Photo: Ross Purnell

Let me admit immediately that most trout in Rocky Mountain National Park are small, and the best fishing is often at the end of a long, steep hike. If trophy-size trout and a short walk from the parking lot are what you’re after, there are better places. But if you appreciate the sounds of bugling elk instead of roadside traffic, the adventure of alpine lakes fringed with snow in July, twisted pines wracked by wind and ice, small streams bubbling through flowered meadows, gemlike greenback cutthroat trout, and the majestic scenery of some of the highest peaks in the Rockies, then this place is worth a visit.

Just looking at a map of Rocky Mountain National Park (RMNP) rivets your attention. What you see at a glance is a peppering of 150 alpine lakes and a lacework of flowing water that adds up to 450 miles of streams. About 50 lakes (360 total acres) and 150 miles of streams hold trout.

The best lakes (in the backcountry) are places where trout cruise the shoreline shallows throughout the daylight hours, feeding on sparse hatches of aquatic insects such as mayflies, damselflies, and midges, and terrestrial insects like ants and beetles that are blown into the water. If you choose the right lake—and most importantly make the strenuous effort to get there—you’ll find these trout require voracious summertime appetites to see them through the long winter.

Park Streams

The major river systems flowing out of the park—the Cache la Poudre, Colorado, North Fork St. Vrain, Big Thompson, and Fall rivers—are well-known trout streams and receive most of the angling pressure in RMNP. They hold brook, brown, and/or rainbow trout in the most easily accessed reaches near roads or trailheads. Farther upstream, sometimes above waterfalls or other natural barriers or in the tributaries, there are restored populations of native cutthroat trout. [For more detailed information on flowing waters, see “Fly Fishing RMNP Streams” at flyfisherman.com/rmnp. The Editor.]

High Lakes

While picking pockets in the lower-elevation park streams is exciting, backcountry lake fishing is the highlight of RMNP. The trout in these lakes are generally larger than those found in the streams because they don’t have to expend energy fighting the current and often have a more dependable food supply. Most of the fish are 8 to 12 inches, with 14- to 16-inch trout uncommon trophies.

This isn’t chuck-and-chance-it lake fishing—no sinking lines, float tubes, strike indicators, or patience are required. The trout hug the shoreline shallows, feeding where you can see them.

The shore is a constant source of food for high-altitude trout. Terrestrial insects fall from shore or are blown into the water from nearby rocks and trees. Hot air rises, and on hot, windy afternoons from June to September, updrafts along the Front Range carry ants, beetles, and other flying insects from miles away, depositing them in the same high cirques that collect snow in winter. Wind and wave action often congregate the floating insects near the shore.

Do not make the mistake of immediately casting toward the center of the lake—or worse yet, wading across the shallows and casting into the deep green hole in the middle. This may be a good spot for trout in the lowlands, but alpine trout usually use the deep areas only as a refuge from thick winter ice—not as summer feeding areas.

The best strategy is to approach the shore cautiously with polarized glasses and a baseball cap to block glare. In lakes with good trout populations, you’ll see trout cruising the shallows.

Trout in lakes are always on the move but they never seem to get very far. If you are observant, you’ll notice every trout patrols a territory. Some move in clockwise or counter-clockwise patterns cruising the shoreline as though it were a one-way street, some move up and down a short piece of shoreline, while others circle the limbs of a fallen tree. The territories are not large, and as they move, individual trout rarely leave your view. They leave their territory only when they are not feeding or when frightened.

When you recognize a pattern, you should cast while the trout is facing away or at the far end of its patrol. The water is clear, quarters are tight (the cast is often 20 feet or less), and a waving arm and falling fly line can send them skittering. Don’t cast at the trout—gently place your fly in the trout’s path and wait for it to come to you. Trout often accelerate toward the fly when they first see it and either gulp it while still moving or come to a sudden halt, turn away, and continue the patrol.

If the fish refuses your fly, do not rip the line off the water to make another frantic cast. Let the trout pass before you pick up for another shot. Sometimes a trout takes the same fly it refused earlier, but usually you must change your fly.

I start with something large and easy to see—like a #14 Parachute Adams—and if I encounter a picky fish, I drop down in sizes and eventually move to #16 beetles and then #18 ant patterns that are harder to see but catch more difficult fish. I’ve spent a half-hour or more on individual greenback trout, made 10 or more fly changes, and found that if I’m careful and persistent I can eventually make them an offer they can’t refuse.

On balmy afternoons with a light breeze, the trout sometimes graze for hours on whatever they find, and a careful presentation with a reasonable fly will catch most trout you spot. But it’s not always that easy.

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