Idaho runs one of the most generous general trout limits in the West — six trout a day on most water — and then layers strict, river-specific exceptions on top of its best fisheries. The general rule is the easy part. The exceptions are where anglers get tickets.
Licenses and Permits
Everyone 14 and older needs an Idaho Department of Fish & Game (IDFG) fishing license. Kids under 14 fish free with a licensed adult. Idaho sells resident annual, non-resident annual, and short-term licenses (1-day and 3-day with consecutive add-on days), which is the cheap way in if you're driving over from Oregon or Utah for a long weekend.
Two add-on permits matter for fly anglers chasing anadromous fish: a steelhead permit for the Clearwater, Salmon, and Snake, and a separate salmon permit for chinook seasons. Both are sold on top of the base license.
No fixed dates here: Idaho sets season dates, bag limits, and emergency closures year to year. Always confirm current rules at idfg.idaho.gov before a trip — steelhead and salmon seasons in particular open and close on short notice.
The General Trout Rule — and Its Limits
Statewide, the general limit is six trout, all species combined, with no minimum length and few gear restrictions. That covers a huge amount of backcountry and stocked water. But every premier river on this site is managed under a special regulation that overrides the general rule — read the section notes in the IDFG rule book for the exact stretch you're standing in.
Species Rules That Trip People Up
Bull trout — release, always
threatened — ESA listed
Bull trout are a federally threatened char, not a trout, and are catch-and-release statewide on nearly all water. If you hook one in the Lochsa, Selway, or upper Clearwater drainage, photograph it in the net and let it go. A few lakes allow limited harvest under permit — those are the rare exception, not the rule.
Westslope cutthroat — wild fish go back
native, zero-harvest in many drainages
Across the Panhandle and Clearwater region — the St. Joe, Lochsa, and Selway — wild cutthroat are managed catch-and-release with a zero bag. These are native fish in native water, and the regs reflect it. Treat all cutthroat in those drainages as no-kill unless the rule book says otherwise.
Steelhead and salmon — hatchery only
adipose clip = legal to keep
On the Clearwater and Snake, only hatchery steelhead — identified by a clipped adipose fin — may be kept. Any fish with an intact adipose fin is wild and must be released unharmed, in the water. Chinook seasons run the same way and are set by emergency order based on run counts over the dams.
The No-Kill and Quality Waters
Two of Idaho's signature trout fisheries are flat-out no-kill on their marquee stretches:
The Henry's Fork through Harriman State Park (the Railroad Ranch) is catch-and-release, artificial flies only — the spring-creek flat water that built the river's reputation. The South Fork Boise below Anderson Ranch Dam runs a restrictive trophy regulation through the canyon: artificial flies and lures only, with a low bag and a high minimum length that effectively makes it a release fishery for all but the largest fish.
The Big Lost River below Mackay Dam carries its own quality-water rules, and the St. Joe layers stricter limits as you move upstream into the cutthroat water. None of these match the general six-fish rule — check the specific reach.
Fish it: On any catch-and-release water, pinch your barbs before you rig up. It's required on most no-kill stretches and it speeds every release whether the rule demands it or not.
Tribal Co-Managed Waters
The lower Clearwater and Snake are co-managed with the Nez Perce Tribe, whose treaty fisheries run alongside the state-regulated sport season. Non-tribal anglers follow IDFG rules and tribal members fish under tribal regulations, but you'll share ramps, runs, and harvest data on the same water. Up on the eastern Snake, the Shoshone-Bannock Tribes manage the Fort Hall reservation waters separately — you need their permit, not a state license, to fish there.
The Takeaway
Buy the base license, add the steelhead or salmon permit if you're after anadromous fish, and then assume every named river on this site has a special regulation that beats the general six-trout rule. Release all bull trout, release wild cutthroat in the Clearwater drainages, release any steelhead with an intact adipose, and pull up the current IDFG rule book for the exact stretch the day before you go.
Check conditions before your next trip.