Upper Seymour Lake Depth Map & Fishing Spots (MT)

Hatch outlook

Grasshoppers (east-side summer)Active window

Typical here: Jul 1 – Oct 15 · until the hard frosts of mid-October; on the Missouri, August hoppers fish mid-river, not the banks

adultall day in high summer, best when afternoon wind knocks bugs onto the water

Pulls fish to the windward grassy banks and edges for months — fish the bank the wind blows ONTO.

The friendliest crossover of the summer: on lakes, drift the windward bank with a bubble-and-foam-hopper — the bubble's splash doesn't hurt a hopper presentation. On rivers, the same rig dead-drifted along the undercut grass banks, or small gold spinners under the banks between rises.

The event happens over grassy banks, undercut edges and windward shorelines

Spruce MothActive window

Typical here: Jul 20 – Aug 31 · a conifer-forest event — it needs fir and lodgepole on the banks, so it's a Rock Creek / Blackfoot / upper Bitterroot specialty

adultmorning through midday — moths don't enter the water willingly — landings are sporadic and near the conifer banks; fish the imitation LOW in the film with minimal floatant, even fully drowned, with a little movement

When the moths show, just about every run produces — large trout key on them so hard that one pattern carries the whole box for two weeks.

Honest limit: a small drowned-surface moth has no lure analog. The workable rig is a casting bubble with a drowned moth pattern along the timbered banks in the morning; otherwise fish spinners early and late and leave the moth window to the film.

2–3 weeks at best, and day-to-day — fish key on the moths when they show and vanish with them

The event happens over banks under conifers — the moths rarely reach mid-river

Recommendations come from depth structure and seasonal species behavior. Treat them as a starting point, not a guarantee. Contours here are interpolated from real agency depth surveys (state DNR / USACE). Never use for navigation. Always check local regulations.

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Recent catches at Upper Seymour Lake

Shared by DepthScout anglers. Exact spots stay private, always.

No shared catches here yet — be the first.Log a catch from the map above and share it to put Upper Seymour Lake on the board.

Fishing Upper Seymour Lake: what the data says

32-acre lake in Deer Lodge County, Montana. The lake tops out around 80 ft. The depth chart is built from real state fisheries GPS surveys, so the humps, channels and drop-offs you see are measured, not guessed. Here is how the season plays out for each species, straight from the data behind the map.

Traced from the shoreline, Upper Seymour Lake runs 41 acres with 1 miles of edge. The basin is a simple one (shoreline index 1.1) — close to a bowl, so the structure on the chart matters more than the bank. The shallow band under 15 ft claims about 35% of the surface — that's where the groceries are. Figure 0.4 mi of water from one end to the other, 0.2 mi at the beam. The water lies in Deer Lodge County. The nearest mapped water is Rainbow Lake (Deer Lodge), 10 mi to the southwest.

Brook Trout fishing at Upper Seymour Lake

Start shallow in spring: brook trout sit in 2 to 15 ft that time of year. Warm water sends them out to 10 to 30 ft; cold water stacks them in 3 to 20 ft. Top water on the chart: Main-lake point, a point in the 5 ft range, prime in spring. Fish it in early morning and the evening and you'll meet the bite. Throw a small spoon fished deep or a trolled lake-clear wobbler + worm until the fish tell you otherwise.

Season	Depth	Best window	Start at	Go-to baits
Spring	2 to 15 ft	dawn & dusk	Main-lake point (5 ft)	Small inline spinner (gold), Tiny spoon
Summer	10 to 30 ft	dawn & dusk	Break off the point (36 ft)	Small spoon fished deep, Trolled lake-clear wobbler + worm
Fall	2 to 15 ft	midday & dawn	Main-lake point (5 ft)	Small spoon (orange), Spinner
Winter	3 to 20 ft	dawn	Shallow bay flat (7 ft)	Small jigging spoon, Tungsten jig + plastic

Rainbow Trout fishing at Upper Seymour Lake

The spring pattern is a shallow one: rainbow trout in 5 to 20 ft. Midsummer fish sit out in 8 to 30 ft before dropping to 8 to 40 ft for winter. The spot to know is Break off the point, a drop-off in about 36 ft of water that rates prime for rainbow trout in winter. Plan around early morning and the evening in the warm months. Summer baits: a dodger + spoon (deep troll) or a flutter spoon gets it done.

Season	Depth	Best window	Start at	Go-to baits
Spring	5 to 20 ft	dawn & dusk	Main-lake point (5 ft)	Inline spinner (silver), Small spoon
Summer	8 to 30 ft	dawn & dusk	Shallow bay flat (7 ft)	Dodger + spoon (deep troll), Flutter spoon
Fall	10 to 35 ft	dawn & dusk	Break off the point (36 ft)	Casting spoon, Jerkbait over shoals
Winter	8 to 40 ft	dawn	Break off the point (36 ft)	Jigging spoon, Tube jig (white)

Notable structure

Count 5 structure marks on this chart. The deepest, Deep basin, sits near 78 ft.

Deep basin: deep basin, around 78 ft
Break off the point: drop-off, around 36 ft
Shallow bay flat: weed flat, around 7 ft
Main-lake point: point, around 5 ft
Back-bay flat: weed flat, around 5 ft

Upper Seymour Lake fishing regulations

Season dates, license requirements, and size and bag limits for Montana waters are set by the Montana Fish, Wildlife & Parks — and special regulations can apply to Upper Seymour Lake specifically, so confirm the current rules before you fish.

Check the official Montana fishing regulations →

Common questions

How deep is Upper Seymour Lake?

Upper Seymour Lake is about 80 ft (24 m) deep at its deepest point. The depth chart here comes from real state fisheries GPS surveys, so the contours reflect measured depths.

What fish are in Upper Seymour Lake?

Anglers target brook trout, rainbow trout on Upper Seymour Lake.

Where is the best fishing spot on Upper Seymour Lake?

Break off the point is the top-rated area: a drop-off in about 36 ft of water that rates prime for rainbow trout in winter. The map above holds the full rated-spot list for every species and season.

When is the best time to fish Upper Seymour Lake?

For brook trout, the summer bite is best in early morning and the evening. Each species page section below lists the seasonal windows, and the map shows a live NOW badge when you're inside one.

What are the fishing regulations for Upper Seymour Lake?

Fishing on Upper Seymour Lake is regulated by the Montana Fish, Wildlife & Parks. Check the official Montana regulations for current license requirements, season dates, and size and bag limits — special regulations can apply to this specific water.

Nearby waters

Rainbow Lake (Deer Lodge) 10 mi · Georgetown Lake 11 mi · Echo Lake (Granite) 14 mi · Mystic Lake 18 mi · Mussigbrod Lake 24 mi · Lily Lake (Beaverhead) 29 mi · Sand Lake 29 mi · Baldy Lake 30 mi · Bear Lake (Beaverhead) 37 mi · Tendoy Lake 39 mi · Rainbow Lake (Beaverhead) 40 mi · Brownes Lake 41 mi

See how Upper Seymour Lake stacks up: best rainbow trout lakes in Montana · best brook trout lakes in Montana

Browse all Montana fishing maps or see every water on DepthScout. Bathymetry credit: state fisheries survey programs. How we build these maps. Fish here with a sonar unit that logs? Send us your depth data and we'll improve this chart, credited to you. For fishing guidance only, never navigation.