Weird Fisheries #1: Swan Lake Flat Sloughs

Weird Fisheries #1: Swan Lake Flat Sloughs

This is part 1 of a series of posts I’ll make through the season about “oddball” fisheries. I’m not going to reveal any hidden gems or tell you which rock to stand on, but I do intend to mention some fisheries “in the margins,” that might be fun for some PFS customers for an hour or two. Some of these fisheries will be in the park. Some will be quite far abroad in Montana. Enjoy!

Swan Lake Flat Sloughs

The marsh through which Swan Lake drains into Glen Creek is located east of the Mammoth-Norris Road immediately south of Rustic Falls. This fishery is swampy, difficult to get around in due to sucking mud and sudden deep holes, provides perfect habitat for mosquitoes though not for trout, and is often crowded with hikers and bikers using the dirt Bunsen Peak Loop Road, one of the few trails in Yellowstone Park where bikes are permitted.

So why fish here? That’s simple: it’s one of only two options near Mammoth where trout can always be caught during the first week or two of the Yellowstone Park season (the other is Joffee Lake). I’ve had clients catch fish here in the last few days of May while standing on snowbanks.

The Swan Lake Flat sloughs begin at Swan Lake’s outlet. During the peak snowmelt from mid-May through mid-June, the lake drains via a seasonal stream from its northwest end. This outflow passes under the road in a culvert, then arcs in a crescent first northeast, then northwest to join Glen Creek adjacent to the Bunsen Peak Trailhead immediately south of Rustic Falls (on Glen Creek). This marshy outflow forms ponds (almost all associated with spring seeps) connected by narrow, deep channels. In late summer and fall, the meadow adjacent to these channels is dry, but in early June the entire area is a marsh filled with ankle- to thigh-deep water and sucking mud.

Because the fish in this series of ponds and channels come from Glen Creek, the lower holes typically have larger fish numbers. That said, after a couple good water years when the ponds don’t get too warm and the marsh doesn’t dry up, fishable numbers of small to moderate-sized brook trout can be found almost all the way to Swan Lake. The areas where higher ground gets closest to the larger pools offer easier access. The larger holes, which usually host beavers and muskrats, require a long slog through deep water, grass, and mud.

I guide here once or twice almost every year, always before the middle of June when there are few other options. This is not a numbers fishery, but it is a fishery, and places to fish are hard to come by in the northern part of Yellowstone Park in early June.

Because this is flat, clear water, the brook trout here (which run five to twelve inches) are spooky. When guiding beginners, I usually have them fish a midge pupa and a soft hackle under a tiny indicator, without additional weight, then have them cast these rigs out along the deeper weed lines. Every fifteen or thirty seconds, I have them give their lines a slight twitch. This isn’t quite worm and bobber fishing, but it’s close. This is about the only way beginners will succeed here, since otherwise they can’t reach out far enough to avoid slapping the water and spooking the fish.

When guiding more experienced clients, I have them use similar flies most of the time, but will have them either look for the occasional rise to cover or cast as far as they can and retrieve their flies with a slow hand twist retrieve. Brook trout streamers like the Joffee Jewel or traditional Mickey Finn can also work with this tactic, especially right at the start of the season, before any insects are active. When the bugs are active, usually midges (and mosquitoes), a tiny Adams Parachute or #16 Coachman Trude with an even smaller midge pupa under it will draw some rises.

All in all, this water is a good diversion for a couple hours, if there’s no time to drive down to one of the Madison Drainage rivers that are also fishable at this time.

The easiest access and the only one that receives appreciable fishing pressure is the Bunsen Peak Trailhead just south of Rustic Falls. The northernmost pool is right next to the trailhead. Otherwise, use one of the pullouts further south towards Swan Lake itself and walk (slog) to the creek. Beware of critters: mosquitoes, bears, and calving elk. A cow elk once followed me all the way back to the car here, after I must have gotten too close to her calf. Also be careful slogging through the marsh, and avoid wearing clothes you don’t want to get dirty. Odds are you’ll wind up eating it if you squelch too far out.

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