The upper river, for example, meanders through the remnant part of
the Park above the lake, far from any road. The source itself lies
outside the Park, tucked away even more remotely inside the
Bridger-Teton Wilderness of Wyoming. You can get to the upper
river by boat up the lake, by horseback, or by a long backpack
trip. But you'll never see it if you have to drive to it.
The canyons, both the Grand and Black, are difficult to get into,
more difficult to move along. Most access is at points along
trails, where you can fish a few pools or runs, then have to climb
back up, hike to the next access point, descent to fish again.
Atlantic Creek, Yellowstone Headwaters
Most trout in the upper river, and its tributaries like
Thorofare, are not resident. They live on the lake [Yellowstone Lake]
and move up to spawn as soon as the water begins to drop after
snowmelt torrents tear through. At this elevation - nearly 8,000
feet- spring comes late. Runoff typically last until early
July. Trout finish spawning and back down from the tributaries
soon after that. They hang out for weeks in the bemeadowed upper
river, furnish it with fish out of proportion to its meager carrying
These lake fish are far larger than you would expect from the size
of the stream. They average sixteen inches. The largest weighed
over three pounds. [These spawning fish are cutthroat]. . .
Heed a couple of cautions about the upper river. First, the
silty bottom can get stirred up by a storm. It also comes back
into shape quickly. If you go there, give yourself a few fishing days
so you'll be sure to have some time when the water is clear. Second,
mosquitoes are fierce in the marsh that is the old lakebed. We
went to the area in late August, after the sun had a chance to
bake the meadows dry. In July, when you can first fish the river,
they might carry off your camp.
The best timing for a trip into the upper river has to hit a fairly
narrow window: after the runoff ends in July, before the trout
back down in September. I would advise the last two weeks of
August. You'll see slightly fewer fish, but still catch plenty.
You won't get devoured by mosquitoes. In September the weather
becomes risky [snow], and the numbers of trout dwindle.