of the river are Ennis or Dillon in Montana and Island Park in Idaho. You can find places to stay in those towns, or you could look for camping spots in the area.

There are access roads off Red Rock Road that can help you access different parts of the river that are on public land. Lima Dam Road, out of Lima, can provide access to the river, as well.

Getting to most areas is easy by driving and taking a short walk. However, there are some portions, including the upper part of the river, that will require some hiking.

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