below Mackay Reservoir
As of October 27, 2026, the Big Lost River is fishing Fair (7.8/10): Baetis activity, reported by 1 shop.
Last updated
Reports indicate fair conditions.
Conditions are holding steady since the previous update.
Cold tailwater below Mackay Reservoir. Large rainbows. Best late June through September.
A quick view of the latest report, gauge, hatch, and fly data available for this water. Missing observations are left unreported rather than estimated.
Current reports mention Baetis, Midge, Trico. Recommended flies include Blue Wing Olive, Zebra Midge, Streamers, Crane Flies.
Recent reports mention below Mackay Reservoir.
Access and seasonal rules can change. Check current regulations and closures with Idaho Fish and Game ↗
Reference location for this water. Individual reports and gauges may describe other locations; this is not a verified access point.
Big Lost River location
43.9392, -113.6483
Observations from the last 48 hours. Each measurement and chart describes its named station.
| Insect | Stage | Timing |
|---|---|---|
| Baetis | — | afternoon |
| Midge | — | afternoon |
| Trico | — | afternoon |
| Tricos | adult | morning |
| Crane Flies | adult | — |
| Crane Fly | adult | midday |
| Cranefly | adult | — |
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Locations come from the source report. A gauge reference does not establish where every fishing observation was made. Hatches and fly recommendations belong to their individual report.
Silver Creek Outfitters
Flows are dropping and currently around 195-196 CFS; Baetis, midges, and a few lingering Tricos expected during early to late afternoon. When surface activity slows, dry-dropper or Euro nymphing is most effective.
Reported location: below Mackay Reservoir
Hatches in this report: Baetis, Midge, Trico.
Silver Creek Outfitters
Flows are expected to drop as irrigation demands decrease, concentrating fish around buckets. There is a solid midday Baetis hatch along with lingering Tricos and fishing has been decent.
Reported location: Below Mackay Reservoir
Hatches in this report: Baetis, Trico.
Silver Creek Outfitters
Flows dropping as irrigation demands diminish; Baetis expected on the water in early afternoon as the day warms. Fish can be found eating dries in shallow seams and riffles; dry-dropper rigs are recommended.
Reported location: Below Mackay Reservoir
Reported water clarity: clear
Hatches in this report: Baetis.
Silver Creek Outfitters
Flows should drop as irrigation demands diminish; Baetis are appearing in early afternoon as temperatures warm. Fish can be found eating dries in shallow seams and riffles, and a dry dropper rig is recommended.
Reported location: below Mackay Reservoir
Hatches in this report: Baetis.
Silver Creek Outfitters
Flows have dropped to 260-268 CFS and conditions are ideal for wade fishing with Tricos and good Baetis numbers from midday into early afternoon. When bugs disappear, nymphing with small Baetis or midge patterns and streamers are effective.
Reported location: below Mackay Reservoir
Reported water clarity: clear
Hatches in this report: Tricos, Baetis.
Silver Creek Outfitters
Flows dropping (~284 CFS) as irrigation demand decreases; fish moving to find holding water but dry fly action expected to be fantastic once flows settle. Baetis and midge replacing Tricos as conditions cool.
Reported location: below Mackay Reservoir
Hatches in this report: Tricos, Baetis, Midge.
Silver Creek Outfitters
Flows are wadeable but pushy at around 300 cfs. Tricos and Baetis are hatching as the day warms, with giant crane flies effective on the surface; nymphing with small Baetis or midge patterns keeps fish coming in the slower afternoon.
Reported location: Below Mackay Reservoir
Hatches in this report: Tricos, Baetis, Crane Flies.
Silver Creek Outfitters
Flows at 300 CFS and dropping; Tricos and Baetis hatch as the day warms with giant crane flies skittered on the surface. Bug activity slows in the afternoon but nymphing remains productive with small Baetis or midge patterns.
Reported location: below Mackay Reservoir
Hatches in this report: Tricos, Baetis, Crane Fly.
Silver Creek Outfitters
Flows around 340 CFS make the river accessible for strong waders, with feeding trout found in riffles, buckets, and along shallow edges. Tricos and Baetis are active in the mid-morning; afternoon fishing slows but nymphing still produces.
Reported location: below Mackay Reservoir
Hatches in this report: Tricos, Baetis, Cranefly.
Silver Creek Outfitters
Flows are around 350 CFS (reported at 321 CFS) and falling. Morning Trico hatch is decent with some Baetis, but afternoon fishing can slow considerably once hatches are done; nymphing will still produce fish. Reservoir turnover may cause flows to go off-color temporarily.
Reported location: Below Mackay Reservoir
Reported water clarity: clear
Hatches in this report: Trico, Baetis.
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