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An Unconsidered Realm

Wyoming’s Snake River is cutthroat country. The watershed consists of dozens of tributaries, spring creeks, and lakes and is considered one of the strongest native fisheries in the United States. The drainage has drawn anglers from across the globe due to its reputation - rightly or wrongly – for unparalleled dry fly fishing for rising cutthroats. Perhaps nowhere in the continental U.S. do fly fishers have as great a chance to cast to nothing but native trout.

Lesser known is the fact that the drainage also holds small, but stable, populations of other species. Brook trout and grayling can be found in several high country lakes and creeks. Brown trout populate the upper Snake in strong enough numbers that anglers are not necessarily surprised to hook a couple in a day’s outing. And Kokanee salmon make late summer runs up select streams feeding Palisades Reservoir.

All of these species add a bit of diversity for fly fishers looking for something a little different from waters dominated by Snake River fine-spotted cutthroat. Without question, the strongest population of non-native trout within the watershed is lake trout. Often referred to as mackinaw, lake trout in this part of the Rocky Mountain West have gained a strong following amongst local and visiting fly fishers. Perhaps the most popular is Jackson Lake. It is the largest body of stillwater in Wyoming’s Snake River drainage.

The Snake River, which flows into the lake from Yellowstone National Park to the north, leaves it via Jackson Lake Dam. The dam acts as a conduit whereby mackinaw can access the Snake River downstream. The spillway and tailwater below the dam are one of those few places in the world of fly fishing where lakers can be targeted on a trout stream. As with those anglers who cast to mackinaw on area lakes, this little fishery has developed a small but dedicated cult following. And like fly fishers the world over who target specific species in specific waters, they have developed unique tactics and strategies for catching lakers in rivers where other trout dominate.

Enter the Lake Trout

Lake trout were first introduced to the Snake River drainage in the 1890s. Using hatchery stocks from the Great Lakes region, the federal government stocked them in previously fishless Lewis and Shoshone lakes in Yellowstone National Park. Heart Lake further to the east was also stocked at the same time. Both the Heart River and the Lewis River flow into the Snake just downstream of the river’s headwater creeks. There is evidence that lake trout used these streams for downstream migration to Jackson Lake by the early 1900s. Mackina were firmly established in the lake by the 1930s when the Wyoming Department of Game and Fish (WDGF) began supplementing the population. The stocking program was so successful, and the fishing so popular, that Charles Wort had a well-established fishing lodge on the lake’s southeast shore by 1940. WDGF’s supplementation – numbering anywhere from a low of 17,000 to over 300,000 mackinaw annually – continued until 2006.

100 years later, Jackson Lake has developed into a thriving sport fishing venue attracting thousands of anglers a year. Trophy lake trout are the featured specie. In fact, the Wyoming state record mackinaw – 53lbs – was caught in the reservoir. While other waters in Yellowstone and Grand Teton National parks contain strong populations – including Jenny, Leigh, and Phelps lakes - none of them have the drawing power of Jackson Lake.

Despite the stocking of hundreds of thousands of rainbows, browns, and brook trout over the years, few invasive species have gained even a toehold on the Snake River itself or its tributaries. Non-native trout make up less that 1% of the total abundance on the stream and its tributaries. Fine-spotted cutthroat rule the watershed.

But the five mile reach below Jackson Lake is different. Where much of the river and its tributaries average over 16 feet/mile, this tailwater section pitches at only around 4 feet/mile. Parts of it even feel devoid of current, much like a body of stillwater. It seems conducive to the survival of almost any species of trout. Here, browns can be caught with much more frequency. So, too, can lake trout. Releases from the dam most years are anywhere from 350cfs during the winter months to over 7,000cfs in early summer. Regardless of the flows, lakers can make their way out of the dam and into the river any month of the year. They are caught on this section of water year round.

Fishing for Lakers on a Trout Stream

The low gradient, uniform stream bottom, and relatively small cobble size all combine to make this portion of the Snake ideal for wading. It is by far the most popular way to fish this tailwater reach. Much of it can be accessed by just pulling into one of several parking areas, gearing up, and walking a short distance to the river. More driven anglers willing to bushwhack and walk a little longer can fish its entirety.

Nonetheless, boats are often employed and can provide advantages not offered through wade fishing. While the river is slow moving, it is wide compared to the rest of the Snake. Some parts are a solid 70 yards from bank to bank. At high flows, depths within casting range of choice lies can be upwards of 12 feet. Other pieces of prime holding water can’t be touched from the bank due to intense vegetation growth that will snag flies and leader on the back cast. A watercraft of some kind is your only option in these cases. The relaxed flow and low grade means an anchor will hold almost anywhere. Some who man the oars as their boat mates fish find it worthwhile to row back upstream if a hook set is missed on a larger specimen. This is altogether impossible on most of the Snake due to fast currents and high gradient. It is completely feasible on this reach.

It is important to note that motors are prohibited on the Snake River in Grand Teton National Park. If you launch your watercraft at Jackson Lake Dam, you will be floating down to the next take-out at Pacific Creek.

Lake trout are found in their highest numbers within the first half mile immediately below the spillway. They reside here alongside cutthroats, browns, and whitefish. It is possible to fish this portion of the river and catch as many or more mackinaw than other species present. Their abundance gradually decreases with each passing mile downstream. They are still present, but caught with a bit less frequency. Four and a half miles below Jackson Lake Dam, Pacific Creek enters the Snake as its first major tributary in Grand Teton National Park. The tailwater reach of the Snake (and really the only part of the stream that can be classified as tailwater) ends. The gradient increases significantly and intensifies further downstream. Lakers, as well as every other species of trout other than cutthroat, become almost non-existent.

Streamers are an obvious choice for lake trout. They are fish eaters at heart and their caloric intake is composed almost exclusively of forage fish when they cross the 20 inch mark. I tend to use the same patterns I employ on area stillwater – small to moderately sized baitfish imitations like Rickard’s Seal Bugger, Chicklets, Clouser Minnows (sparsely dressed), Booty Call Minnows, Slump Busters, and Mohair Leeches. My line choice and retrieval rate and tempo varies with the water I am fishing. Most water where I find lake trout have a considerable amount of depth compared to other portions of the stream. As such, I rely on slow sinking lines such as a full sinking intermediate or hover line. At times, six to eight feet of T-8 or T-11 can come in handy. Retrieval speeds are generally slow to moderate and produce the best results, regardless of the line you employ. The length of my line strips are generally in the one and a half to two foot range. Speeding up the retrieve and shortening the stripping lengths is something I generally do only when my standard approach is not producing.

While streamers are a go-to choice, even better results come from aquatic invertebrate imitations. Much of what exists in the lake is also available to trout on the Snake tailwater reach. Damsel nymphs, dragonfly nymphs, and daphni get washed out of the lake with increased releases. I have caught lake trout, cutthroats, and brown trout with all of these types of forage lodged in their throats as I removed hooks. Chironomid larva and pupa imitations are also good choices. My favorites include simple patterns like Zebra Midges and more intricate flies like Day-2 Midge Pupa. These bugs are not just about winter. They will work all year long.

More stream-oriented bugs like gray drakes, callibaetis, caddis, PMDs, yellow sallies, and Alloperla golden stones populate this part of the Snake. Grey drakes and callibaetis tend to emerge in early summer (June into early July). I will perform slow pinch or figure-8 retrieves to imitate the movement of these swimming nymphs in eddies and seams. Caddis, yellow sallies, golden stones, and PMDs will emerge in late June through July and can be counted on well into August. Double nymph rigs imitating one or more of these bugs are killer in the same water where drakes produce. Caddis and PMDs imitations can also be go-to patterns in the slow, shallow riffles found below the dam. Tricos are late summer emergers on this part of the Snake River. #18 to #20 nymph imitations can be deadly when lake trout and other species are keying in on them.

It is important to understand that Jackson Lake is a natural lake. The Bureau of Reclamation built the dam in the early 1900s. It is only 65 feet in height and stores water only down to the 40 foot level of the water column. You will not be dealing with the down-right frigid temperatures found spilling out of reservoirs feeding other tailwaters like Utah’s Green River or the San Juan below Navajo Dam in New Mexico (both over 400 feet tall). Early season water temperatures can be in the high 30s. Summer temperatures, however, are typically in the mid-50s. I have measured the temp at 64 degree in early August of 2018. Keep this in mind when throwing on your waders. With air temperatures often over 80 degrees and the intensity of the sun when fishing at 6,800 feet of elevation, you might be getting out of those waders pretty fast.

Native vs. Invader and the Survivability Factor

I have had the opportunity to fish throughout the world for everything from taimen in Mongolia to golden dorado in Argentina to permit in Mexico and Belize. At the same time, I was raised around native cutthroat and they remain unquestionably my favorite fish. My love and concern for them has been documented numerous times in my writings and film work. Despite this, I often get looks of shock by fellow fly fishers when I discuss with admiration the possibilities of hooking into a large mackinaw on the Snake River.

“How can a native trout lover want to target an invasive killer like lake trout?” That seems to be the thought going through their heads.

Yes, lake trout have wreaked havoc on stillwater where cutthroats once dominated the scene. The concerted efforts of the National Park Service, Trout Unlimited, and the fly fishing public are fortunately turning the tide on the lake trout population illegally introduced to Yellowstone Lake, perhaps the greatest native trout fishery in the lower 48. Other waters have not been so lucky. Jackson Lake itself was a thriving cutthroat fishery a century ago. Today, I can go an entire season without catching one unless I spend substantial time casting to tributary inlets. It is managed as a lake trout fishery today for precisely this reason.

But my advocacy for native trout is not a zero-sum position. The formerly fishless Firehole River is now a treasured fly fishing stream offering shots at rainbows and brown trout. Other water, such as most of the Henry’s Fork in Idaho or the Madison in Montana, have not held native cutthroat since the 1890s. Nonetheless, they are fabled trout streams where impressively large rainbows and brown trout dominate the scene. I will fight as much for these places as I will for viable native trout water.

There are also rivers where either a certain degree of compatibility exists between native and invasive fish or invasive just don’t survive long enough to do irreparable harm. Lake trout on the Snake below Jackson Lake Dam is an example of the latter.

Like all fish, lake trout have evolved to survive in environments with specific requirements. They are not cut out for streams. The simple fact of the matter is that lakers on the Snake River do not live too long. WDGF lake trout specialist Diana Miller pegs the maximum duration of survival at around one year. This is readily evident to the angler. Recent arrivals tend to show a certain amount of health and plumpness. Those that have been in the river for several months will retain their length, but will be noticeably slender.

This is as good a reason as any to harvest lakers caught on the Snake. They just won’t last too long out there. And if a fly fisher is still concerned about these fish competing with the native cutthroat, that is a good reason to whack them, too.

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