Big Lost River
Fly fishing the Big Lost River in Idaho, a freestone near Mackay and Sun Valley with rainbow, cutthroat and brook trout.
- 191 miRiver length
- 4Game fish
- 32Access points
In the FlyFishFinder appAbout the Big Lost
The Big Lost River drains the mountains near Sun Valley and flows past Chilly, Mackay and Arco through the high desert. It is a freestone river with scenery to match. Access is good and trout numbers are healthy at the main access points.
The fish are rainbow trout, brook trout, cutthroat trout and mountain whitefish. The tailwater below Mackay Dam has clear water and educated rainbows. Upstream and in the tributaries, fishing feels more like true backcountry freestone water.
Flows can change a lot. High water makes wading unsafe, so check a gage before you go. Warm Springs Creek, East Fork Wood River and the North Fork Big Lost are good nearby streams.
Pale morning duns, trico spinners and midges are the main hatches. Copper Johns work well as a nymph.
Check the current Idaho regulations. Some sections have their own rules.
Big Lost River below Moore Diversion near Moore, ID
Is the Big Lost fishing today?
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Nearby gages
- Antelope Creek near Darlington, ID6.4 mi away Not reporting USGS 13131000
- Warm Springs Creek below Diversion near Mackay, ID24.3 mi away Not reporting USGS 13124265
- Thousand Springs Creek near Chilly, ID29.5 mi away Not reporting USGS 13122000
- North Fork Big Lost River at Wild Horse near Chilly, ID37.0 mi away Not reporting USGS 13120000
- Little Wood River above High Five Creek near Carey, ID38.2 mi away Not reporting USGS 13147900
- Little Wood River near Carey, ID40.2 mi away Not reporting USGS 13148500
- Trail Creek near Sun Valley, ID46.1 mi away Not reporting USGS 13137300
- Silver Creek at Sportsman Access near Picabo, ID47.3 mi away Not reporting USGS 13150430
No gages that close. Try a wider radius.
See every gage on the map and today's top 10 rivers in the free appData from the U.S. Geological Survey. Recent readings are provisional and may be revised.
Fish you'll catch
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Hatching in November
What's on the water in the Upper Snake watershed this month, and the fly to match.
All 11 hatches this year
Light bars show the season and dark bars the peak. The ringed month is this month.
Tips for fishing the Big Lost
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Check flows first
Dam releases and runoff swing a lot. Do not wade if the river is high.
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Fish the tailwater with a light touch
The water is clear and the fish are wary. Make careful presentations.
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Carry Copper Johns and spinners
Copper Johns, PMDs and Trico spinners are local favorites.
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Explore tributaries
The smaller creeks hold brook trout and cutthroat in beautiful country.
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Drive carefully
Some access roads close in winter. Confirm routes before you go.
Every access point on the Big Lost, in your pocket.
- 32 mapped access points, with parking and put-ins
- Today's Fishability score, so you fish the day that lines up
- 7-day flow and water-temp trends for every gauge on the river
Rivers near the Big Lost
Big Lost River FAQ
What is the best time to fly fish the Big Lost River in Idaho?
The river stays open all year, but summer after runoff has the easiest access.
Where can I fly fish the Big Lost River?
The tailwater below Mackay Dam is the best known water. The app map shows mapped access points and gages along the river.
Can you wade the Big Lost River?
Yes at lower flows. High flows make it unsafe.
What flies work on the Big Lost River?
Copper Johns, PMD patterns and Trico spinners are local favorites. The FlyFishFinder app shows what is hatching and working on the Big Lost River today.
What fish are in the Big Lost River?
Rainbow trout, brook trout, cutthroat trout and mountain whitefish.
Are there special rules on the Big Lost River?
Some sections have special rules. Check current Idaho regulations before you fish.
