Lake of A Million Big Trout - Bill Herzog

If you love to fly fish for large trout in lakes, put Henry’s Lake in Idaho on the must-do list this summer/fall.

henrys lake trout fishing park montana idaho snake river

Centennial Valley in southwest Montana is right out of any Western. Fifty miles long, meandering streams, sage and scrub trees, ten miles wide bracketed by mountains.

You would expect a stagecoach to come by most anytime. Time forgot about this valley, scenery to keep the mouth open long enough to get a sunburn on the tongue.

trout fishing wyoming montana idaho cutthroat rainbow

We weren’t here just for the scenery, the promise of westslope and Yellowstone cutthroat in the nearby lakes brought us here.

And they were there, pretty little tropical fish colored cutthroats 12 to 16”, good numbers and not educated enough to leave our flies and small dark jigs alone. To get here, you have to go up and over the Continental Divide on some sketchy dirt roads. And pass up a lake that, looking back, was really not a smart thing to do, regardless of the beauty and fishing opportunity of the valley.

The lake JD Love and I drove right past was Henrys Lake, not in Montana at all but in a seemingly borrowed horseshoe of land that Idaho gripped from Montana years ago.

JD guided on Henrys Lake decades ago, and as we went right along its shoreline, he told me about the insane numbers of pure strain Yellowstone cutthroat, eastern brook and Kamloops rainbow/Yellowstone hybrids that reach holy s**t sizes and how ridiculous the fishing can be numbers wise for outsized trout.


It was early June, the lake had just opened and by the number of pontoon boats, cartoppers and any type of trailerable floating craft the fishing must be happening.

Although every type of gear is legal here (bait, barbs) most of the travelling anglers are here for the open division class fly fishing. Everyone wants a chance at a 6-pound-plus trout on a fly, and this place is ground zero for that opportunity. While being a very skilled caster and knowledgeable lake fly angler certainly helps, one of the big draws to Henrys Lake is you don’t have to be super talented to catch a trophy trout.


The Lake

The instant you leave Montana on Highway 87, when you crest the hill and see the “Welcome to Idaho” sign, you see Henrys Lake, right on the tip of eastern Idaho. Henrys sits in an ancient volcano at 6,472 feet in the Caribou-Targhee National Forest in Freemont County. The Centennial Mountains rise up on its southern side with Henrys Lake Mountains along the west. I just don’t have a deep enough thesaurus to pile on the giddy feels of these mountains. At almost 5 miles long and 3-1/2 miles wide, this mountain lake sitting in this huge bowl is the home to out of nowhere strong winds that can pop up any time and make fishing a dicey activity. Keep a close eye on the weather.

Wildlife is popping everywhere here. There are moose, elk, countless deer, pronghorn and yes, grizzlies. Don’t eat a honey and peanut butter sandwich and walk alone on the trails.

The lake is shallow, with an average depth of 15 feet (I believe the deepest places are no more than 25 feet) and features massive weed beds. But due to these characteristics, this lake is a food factory which means trout grow fast…and big.

Henrys Lake is the headwaters of the great Snake River. When I’m swinging flies for summer steelhead in November, I’m fishing parts of Henrys Lake.

The Fish 

Besides the average size of the trout, biologists figure there are 1.2 million (not a typo) catchable trout in Henrys Lake. “Catchable” here is anything from 15 inches on up, with the majority of them 14 to 18 inches.

Great trout if they got no larger, but there are so many from 18 to 24 inches and 3 to 6 pounds you need more finger and toes to count. A ten-pound trout gets no special notice here, just a squinty-eyed smile and nod.

Because of the biomass of insects, this lake is a nutrient rich factory that can handle large populations of trout and not worry about over population stunting and such. Idaho plants the lake with three types of trout—Yellowstone cutthroat, sterile eastern brook and hybrid rainbow/cutthroat. Ten percent are hybrid rainbow/cutthroat (190,000 planted yearly), 80% are Yellowstone cutts (just over a million!) and 10% (100,000 yearly) are brook trout.

trout rainbow cutthroat fishing brook

The hybrids grow the largest and fight the hardest. Ten to 15-pound hybrid trout are caught all through the season in Henrys. Eighteen inches to six pounds are the norm size for hybrids, but the chance for a real sockdolager is real anytime.

The sterile brook trout here grow fast and huge, they are some of the biggest brookies in the States. The Idaho stare record is a Henrys Lake fish of 7.2 pounds! The larger brook trout are the hardest to land here, as they typically bore like a Chinook into the rope-like weeds and break off.

The Yellowstone cutthroat are the main attraction here, with 17 to 23” fish common and 6 pounders are just a yawn and release…I could not land one during my stay (I hooked them…&$#@!!), a dozen or so 18 to 22 inches was the best I could muster but my partner JD got half a dozen 5 to 7 pounds on a slowly stripped #10 Renegade.

You may keep trout here, but the lake is managed as a trophy fishery with catch and release highly recommended.

In the spring, right after ice out and opener (May 16th) most trout are near shorelines in six to 15 feet of water. Weeds have not grown to full capacity yet and there are countless areas to fish. I would name the most popular areas but that is the one thing for the reader to figure out…there has to be some discovery on your part. Not to worry, first timers will figure out the program quickly.

As summer warms the water, trout will begin to gather in areas of cold-water springs, actual “holes” in the weeds where cooler water (with more feed) burbles up from the lake bed. This is when those million plus trout pile up in these cooler areas, which as you can probably imagine creates incredible opportunities for ridiculous number days. The locals call this time “pod fishing.” Even with the large number of anglers and fish caught every year, they estimate that only 10 percent of the trout in Henrys are ever caught.

bill herzog trout fishing fish

In the fall, the brook trout are staging a false spawn near creek mouths. Now is when the giant brookies are mostly caught, so if you want just a trophy brook trout your time is October at Henrys Lake. 


As much as I love to toss small 1/8-ounce spoons, Rooster Tails and small dark jigs for trout, fly fishing rules here and quite frankly fly fishing out produces gear most days.

I saw this firsthand; I brought my eastern Washington Box O’Death, also known as an assortment of 1/8- and ¼- ounce marabou/bunny dark flavored jigs. I caught exactly one trout in three days of throwing/twitching these “can’t-miss-automatic-just-add-water-trout killers.” And the box of hide-behind-the-bushes-so-I-don’t-get-mauled-by-giant trout Rooster Tails were similarly ignored. Head scratcher…definitely. This is because of the biomass of bugs and crawly creatures these trout are keyed into. Lures…meh. Because of the insect buffet, these trout feed 90 percent of the time subsurface. Fly fishing it is, when in Rome, as they say. So, when loading the fly gear for a trip to Henrys, leave dry flies in the garage.

fishing trout fly henrys lake

For Henrys Lake, 5- and 6-weight single-handed fly rods are standard issue. You will need two types of lines, on full floater for fishing indicators and one full sink, a Type 3 (sinks 3 to 4 inches per second) for stripping leeches and their ilk. A faster full sink like a type 6 quite frankly sinks too quickly in the weedy shallows and does not allow you to slowly work flies. Slow trolling leeches works great, but once mid-summer gets here and the trout gather in certain areas (or just for those who like to cast and work your flies) bring an anchor.

Leeches and tiny fish make up approximately 50% of the diet of trout over 16 inches.

So, we can safely say that slowly stripping 2- to 3-inch leech streamer patterns are the out of the truck go to’s. Find leech patterns in this order of colors: brown, dull red and black in #6, #8 and #10. Patterns like the Renegade or scuds also strip fish well. Of course, Woolly Bugger type streamers take a lot of trout here, think brown, red/black, black or olive. My best two patterns during our stay was a Henrys Lake Renegade and brown Seal Bugger Leech, both in size #10. While stripping, trout are not nearly as leader shy as when vertically presenting so 8-pound fluorocarbon tippet or 6-pound Maxima Ultragreen works fine and can take a swift grab from a 10-pound trout.

fly fishing trout henrys lake

Since Henrys is a shallow lake, most areas you will be fishing will be 10 to 20 feet deep, remember that weeds are your constant companion and carpet 95% of the bottom. Trout here cruise right on the top of the weeds, well, because that’s where the food is. After casting your full sinking line, begin a countdown before retrieval. After watching locals and lake veterans, I start at ten seconds, then 15 and so forth until I hit weed lines and go from there. The idea is to present your leech patterns horizontally immediately above the weeds.

Sink tips won’t do this properly. After your countdown six- to eight-inch strips every second is a good start. Sometimes they want it faster, sometimes slower, every day is different. Watch the successful guys around you, mimic their cadence. A great tip is to shove the first foot or so of your fly rod into the water while retrieving. This allows the line and fly to sink quicker, keeps it down and fishing horizontally and prevents the line from jumping back and forth near the rod tip. This allows more contact and immediate movement of flies.

When streamers won’t get bit (rare), break out a full floating line, put on a bobber and a chronomid. I am a “tight liner” a name given to those fly guys who would rather swing or strip a fly than put on a bobber. I would rather put my privates on a nuclear-powered belt sander than stare at a bobber, but there is no denying its effectiveness. The idea is to fix the bobber on the leader, so it presents the fly immediately above the weed line. Trout have all the time they need to examine your fly as it hangs there so a lighter, more invisible tippet is mandatory. Four-pound Maxima Ultragreen or a high quality 6-pound fluorocarbon does the gig for bobber fishing.

When you have adequately shut off your brain for bobber fishing, patterns for such slack jawed activities are something in red, black or dark green body in sizes 12 and 14 being most popular and effective. Same sized green or brown scuds are also a fine choice, even small #12 balanced leeches in brown, dull red or black.

Flat calm water is not ideal for indicator fishing, a slight 1- or 2-inch chop is money as it gives the fly a seductive slight wiggle. It’s usually “heave it and leave it” when the chop is on the lake. When flat calm (rare at Henrys) try the “strip and sit,” a very slow strip then a few second hesitation moves the fly ever so slightly like a disoriented bug.

trout fishing henrys lake montana snake idaho river

You will not be alone at Henrys Lake. It is a destination trophy trout fishery, expect boats all over the lake all day long. There is a great camaraderie here, however, and no one crowds anyone. Stay a long cast plus from the next boat and you will be fine. A good rule of thumb (Thumb? Who the hell came up with that saying?) is as the morning progresses and the trout in shallower water get hammered, move a bit away from all the pressure and go to slightly deeper water where you may find willing less tortured fish.

JD told me while we were there to look for pelicans. The big white birds are a staple feature at Henrys. He said that 30 years a go the lake pimps told him to look for the pelicans, that is where the trout are gathered.

Need flies or just some local knowledge, even a guide? A stop into one of the several bad ass fly shops in Ennis will hook you up proper. The best place I found was the Drift Lodge and Fly Shop on Highway 20 immediately south of Henrys. Their fly assortment will set you up for success and they have nice little rental cabins. If you can find a copy of the old book “Fishing Henrys Lake” by Bill Scheiss it’s definitely worth the read and to keep in the boat on your visit. There is camping and boat launching at Henrys Lake State Park on the south end and Frome County Park on the north end.

trout fly fishing fish catch tying

Henrys Lake sits right in the middle of Trout Nirvana. Highway 287 all the way in (and out) follows the Madison River. Hegben Lake and Island Park Reservoir are just a nine-iron away to the south and east, both have large rainbow and brown trout. Highway 20 from the lake is only 15 miles from West Yellowstone, so if the family is along your vacation is tailor made right there. Get your Idaho and Montana licenses and give a wave, squinty eyed smile and a nod as you go by.

- written by Bill Herzog


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