Fishing Big Rivers

Cracking the Code

Figuring out Montana’s massive trout rivers when you’re accustomed to fishing small streams. By Jeff Erickson

This story is featured in Montana Outdoors May-June 2014 issue

"I’ll bet those guys are from the Midwest,” said Mary. “Look how small their nets are. And I hope they have enough backing on their reels.” My wife and I were walking along a Missouri River side channel near Craig, watching several anglers work a pod of forearm-length rainbows.

It was the peak of the July caddis explosion, and hordes of bugs hovered above the water and bankside willows. The caddis galaxies, mixed with scattered Pale Morning Dun (PMD) mayflies, had stoked a feeding frenzy. The guys with the tiny landing nets—who we later learned were Midwesterners—worked the hungry pod to no avail. They couldn’t hook a single trout and were obviously frustrated. Thinking back on my own history of learning how to fish the Missouri and Montana’s other big trout rivers, I knew exactly how they felt.
At least those anglers had located fish—which is more than I could say for myself during many initial visits to the state’s sprawling rivers.

One of the best life decisions my wife and I made was to move from Minnesota to Montana in 1994. Rivers like the Missouri, Bighorn, Yellowstone, and Kootenai offer oversized trout that the Midwest’s spring creeks can rarely match. After arriving here, we began to regularly visit the Missouri’s fertile stretch between Holter Dam and Cascade. Lacking a drift boat, we walked and waded, having no idea of the vast learning curve ahead of us. We went from fishing streams that often ran at less than 50 cubic feet per second (cfs) to a tailwater leviathan running at 3,500 to 5,000 cfs during typical midsummer flows. It was like fly-fishing on the Pacific Ocean.
Our first Missouri excursions were humbling busts. I was continually frustrated by the hard-to-read river, its hurricane-force winds, and the selective, uncooperative fish.

But eventually I began cracking the code of the Missouri and other big rivers and started hooking fish. What follows is the insight I’ve gleaned from two decades of fishing and hundreds of outings. By comparing big Montana rivers to the small creeks back home, I’ve discovered many similarities but also several essential differences. The trick has been to learn when to fish a big river like a small stream, and when to fish it with a completely different approach.

Break it down
Remember your first term paper in college? If you were anything like me, you became overwhelmed by the information you had to absorb and then organize into a coherent essay. It took me years (and an embarrassing number of incompletes) to learn how to break a large writing project down into manageable parts that I could tackle piece by piece.

The first time I saw the Missouri, it reminded me of those college research project nightmares. The river was so big, and all the water looked so similar. I was paralyzed, not knowing where to begin.
Eventually I learned that not all water on big rivers holds fish. Instead of being scattered randomly throughout, as I once thought, trout concentrate in key areas. The trick is to find those spots.
As soon as I arrive at a river, I begin surveying the water and surrounding landscape. As I calmly look upstream and downstream, I see that what initially appeared to be a vast and featureless expanse has many definable and fishable characteristics. Yes, I’m still tempted to start casting randomly, eager as usual to get my fly on the water. But I’ve learned the importance of examining the river beforehand so I don’t flail away fruitlessly like in the old days.

Island life
Two critical features of any big trout river are its islands and side channels. I focus most of my fishing in these areas and will happily spend an entire day exploring an island complex, flushing deer, geese, and beaver as I wade the shallows looking for fishy water.

Trout love side channels between islands and the main riverbank. The narrow waters provide spawning areas, habitat diversity, and shelter from the powerful main current. For anglers accustomed to fishing creeks and streams, side channels are familiar, reassuring places to start.
Channels often hold big trout. Many anglers from elsewhere assume Montana’s trophy browns and rainbows only hunker down in the biggest water, in the middle of the main current where wade anglers can’t reach. In fact, trout over 20 inches often hang out in channels the size of small streams.
Island tips and tails are productive places to fish. Trout often lie in current seams on either side of the tail, as well as farther down where the two current lines converge.

Immediately below the tail there is often a calm area. There trout can avoid current while feeding on aquatic insects that accumulate during and after a hatch. After sunset, trout also cruise the shallows just off the tail looking for baitfish, making that water a good place to throw streamers.

Upstream tips of islands may not appear to be productive, but they often hold fish. Trout frequently rest in current seams and ripple lines created where channels sweep past the tip. During hatches, gravel flats that often fan out above or below islands can be alive with rises. One July evening, in such a spot on the Missouri, I landed a 19-inch brown and then—10 minutes later—hooked and netted an explosive 19-inch rainbow.

Just as the banks of small streams often produce good trout fishing, so do the banks of island channels. Terrestrial insects such as ants and beetles tumble off steep cutaway banks, while floating bugs are driven to bankside shallows by wind and current. Some of the biggest side-channel fish may be holding in just several inches of water, feeding on Blue-Winged Olives, PMDs, Tricos, midges, caddis, or grasshoppers.

Islands also act as windbreaks. When gales strafing the main river put fish down, high side-channel banks create calmer zones where trout often continue rising. Anglers can use these sheltered areas to fire off more accurate casts—and avoid banging the back of their skull with a heavily weighted Woolly Bugger cast in heavy winds.

Stick to the shallows
Outside bends are where big rivers and small streams are worlds apart. On streams, outer bends are smart places to work a fly, especially where current moves through undercut banks or other cover. But on most rivers, the massive volume of water ripping along an outside bend can be too heavy and deep to fish effectively, especially for wading anglers. On a big river like the Yellowstone, you can step off the bank on an outer bend and immediately be in over your head.

Inside bends are just the opposite. On small streams, this inner part of the current is often too shallow and lacks enough overhead cover to attract trout. Though the same hydraulic forces shaping inside bends on smaller streams also apply to larger rivers, the fishing opportunities here are far better. Big river trout often rest comfortably in the featureless shallow slack water of inside bends. There they can avoid battling the main current while still finding plenty to eat, then dash to deeper water to escape danger.

One of the biggest mistakes I see other anglers make on big rivers is to ignore shallow water. I understand the error. In much of the United States, including small streams in Montana, anglers have learned that trout congregate in deep, shaded holes and runs, such as under overhanging trees or out from large limestone outcrops. But on rivers, the largest fish often hang out in the shallowest spots. Often I’ve seen anglers standing in 2 feet of water that I know from experience holds big trout, casting out to 20-foot depths where, on big rivers, fewer fish lie.

One way to read shallow water is to stare at it for several minutes or more, without casting. A trout’s conventional rise to a dun on the surface will be fairly obvious, but be alert for more subtle signs: a slight ripple, a flash of a fish, a slowly waving fin, a nose bulging the surface, or fleeing minnows. Big river trout are in the shallows because they’re hungry and that’s where the food is. Look for signs.
Don’t make the mistake of leaving shallow water once the sun goes down. The best prospecting often occurs immediately before and after sunset. Once light leaves the water, trout lose caution and are more likely to attack a fly in skinny water. Bring a headlamp and stay for the river’s encore.

Seams—places where two currents meet—are another feature that small-water trout anglers should always look for on big rivers. The friction causes the river to slow and give fish places to rest while feeding off the conveyor belt of protein floating past in the swifter current.

Look for seams out toward the main current from bankside shallows. Seams also exist between the shallows of inside bends and the deeper main current. These current lines are especially productive in midsummer on slow, fertile rivers like the Missouri or Bighorn. When inner bends become weedy this time of year, trout hold along the edge of the vegetation.

Just like home
Anglers overwhelmed by a big river’s volume should also keep their eyes peeled for the same types of riffles, runs, eddies, and other structure that hold trout in creeks. The difference is that these features on big rivers may be spaced hundreds of yards or farther apart. Or they may morph into each other more subtly than on a faster, smaller stream. While walking 10 minutes along a mountain brook, an angler might encounter a dozen different riffles, runs, and pools. On larger, slower rivers, you may have to hike for half an hour or more just to find one of these familiar fishing features.

Just like on small streams, big river trout gravitate to riffles for abundant insects, enhanced dissolved oxygen, and overhead protection provided by broken water. Like on many trout streams, the zones where riffles drop off into runs are also prime spots to drift a nymph. During a hatch, the entire surface of a long run may be punctuated with rises.

The mouths of tributaries running into large rivers are trout havens, especially during spring and fall spawning seasons. Boulder-strewn pocket water also can be fruitful. The same goes for gravel bar drop-offs, overhanging willows, or submerged logs. If you can’t find obvious fish cover, look harder for subtleties: small rocky points creating a ripple line, fences or beaver lodges intercepting the river, or slight depressions in the bottom.

Deep holes also hold fish, but while a hole on a stream might be 8 feet deep and fishable, on a river it could go down 30 feet or more, making it impossible to fish without a boat—and difficult even then.

Instead of holes, I look for eddies. Sometimes I’ll emerge from those massive whirlpools slathered in weeds, mud, and rotting bugs and holding a football-sized brown for my efforts. With all the debris circling in that purgatory of current, you might think you’re fishing for carp in an urban backwater (in fact carp do often hold in Montana’s big river eddies). The whirlpool action of an eddy captures and holds vast amounts of insects—along with mats of vegetation, lost bobbers, discarded worm containers, and other unsightly debris. But the trout don’t care about this, and neither should you.
Big river eddies are like a secret nightclub where the action keeps rocking long after the party has shut down elsewhere. Trout take up position in an eddy and feed all day—even when there’s not a rise anywhere else on the river—and well into the night. One challenge for fly anglers is getting a drag-free drift in the tricky currents, which often go several directions at once. Another is to keep the floating vegetation and other scum off your fly and tippet, usually done with tight, whiplike false casts.

Some of the best times to fish eddies are on cool, damp days, when the wings of Baetis and other mayfly duns stay too damp for the insects to readily fly off the surface. The flies are trapped in the circulating current, and trout move in and feed aggressively.

Trout waters big and small share many similarities. That’s because trout are always looking for the same things: safety, food, and cold, oxygenated water. The big difference between Montana’s oversized rivers and a familiar “crick” is that the fishy features are not nearly as obvious. You have to look harder and cover more ground. But the trout are there.

Big rivers can be a lot like those Bev Doolittle paintings, where the ponies are hidden in the background yet remain in plain sight. When fishing a river, you can stare and stare and see nothing other than miles of uniform, seemingly fishless current flowing past. Then you spot a shadow or slight current undulation that reveals itself as a trout or a place where a trout likely lives. Even more amazing, you realize it’s been there all along.Bear bullet

Helena resident Jeff Erickson is a freelance writer and the Rocky Mountains field editor for Northwest Fly Fishing.

Cross carefully

It’s pretty hard to drown while wading a small stream. But that’s not the case with Montana’s big rivers. The level of danger grows with the water’s size and intensity. Sometimes, while wading way off the downstream tip of an island, I remind myself that a fall would quickly put me in the middle of the river, a football field from either bank. When gravel starts ripping loose from under my wading boots, I start heading back upstream to shallower water. One tip when contemplating a dicey crossing is to visualize what would happen if you did fall in and how you would respond. Your safety will be greatly enhanced by wearing a wading belt cinched tightly around your waist, and using a wading staff. If you do get swept into the current, remember to float calmly on your back—feet downstream—until you can work yourself over to shallower water. —JE

Islands and bends