Flowing out south-central Montana’s impressive Bighorn Reservoir, the Bighorn River is truly a flyfisher’s paradise. Considered by many to be one, if not the most productive trout rivers in the world, the Bighorn hosts an average of 6000 trout per mile to back up its swagger. To add to this astonishing figure is the fact that the average size of a Bighorn trout ranges between 16-18" with 5 and 6 pound lunker caught with striking frequency.

The river’s primary attraction is the 13-mile stretch beginning below the Yellowtail Dam at the town of Fort Smith. Ideal flows on this length fall between 2,000 to 5,000 cfs but fishing is still productive up to 7,000 cfs. Anything above this benchmark signals a swollen torrent with difficult fishing. The river character is not unlike that of an enormous spring creek, with undulating weed beds, deep holes, undercut banks, and occasional riffles. River access is few and far between and much of the adjacent land falls under the ownership of the Crow Indian Reservation. This consideration, along with the thick currents, makes the Bighorn a float river. The wading angler can carve out some fishable water, but he is at a severe disadvantage to the boater.

The river can be floated in segments as access points spread themselves out along the rivers length: Yellowtail Dam/Fort Smith ("Afterbay Access"), 3 miles ("Three Mile Access"), 10 miles ("Bighorn Access"), and 14 miles ("St. Xavier Bridge Access"). Even the novice boater can float this section without much problem as the surrounding terrain is relatively flat resulting in a pleasant, gentle, consistent current. Below the 14-mile access, the Bighorn slow its pace and loses some its water quality and clarity, resulting in lower numbers of trout. Despite this, locals claim that this stretch, which continues to mile 29 ("Two Leggins Access"), harbors the largest of the river's trout, giant nocturnal browns tucked along the undercut banks and nosing in the deep holes.

When and How to Fish

The Bighorn is a veritable insect producing machine keeping its resident browns and rainbows fat and happy. The primary hatches include the Caddis, Trico, Pale Morning Dun, Little Yellow Stonefly, and Baetis, all of which fall in the size # 16-20 range.

Baetis fishing can be productive from April to early June and then again in the fall between September and November. The hatches generally last from 11 a.m. to 5 p.m. with the highest intensity occurring at mid-day. Olive cripples or Parachute Adams will take fish on the surface, but the best fishing is to be had scouring the bottom with a weighted Hare’s Ear or Pheasant Tail nymph.

Mid-June marks the emergence of the Little Yellow Stone whose various imitations (Stimulator, Elk Hair Caddis, or Little Golden Stone nymph) will take fish consistently in riffles. PMD’s begin their emergence cycle in mid-July and remain active for about a month. During this period, nymphing with a Red Squirrel nymph can be very productive, as well as a PMD cripple on the surface. Evening spinner falls can be explosive and best results are achieved with a Rusty Spinner. As the little Yellow Stone hatch begins to taper-off in late July, the Tricos begin to take command followed shortly thereafter by the Black Caddis. The tricos (large by most standards) are an important hatch on the Bighorn as they lure up the monster rainbows after having recuperated from their spawning rituals. The Black Caddis hatch in August and September can be downright electric with the majority of the feeding occurring in the evening and deep into the night. In the off-season, or to break the rhythm a bit, midges, scuds, and tube-worms can be fished effectively throughout the year.

Fishing deep on the Bighorn means 9-foot 4-6x tippets, one to two lead twisties, and a strike-indicator. Given the numbers of fish and the presence of weed-beds, long, arduous casting is not really an advantage. 35-45-foot casts with a 9-foot 6-weight with floating line should do the trick.

Despite the intense pressure, the Bighorn continues to live up to its preeminence in the flyfishing annals. Even a slow day on the Bighorn is equivalent to great day on most other rivers. That being the case, you can only imagine what truly great day must be like. If you enjoy the expansive breadth of Big Sky Country, emerald green currents, and the true likelihood of hooking into a giant two-foot rainbow, the Bighorn is the river for you.l