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Fly Fishing Rocky Mountain National Park

Hiking for native greenbacks in Colorado's Rocky Mountain National Park.

Fly Fishing Rocky Mountain National Park

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. 

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. 

greenback cutthroat trout, rocky mountain national park, fly fishing
A stunning greenback cutthroat trout. (Ross Purnell photo)

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.

Day Hikes

Most fly fishers day-hike to the high lakes. If you are in reasonably good shape and travel light, you can easily make a 5-mile hike in two hours. If you leave the trailhead at sunrise or earlier, you can be lakeside before the morning sun hits the water and have all day to fish. The park headquarters are 7,840 feet above sea level and many of the lakes are at between 9,500 and 11,000 feet, so expect a steep hike on any excursion.

Fern, Sandbeach, and Ouzel lakes are excellent greenback lakes less than 5 miles from a trailhead. Fern Lake is also a popular day hike for nonanglers, and around lunchtime you may see hikers having a picnic. If your wife enjoys the outdoors but doesn't like to fish, these lakes are perfect places for her on a warm summer afternoon.

From the Glacier Gorge trailhead, Mills Lake, The Loch, Glass Lake, and Sky Pond are all good fishing lakes with spectacular views. The trail to Sky Pond is one of the most scenic hikes in RMNP. It passes two waterfalls Alberta and Timberline and ends at a high cirque fringed by Taylor Glacier and the jagged spires of Taylor Peak. The fishing is the dessert after a fine meal of spectacular hiking. The deep pools of Glacier Creek upstream of The Loch are also worth fishing.

Bring fleece and waterproof jackets on any trip to the high country. The Denver weather forecast is meaningless at places like Thunder or Hayden lakes, where it can be 40 degrees and windy while it is 90 degrees and sunny in Denver.

Hiking at higher altitudes increases the chance of dehydration, severe sunburn, mountain sickness (headaches, nausea, dizziness), and the aggravation of pre-existing medical conditions. If you begin to feel sick or experience any physical problems, descend to lower elevations.

Afternoon thunderstorms are common. When black clouds roll in, stop fishing, put down your rod, and take cover below the treeline until the storm passes.

Always hike with a buddy, and let someone know where you'll be hiking and fishing, and when you are expected to return. Cell phones have limited coverage in the park so don't expect them to work.

Bring twice as much food as you think you need for a day trip and at least 64 ounces of water to prevent dehydration. Water is heavy, and filter systems are too slow when I'm really thirsty, so I use Aquamira water treatment drops (or similar). It's a tasteless treatment that allows me to drink as much stream or lake water as I want without carrying water on the trail.

float tubes, rocky mountain national park, fly fishing, stillwater, lake,
Always hike with a buddy, and let someone know where you'll be hiking and fishing, and when you are expected to return. Cell phones have limited coverage in the park so don't expect them to work. (Ross Purnell photo)

Footwear is the other most important consideration. Wear two pairs of socks. The liner socks should be thin, tight, synthetic material that wicks moisture outward. This layer serves as a buffer. Think of it as an extra layer of skin because if you don't wear it, you'll sacrifice your own skin with blisters.

The outer sock should be thick and cushioning like heavyweight Capilene or SmartWool to help protect your feet at friction points including the back of your heel or the outside of your big toe. A two-sock system protects against blisters even when your shoes are soaked.

I wear lightweight hikers with a stiff sole and aggressive tread. In most cases, the trails are smooth and well maintained, and you don't need heavy, ankle-high hiking boots. Waders are too bulky and heavy to be worth the effort for a day trip, and are also impractical for overnight trips when you also must pack a tent, sleeping bag, and food.

Overnight Camping

The least-visited and most desirable lakes in RMNP are too far from the trailhead for a day trip. Luckily these lakes usually have nearby backcountry camping. Backcountry camping permits are available online. A backcountry permit is valid only for specific sites on specific dates, so you should submit your reservation several months in advance to make sure you get the site you want.

The campsites have primitive toilets. All other waste must be packed out. Complete rules and regulations are available online or from park rangers when you pick up your permit at the park office.

Sandbeach Lake on the shoulder of Mt. Meeker is a possible day trip, but better for a night or two since the trail is steep and the lake is large enough (17 acres) to explore for more than a day. The trail to the lake does not follow the outflow, and as a result, Sandbeach Creek is relatively unfished and filled with native cutts.

Pear Lake is a difficult 7-mile hike with excellent campsites and frequent evening rises through the summer. There is no backcountry camping available at nearby Hutcheson lakes (9 miles from the Finch Lake Trailhead in Wild Basin), making Pear Lake an excellent base camp for forays to Lower, Middle, and Upper Hutcheson lakes.

There is another good base camp at Lawn Lake, a 6-mile hike that seems to take forever because of the constant attraction of the Roaring River at trailside. Nearby Big Crystal Lake at 11,500 feet above sea level and more than 25 acres is at the base of the Mummy Range, but the fishing is so good that there's rarely opportunity to gaze at the impressive array of peaks.

In the Colorado River basin, good backcountry camping and fishing for native Colorado River cutthroat is available at Timber Lake, Haynach Lake, Lake Nanita (camp at North Inlet), and Lake Verna (with day trips to Spirit, Fourth, and Fifth lakes).

This list of well-known favorites only scratches the surface of the lake fishing in RMNP. They are easily accessed by well-marked and maintained trails.

But there are other lakes that are rarely visited and veiled in mystery. Adams Lake in a cirque above a valley known as Paradise Park is on RMNP's list of catch-and-release waters, but it's in a no-camping area miles from the backcountry campsites at Cat's Lair.

Arrowhead Lake in the Gorge Lakes group is on the same list of catch-and-release waters but there is no trail. There is a single campsite at nearby Little Rock Lake, but the only way to get there is to park at the Rock Cut parking area on Trail Ridge Road (11,800 feet), eyeball the lakes on the opposite side of Forest Canyon, clamber down into the valley below, cross the Big Thompson River, and then regain the 2,000 feet of elevation.

Keep in mind that many lakes such as Chasm Lake at the base of Longs Peak are barren. Other lakes or parts of lakes are closed to fishing to protect recovering greenback populations. Refer to the National Park Service's RMNP fishing brochure for rules, regulations, and a complete listing of lakes known to contain trout. The brochure is available at most ranger stations and online at

Seasons at Rocky Moutain National Park

Ice-out on alpine lakes is difficult to predict, and depends on the severity of the preceding winter, the elevation, and exposure to the sun. Most lakes near 9,000 feet become ice-free sometime in June, or earlier, but some higher lakes do not thaw completely until July.

While the shoulder seasons of June and September can offer fine fishing, the pleasant temperatures and dependable summer fishing make July and August weekdays the best choices for most visitors.

Camping Logistics

Nights can be cold at these high lakes lows of 40 degrees F. in July or August are not uncommon at 11,000 feet. Bring a three-season sleeping bag and a change of clothes in case you get wet. A sleeping pad is also a requirement not a luxury as it keeps you warm. A waterproof tent that can stand up to the wind is also a necessity.

All the backcountry sites in RMNP have bearproof food containers to store your food night and day. Greenback lakes are catch-and-release fisheries, so you cannot eat trout. If your heart is set on a fresh trout dinner, consider lakes with nonnatives such as Peacock Pool, where the limit on brook trout is 18 per day, and you can easily catch that many by noon.

Todd Hosman's book Fly Fishing Rocky Mountain National Park (Pruett Publishing Company, 1996) will help you plan your trip. You can get a printed version of the same map at the park gates, but backcountry anglers should get the waterproof Trails Illustrated Map of RMNP published by National Geographic. It provides topographical detail not present on the National Park Service map, and shows all the major hiking trails and backcountry campsites.

Ross Purnell is the editor and publisher of Fly Fisherman magazine. 

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