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10-acre lake in Carbon County, Montana. The lake tops out around 35 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. Species by species, here's what the data says the year looks like.
First Rock Lake maps at 10 acres behind 0.5 miles of shoreline. Nearly circular (index 1), so the story is the bottom, not the bank. About 45% of the surface sits shallower than 15 ft — that's the weed-and-bait zone. It sits in Carbon County. If the bite dies, Second Rock Lake is 1 mi to the southwest.
Spring brook trout on First Rock Lake hold shallow, usually 2 to 15 ft. By summer they slide out to 10 to 30 ft, and by winter most fish are in 3 to 20 ft. The chart's best answer is Break off the point — drop-off, 19 ft, prime for summer. Prime time lands in early morning and the evening. The summer box starts with a small spoon fished deep or a trolled lake-clear wobbler + worm.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 15 ft | dawn & dusk | Main-lake point (4 ft) | Small inline spinner (gold), Tiny spoon |
| Summer | 10 to 30 ft | dawn & dusk | Break off the point (19 ft) | Small spoon fished deep, Trolled lake-clear wobbler + worm |
| Fall | 2 to 15 ft | midday & dawn | Main-lake point (4 ft) | Small spoon (orange), Spinner |
| Winter | 3 to 20 ft | dawn | Break off the point (19 ft) | Small jigging spoon, Tungsten jig + plastic |
Spring puts cutthroat trout in skinny water — 3 to 15 ft is the zone. Warm water sends them out to 10 to 35 ft; cold water stacks them in 9 to 35 ft. Break off the point is the standout, a drop-off at roughly 19 ft, rated prime for summer cutthroat trout. Plan around early morning and the evening in the warm months. A trolled spoon (small) or an inline spinner covers the summer program.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 15 ft | dawn & dusk | Main-lake point (4 ft) | Inline spinner (silver/gold), Small spoon |
| Summer | 10 to 35 ft | dawn & dusk | Break off the point (19 ft) | Trolled spoon (small), Inline spinner |
| Fall | 5 to 25 ft | dawn & dusk | Main-lake point (4 ft) | Casting spoon, Inline spinner |
| Winter | 9 to 35 ft | dawn | Break off the point (19 ft) | Small jigging spoon, Marabou jig |
The chart marks 3 structure features on First Rock Lake; the deepest is Deep basin at about 34 ft.
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 First Rock Lake specifically, so confirm the current rules before you fish.
Check the official Montana fishing regulations →
First Rock Lake is about 35 ft (11 m) deep at its deepest point. The depth chart here comes from real state fisheries GPS surveys, so the contours reflect measured depths.
Anglers target brook trout, cutthroat trout on First Rock Lake.
Break off the point is the top-rated area: a drop-off in about 19 ft of water that rates prime for cutthroat trout in summer. Every other rated spot, per species and season, is on the map above.
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.
Fishing on First Rock 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.
Second Rock Lake 1 mi · September Morn Lake 1 mi · Black Canyon Lake 1 mi · Lost Lake (Carbon) 2 mi · Ship Lake 3 mi · Moon Lake 3 mi · Sliderock Lake 4 mi · Two Bits Lake 4 mi · Dude Lake 4 mi · Timberline Lake 4 mi · Varve Lake (Forsaken Lake) 4 mi · Shelf Lake 4 mi
See how First Rock Lake stacks up: best brook trout lakes in Montana · best cutthroat trout lakes in Montana
More water nearby: Carbon County fishing maps (65 charts). 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.