Thursday, September 16, 2021

Yellowstone’s Fall Lake-Run Brown Trout
Timing this run offers the best shot at a giant brown trout.
By Boots Allen

Many contend Rocky Mountain brown trout initiate their spawning migration from lakes on the first full moon after the fall equinox. Some streams experience runs well before this event.

Autumn is a special time in the West. Summertime crowds dissipate, air temperatures are crisp, foliage display rich hues, and wildlife is robust and easily visible as animals initiate their fall migrations and rutting activities.

For fly fishers, autumn brings another bonus—the fall spawning run made by brown trout on rivers throughout the Rocky Mountain region. While stream-resident brown trout runs are super popular in the angling community, I’m personally more intrigued by the lake-runs. These are the fish that pour out of stillwater environments and into scores of streams with the sole intent of passing on their genes to another generation.

Many anglers assume that all brown trout spawning runs are the same—they start in the fall, run upstream, spawn, and then disperse in the winter. The truth is, they are quite diverse, with differences in timing, tempo, and system-specific attributes. It’s a complex puzzle to figure out. Even after 30-plus years of fishing them I find myself perplexed at times.

I live in the Greater Yellowstone area where three lakes—Hebgen in Montana, Lewis in Yellowstone National Park, and Jackson Lake in Wyoming—experience brown runs as different as western swing dancing is from ballet. I try and fish each at least once year.

Hebgen Lake
Hebgen Lake browns migrate up the Madison River in autumn to spawn. Their run goes well into Yellowstone National Park. Fly fishers have been targeting them for several decades. It’s a well-known event in most trout fishing circles. If you have issues with mobility, this portion of the Madison might not be for you. If you love wade fishing, it’s damn close to nirvana.

What initiates a spawning run, be it on the Madison or any other stream, is widely debated. Some contend changes in photo light (the shortening of daylight hours and where the sun sets on the horizon in fall) is a major factor. Others believe moon phase is the driving force. Still others suggest it’s a combination of the two.

A common argument by those placing weight on lunar influence contend brown trout begin their spawning run on the first full moon after fall equinox. Yet on the Madison, this is clearly not the case. West Yellowstone legend Bob Jacklin has seen Hebgen Lake brown trout at Bakers Hole (a few miles upstream of Hebgen Lake) just after Labor Day. My experience matches Jacklin’s. One of my most productive days fishing for Hebgen browns came inside Yellowstone National Park on fall equinox in 2004. I was no fewer than 15 river miles upstream of the lake.
The beauty of the Madison River run is its duration. Most years it seems like a constant surge of fish from September through October.According to some locals, there are still fish coming upstream in November.

Most fall brown trout are taken by wading anglers, but a boat does offer some advantages, especially when probing the mouths of streams.

Lewis Lake
Located in the northwest quadrant of Yellowstone National Park, historically fishless Lewis Lake was stocked with Loch Leven brown trout in 1890s. They have flourished since that introduction.

While Hebgen Lake browns appear to begin their run as early as the first week of September, Lewis Lake fish seem to be more in line with the equinox claim. These fish are a true October phenomenon. I generally observe them staging at the mouth of the Lewis River as early as the last week of September and as late as the first week of October before making their push upstream. The fishing remains strong through October and up until fishing closes in early November.

Some stream inlets, like the Lewis River, have slow currents, allowing anglers to row well upstream to stalk lake-run browns.

The Lewis Lake run differs from Hebgen not only in timing, but in how you fish it. The river upstream of the lake is less than four miles long (where it connects with Shoshone Lake). That entire length is referred to as the Lewis River Channel. The upstream half is shallow with a moderate gradient. Almost all the spawning occurs here. Like so much of the upper Madison, fishing here is wading intensive. The lower reach of the channel is wide, deep, slow, and difficult to fish without watercraft. This is where I spend most of my time when fishing the run. Browns tend to move upstream in several pods and are easily seen. A finely placed cast with the right streamer can entice several chases and often an aggressive eat, once you find the fish.

Lewis is a natural lake with no impoundment. This gives brown trout the ability to move downstream and spawn in the river below the lake. It is the only run I fish regularly with such a characteristic.Browns moving downstream are fewer in number and start their run later in October. The weather can be crummy and the fish less abundant, but the results are worth it if you hit it right.

The meat of Jackson Lake’s brown trout run occurs from late October well into November.

Jackson Lake
The spawning behavior of Jackson Lake brown trout flies in the face of most stereotypical views. These fish move up the Snake River and deep into Yellowstone National Park. It happens much later than other spawning runs. While I have seen Jackson Lake browns a good dozen miles upstream as early as the third week of October, the meat of the run occurs more towards the end of the month and then into November most years.

This migration is an odd one and exceedingly difficult to time properly. Jackson Lake does not contain an overly plentiful population of browns (low thousands as opposed to tens of thousands). This produces a run measured in a couple of weeks, where as Hebgen and Lewis Lake runs are elongated and may last for a month or more. It is an aggravatingly quick surge of fish. If you wait too long and your timing is off, you could easily miss it and find fish that are already on their spawning beds. If you hit it right, however, it’s hard to find a more adrenaline producing event.

Jackson Lake brown trout behavior is also unusual in that not all are main-stem spawners.A good number of fish run up small creeks only a few miles from the inlet where they find picture-perfect spawning gravel. Focusing solely on the main river and too far upstream neglects the action you can find on smaller, more intimate waters further downstream.

A moral dilemma?
Fishing for migrating brown trout probably started shortly after the first fish were brought here from Europe over a century ago. And for just as long, people have questioned the act. Some claim that these hormonally charged fish are an easy target. Others contend they are fragile creatures performing energy draining acts. Hooking into them just drains their energy reserves.

At the same time, most of us are not fishing for brown trout in the act of spawning. We target them during the migration. It is no different than when we fish for steelhead and salmon. Almost all of these fish are being released back into cold, oxygen rich water where they can recuperate and resume their run upstream. We are treating them with extreme care for the most part, and no less so than any other fish we target or at any other time of their lifecycle.

Boots Allen
Boots Allen is a fly fishing guide and writer who lives with his wife and two kids in Victor, Idaho. His latest book is Finding Trout in All Conditions.