Idaho Fishing Reports ยท Central Region
Below Mackay Dam, the Big Lost River is a productive tailwater with fat rainbows and some of the best numbers of trout in central Idaho.
Looking for the latest Big Lost River report? This page is updated by the AvidMax fly shop team with live flows, current conditions, hatches and the flies working now on the Big Lost River (below Mackay Dam).
Current flows
Wind forecast
Big Lost River fishing report
Updated November 7, 2026.
Fall flows are lower and clear.
Nymphs, small midges and streamers below the dam and down toward Mackay.
Load your fly box
Before you head to Below Mackay Dam, bring: Zebra Midge #18-22, Pheasant Tail Nymph #14-18, Woolly Bugger #6-8, Parachute Adams #16-20, Elk Hair Caddis #14-16, RS2 Emerger #18-22, JuJu Baetis #18-22, Black Beauty #20-24, Egg #14-16, Squirmy Wormie #12-14.
Flies working right now
The flies above that we have in stock right now.
Big Lost River details
| Access | Public access below Mackay Dam and along US-93 toward Mackay. |
|---|---|
| Elevation | About 5,900 ft |
| Nearest town | Mackay, Idaho |
| Best season | Year-round below the dam |
| Fish | Rainbow trout, some brook trout |
| Regulations | Check the Idaho Department of Fish and Game seasons and rules before you go. An Idaho fishing license is required for anglers 14 and older, plus a steelhead or salmon permit where those fish are targeted. |
| Leaders and tippet | 9 ft leaders, 4X to 5X tippet |
| Camping | Mackay Reservoir campground |
| Kids | Partly. |
| Good to know | Irrigation releases change flows. The lower river can go dry in summer below Mackay. |
Fishing by season
Winter
Midges below the dam.
Spring
BWOs and midges.
Summer
Caddis and PMDs.
Fall
BWOs.
How to get there
From Arco, take US-93 north to Mackay.