When is lake trout (mackinaw) season in Montana?

Montana keeps lake trout (mackinaw) open to fishing year-round for the 2026 regulation year — there is no closed season, though the daily bag and size limits below still apply every day.

What is the Montana bag limit for lake trout (mackinaw)?

The Montana daily bag limit for lake trout (mackinaw) is District-based — Western Fishing District 20 / day (40 in possession); Central + Eastern 3 / day (Eastern 6 in possession). Flathead Lake 100 / day with only 1 over 36 in (all 30-36 in released — FWP/CSKT suppression). Fort Peck Reservoir 3 / day (Eastern). Yellowtail Reservoir 3 / day.. The possession limit is Western 40; Eastern 6; Flathead Lake 100. Some named waters set a different limit — check the water-body overrides above.

Do you need a license to fish for lake trout (mackinaw) in Montana?

Yes. Montana requires a valid fishing license to fish for lake trout (mackinaw), with the usual exemptions for young children, state free-fishing days, and some senior or disabled-veteran categories. A license is valid only in the state that issued it, so non-residents need a Montana license — compare resident and non-resident Montana fees on the state regulations page below.

Are there gear restrictions for lake trout (mackinaw) in Montana?

Yes. In Montana, lake trout (mackinaw) fishing carries these gear rules: Hook-and-line; trolling + deep-water jigging permitted; Flathead Lake Mack Days registration via CSKT for derby entry + payouts; Spearfishing permitted on listed waters during ice-fishing season; Conservation License + Fishing License required (AIS Prevention Pass required for anglers 16+): $8 res Conservation + $21 res season fishing + $2 res AIS / $10 NR Conservation + $100 NR season fishing + $7.50 NR AIS; Confirm current-year FWP + CSKT Flathead Lake Fishing Regulations for reach-specific exceptions + Mack Days dates.

Do specific Montana waters have different lake trout (mackinaw) rules?

Yes. 4 named Montana waters carry rules that override the statewide lake trout (mackinaw) regulation, including Flathead Lake, Fort Peck Reservoir, Bighorn Canyon NRA, and 1 more. See the named water-body overrides above for the exact rule on each.

2026 regulation year

Montana Lake trout (Mackinaw) 2026 — Season, Bag Limit, Size Rules

Salvelinus namaycush

Last updated June 8, 2026

Montana lake trout (Mackinaw) fishery is dominated by Flathead Lake (200 sq mi — country's largest natural freshwater lake west of the Mississippi River — Flathead + Lake Counties NW MT), where lake trout introduced in 1905 exploded after the 1980s Mysis shrimp introduction reshaped the food web and now sustain one of the West's largest inland Mackinaw populations. Because lake trout predation drove the collapse of Flathead's native bull trout (federally Threatened ESA) + westslope cutthroat, FWP and the Confederated Salish & Kootenai Tribes (CSKT) — who co-manage Flathead Lake, with the Tribes holding jurisdiction over the south half and FWP the north half — run an aggressive Mackinaw suppression program: a liberal 100 / day limit with only 1 fish over 36 in (all fish 30-36 in must be released), plus the twice-yearly CSKT Mack Days harvest derby (spring + fall) that pays anglers per lake trout and removes tens of thousands of fish annually. Beyond Flathead, lake trout inhabit the Western District lakes (Swan Lake + Lake McDonald in Glacier NP + listed waters at the 20 / day Western standard), Fort Peck Reservoir (245,000-acre Missouri main-stem reservoir — Eastern District 3 / day), and Yellowtail Reservoir / Bighorn Canyon NRA (MT/WY joint reciprocal compact). Lake trout (Salvelinus namaycush) are the largest North American char and the apex predator of cold, deep lakes — slow-growing and long-lived (30-40+ years), which is exactly why suppression of an introduced population is so difficult once established. Open year-round on most waters.

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Season

Open year-round Open year-round on most waters; Flathead Lake FWP/CSKT Mackinaw suppression (100 / day, release 30-36 in, 1 over 36 in) + spring + fall Mack Days harvest derby; district-based limits elsewhere (Western 20 / Central + Eastern 3 per day).

Bag & possession

Daily bag: District-based — Western Fishing District 20 / day (40 in possession); Central + Eastern 3 / day (Eastern 6 in possession). Flathead Lake 100 / day with only 1 over 36 in (all 30-36 in released — FWP/CSKT suppression). Fort Peck Reservoir 3 / day (Eastern). Yellowtail Reservoir 3 / day.
Possession: Western 40; Eastern 6; Flathead Lake 100

Size, slot, trophy rules

Size: Flathead Lake: release all 30-36 in, only 1 over 36 in; no minimum elsewhere
Slot: Flathead Lake protected slot 30-36 in (mandatory release) + only 1 fish over 36 in / day — structured to maximize removal of small + mid-size lake trout while limiting trophy harvest under the FWP/CSKT suppression program
Trophy rule: Flathead Lake holds one of the West's largest inland Mackinaw populations (introduced 1905, exploded after the 1980s Mysis shrimp introduction) — the twice-yearly CSKT Mack Days harvest derby (spring + fall) pays anglers per lake trout and removes tens of thousands annually to protect native bull trout + westslope cutthroat; trophy lake trout to 30+ lb hold over the deep structure; lake trout are the largest North American char, slow-growing + long-lived (30-40+ years)

Gear restrictions

Hook-and-line; trolling + deep-water jigging permitted; Flathead Lake Mack Days registration via CSKT for derby entry + payouts
Spearfishing permitted on listed waters during ice-fishing season
Conservation License + Fishing License required (AIS Prevention Pass required for anglers 16+): $8 res Conservation + $21 res season fishing + $2 res AIS / $10 NR Conservation + $100 NR season fishing + $7.50 NR AIS
Confirm current-year FWP + CSKT Flathead Lake Fishing Regulations for reach-specific exceptions + Mack Days dates

Named water-body overrides

Where statewide rules differ on specific Montana waters:

Flathead Lake
100 / day with only 1 over 36 in + all 30-36 in released (FWP/CSKT co-managed Mackinaw suppression — Tribes manage the south half, FWP the north half); spring + fall CSKT Mack Days harvest derby pays anglers per lake trout
Fort Peck Reservoir
3 / day + 6 in possession (Eastern District); lake trout alongside the walleye + sauger + chinook salmon + northern pike fishery
Yellowtail Reservoir + Bighorn Canyon NRA
3 / day (MT general limit outside Flathead Lake); MT/WY joint reciprocal compact on the boundary reservoir
Swan Lake + Western District lakes
20 / day (40 in possession) Western District standard; FWP suppression-aware management to protect native bull trout

Official source

Montana Fish, Wildlife & Parks (FWP) publishes the authoritative 2026 Montanafishing regulations. Always verify the current rule before fishing — emergency closures and in-season changes can override what's published here.

Visit official Montana fishing regulations →

Emergency-order channel

Lake trout (Mackinaw) closures, slot-limit changes, and harvest pauses are posted to Montana Fish, Wildlife & Parks's emergency-order feed — check it before any Montana trip during the active season.

Frequently asked questions

When is lake trout (mackinaw) season in Montana?: Montana keeps lake trout (mackinaw) open to fishing year-round for the 2026 regulation year — there is no closed season, though the daily bag and size limits below still apply every day.
What is the Montana bag limit for lake trout (mackinaw)?: The Montana daily bag limit for lake trout (mackinaw) is District-based — Western Fishing District 20 / day (40 in possession); Central + Eastern 3 / day (Eastern 6 in possession). Flathead Lake 100 / day with only 1 over 36 in (all 30-36 in released — FWP/CSKT suppression). Fort Peck Reservoir 3 / day (Eastern). Yellowtail Reservoir 3 / day.. The possession limit is Western 40; Eastern 6; Flathead Lake 100. Some named waters set a different limit — check the water-body overrides above.
What size lake trout (mackinaw) can you keep in Montana?: The Montana size rule for lake trout (mackinaw) is Flathead Lake: release all 30-36 in, only 1 over 36 in; no minimum elsewhere. Slot limit: Flathead Lake protected slot 30-36 in (mandatory release) + only 1 fish over 36 in / day — structured to maximize removal of small + mid-size lake trout while limiting trophy harvest under the FWP/CSKT suppression program. Trophy rule: Flathead Lake holds one of the West's largest inland Mackinaw populations (introduced 1905, exploded after the 1980s Mysis shrimp introduction) — the twice-yearly CSKT Mack Days harvest derby (spring + fall) pays anglers per lake trout and removes tens of thousands annually to protect native bull trout + westslope cutthroat; trophy lake trout to 30+ lb hold over the deep structure; lake trout are the largest North American char, slow-growing + long-lived (30-40+ years).
Do you need a license to fish for lake trout (mackinaw) in Montana?: Yes. Montana requires a valid fishing license to fish for lake trout (mackinaw), with the usual exemptions for young children, state free-fishing days, and some senior or disabled-veteran categories. A license is valid only in the state that issued it, so non-residents need a Montana license — compare resident and non-resident Montana fees on the state regulations page below.
Are there gear restrictions for lake trout (mackinaw) in Montana?: Yes. In Montana, lake trout (mackinaw) fishing carries these gear rules: Hook-and-line; trolling + deep-water jigging permitted; Flathead Lake Mack Days registration via CSKT for derby entry + payouts; Spearfishing permitted on listed waters during ice-fishing season; Conservation License + Fishing License required (AIS Prevention Pass required for anglers 16+): $8 res Conservation + $21 res season fishing + $2 res AIS / $10 NR Conservation + $100 NR season fishing + $7.50 NR AIS; Confirm current-year FWP + CSKT Flathead Lake Fishing Regulations for reach-specific exceptions + Mack Days dates.
Do specific Montana waters have different lake trout (mackinaw) rules?: Yes. 4 named Montana waters carry rules that override the statewide lake trout (mackinaw) regulation, including Flathead Lake, Fort Peck Reservoir, Bighorn Canyon NRA, and 1 more. See the named water-body overrides above for the exact rule on each.

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