Rocky Mountain National Park has 50 backcountry trout lakes to explore and miles of stream fishing. The park is the world's most important refuge for rare and beautiful greenback cutthroat. Ross Purnell photo
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 at the edge of the treeline wracked by wind and snow, 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.
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 or from miles away. 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 drive the floating insects near the shore where they congregate.
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.
The edges of lakes are where the food and the trout are most concentrated.
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.
These trout live in the high country but are not always easy to catch. 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.
I remember an evening at Spruce Lake that started out with easy fishing--and then the #32 midge hatch began. As the hatch progressed, the trout began to feed more aggressively, yet became harder to catch. In the last hour of daylight, the entire surface of the lake was dimpled by the head-and-tail rises of hundreds of trout. Amidst this feeding frenzy, my buddy and I caught only a few smaller trout using #24 midge pupa imitations on 6X tippets, but the trout got the better of us.
Flies. You should carry bushy, high-riding drys (Humpys, H&L Variants, and Elk-Hair Caddis) for RMNP streams, but the flat, glassy lakes demand flush-floating patterns such as #12-18 Parachute Adams, #14-18 CDC & Elk, and #14-18 thorax-style mayfly imitations with the hackle trimmed flat on the bottom. I've never seen a full-blown mayfly hatch on a lake above 9,000 feet, but mayflies are always around, and the trout recognize them.
Midges are the most important aquatic insects, and sometimes actually produce a real hatch with selective feeding. I bring my San Juan River fly box to RMNP, as the flies are often similar. Midge pupae are #14-18 early in the season and by August and September become nearly microscopic. Adult midges are correspondingly small and are usually black, cream, or tan. A simple thread body with a single turn of hackle is as good as anything else I've tried.
Also important are low-riding terrestrial imitations such as foam #14-18 beetles, #14-18 flying ants (red, tan, and black), and small #10-12 grasshoppers. (The higher you get, the less important grasshoppers become.) Carry Beadhead Pheasant-tails and Hare's Ears (#14-18) in case you want to try a dropper.
Rods. You need a 9-foot, 5-weight rod if the wind comes up in the afternoon. Bring it along, but hope you never use it. If it gets windy, it becomes difficult to sight-fish, and a 5-weight is overkill on a 10-inch trout. Bring the smallest, lightest rod you have available.
You are often crouched, or casting around trees or other obstacles, and rarely cast more than 30 feet. A light line lands quietly on the water, spooks fewer trout, and allows a small trout to actually bend the rod a little. It's also more fun, and even a "large" 12-inch trout can be derricked to the hand and safely released in 30 seconds with a 1-weight rod. Many of the lakes are protected from the wind, and while it can be breezy in the afternoons, mornings and evenings are often calm.
Ross Purnell is the editorial director of Fly Fisherman magazine. He used to live near RMNP in Fort Collins, Colorado, and now lives in Pennsylvania.
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