Yellowstone at 740 cfs and Rising: Boat Ramp Closed, PFAS Advisory Issued

What's Biting

What's Next

**Flow Watch: 740 cfs and Likely Climbing**

The USGS gauge 06043500 reading of 740 cfs as of May 6 afternoon is the clearest on-the-ground signal available this week. In a typical year, Yellowstone watershed flows ramp sharply through mid-May as snowmelt accelerates out of the Absaroka and Beartooth ranges. If warming continues over the next few days, expect that number to climb—likely pushing clarity down in the main stem and concentrating trout along softer inside bends and bank edges where current slackens.

For anglers willing to adapt to off-color conditions: weighted stonefly and hare's-ear nymphs fished tight to the bank in 2–5 feet of water have historically produced during spring runoff push. Streamers quartered downstream on a slow, jig-like retrieve can pull brown trout out of undercut banks when the main channel runs turbid. The waning gibbous moon favors low-light feeding windows, so the first two hours of daylight and the hour before dark are your best timing targets on the main stem.

**Tailwater Sections Are Your Best Bet Through Mid-May**

When the main stem muddies, tailwater stretches fed by dam releases typically hold clearer, colder water and are worth prioritizing through at least mid-May. Hatch Magazine's coverage of caddis emergences in Yellowstone-region waters points to afternoon warm-ups—roughly 2–5 p.m.—as the prime window to watch for rising fish on these clearer runs. A caddis dry or soft-hackle wet fished in the film is the appropriate tool when the hatch fires; water temperature approaching the 50°F range is a reliable trigger to start watching the surface.

**Access Note: Plan Your Put-In Now**

The partial closure at Grey Bear Fishing Access Site is projected to run through approximately May 21, per MT FWP Fishing News. The boat ramp and main parking area remain restricted. Float anglers on the Yellowstone corridor should lock in alternative put-ins well ahead of weekend trips. MT FWP Fishing News notes that project updates are posted to regional Facebook pages and at myfwp.mt.gov/fwpPub/allRestrictions—check both before trailering your raft.

**PFAS Advisory: Know Before You Keep**

MT FWP Fishing News confirmed a joint agency release of PFAS fish consumption advisories covering some Montana waterbodies. Catch-and-release fishing is not restricted, but anglers who plan to keep fish for the table should review the advisory list directly through MT FWP before harvesting. No specific waters within this reporting region were named in the available bulletin—verify the full list with MT FWP prior to any trip where harvest is planned.

Context

Early May sits squarely in Montana's runoff transition window. The Yellowstone River typically sees its annual flow crest between late May and mid-June, so a reading of 740 cfs on May 6 suggests we're in the upswing but not yet at peak. That is, historically, the sweet spot for experienced anglers who know how to read off-color water: trout feed actively ahead of the season's most turbulent conditions, and a productive window of nymphing and streamer fishing often precedes the extended blow-out period that clears most wade anglers off the main stem entirely.

MT FWP Fishing News did not report species-specific bite conditions this week—the agency's recent communications have centered on the Grey Bear access closure, the upcoming 2027–2028 regulations public comment meeting in Billings on May 11, and the new PFAS advisory release. That means no state-agency catch data is available to ground-truth current fishing quality. Any species status listed in this report reflects historical seasonal patterns and gauge readings, not confirmed field reports. Anglers planning a trip should call a local shop or outfitter for real-time intel before making the drive.

On the Missouri River drainage, early May historically brings walleye and northern pike into more accessible post-spawn patterns as water temperatures climb toward the upper 40s and low 50s°F. Missouri tailwaters tend to run cooler and clearer than the main Yellowstone through this period, giving both fly and spin anglers more consistent windows even while Yellowstone tributaries run high and turbid.

Hatch Magazine's ongoing coverage of caddis emergences in Yellowstone-area waters aligns with what local fly fishing tradition has long recognized as one of the more reliable early-season hatch windows in the Northern Rockies—typically running from late April into June depending on elevation and annual snowpack. With no water temperature data available from gauge 06043500 this week, precise hatch timing remains uncertain, but the historical window is open now and worth prospecting on any clear-running stretch you can find.