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Rating depth structure for rainbow trout.
Shared by DepthScout anglers. Exact spots stay private, always.
129-acre reservoir near Franklin. The lake tops out around 13 ft. The depth picture is modeled, anchored to the true shoreline and the water's published max depth — a scouting aid, never a chart to run a boat by. Here's the year, species by species, as the scoring engine sees it.
Traced from the shoreline, Foster Reservoir runs 102 acres with 3.5 miles of edge. An index of 2.4 puts the bank firmly in maze territory: point after pocket after cove, every one a casting target. All of it is shallow-zone water — under ~15 ft across the entire basin, so the food chain has the run of the place. Call it 0.9 mi long by 0.5 mi wide at the broadest reach. The water lies in Franklin County. For a second option, Lamont Reservoir lies 2 mi southeast.
Spring cutthroat trout on Foster Reservoir hold shallow, usually 3 to 13 ft. Depth-wise the year is flat: 4 to 13 ft in summer, 3 to 13 ft once it turns cold. Put Main-lake point first on the milk run — a point near 8 ft that grades prime for fall. The feeding windows run early morning and the evening. The summer box starts with a trolled spoon (small) or an inline spinner.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 13 ft | dawn & dusk | Main-lake point (8 ft) | Inline spinner (silver/gold), Small spoon |
| Summer | 4 to 13 ft | dawn & dusk | Main-lake point (8 ft) | Trolled spoon (small), Inline spinner |
| Fall | 3 to 13 ft | dawn & dusk | Main-lake point (8 ft) | Casting spoon, Inline spinner |
| Winter | 3 to 13 ft | dawn | Deep basin (11 ft) | Small jigging spoon, Marabou jig |
Start shallow in spring: rainbow trout sit in 3 to 13 ft that time of year. They don't go far with the seasons — 3 to 13 ft covers summer, 3 to 13 ft covers winter. Top water on the chart: Main-lake point, a point in the 8 ft range, prime in spring. Fish it in early morning and the evening and you'll meet the bite. Throw a dodger + spoon (deep troll) or a flutter spoon until the fish tell you otherwise.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 13 ft | dawn & dusk | Main-lake point (8 ft) | Inline spinner (silver), Small spoon |
| Summer | 3 to 13 ft | dawn & dusk | Main-lake point (8 ft) | Dodger + spoon (deep troll), Flutter spoon |
| Fall | 4 to 13 ft | dawn & dusk | Main-lake point (8 ft) | Casting spoon, Jerkbait over shoals |
| Winter | 3 to 13 ft | dawn | Deep basin (11 ft) | Jigging spoon, Tube jig (white) |
Structure-wise the chart holds 5 features, led in depth by Deep basin at roughly 11 ft.
| Date | Species | Count | Size |
|---|---|---|---|
| Mar 11 | Rainbow Trout | — | ~13" |
Source: Idaho Fish & Game stocking records, retrieved 2026-09-03.
Season dates, license requirements, and size and bag limits for Idaho waters are set by the Idaho Fish and Game — and special regulations can apply to Foster Reservoir specifically, so confirm the current rules before you fish.
Check the official Idaho fishing regulations →
Foster Reservoir is about 13 ft (4 m) deep at its deepest point. The contours here are modeled from the water's real shape and maximum depth, so treat them as a rough guide.
Anglers target cutthroat trout, rainbow trout on Foster Reservoir.
Main-lake point is the top-rated area: a point in about 8 ft of water that rates prime for cutthroat trout in fall. Every other rated spot, per species and season, is on the map above.
For cutthroat 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.
Yes — per Idaho Fish & Game stocking records records, Foster Reservoir was most recently stocked Mar 11 with rainbow trout. The full stocking history is listed above.
Fishing on Foster Reservoir is regulated by the Idaho Fish and Game. Check the official Idaho regulations for current license requirements, season dates, and size and bag limits — special regulations can apply to this specific water.
Lamont Reservoir 2 mi · Treasureton Reservoir 8 mi · Oneida Narrows Reservoir 13 mi · Newton Reservoir 17 mi, UT · Bear Lake 28 mi, UT/ID · Hyrum Reservoir 35 mi, UT · Porcupine Reservoir 42 mi, UT · Mantua Reservoir 43 mi, UT · Stone Reservoir 44 mi · Birch Creek Reservoir 50 mi, UT · Willard Bay Reservoir 53 mi, UT · Chesterfield Reservoir 53 mi
See how Foster Reservoir stacks up: best rainbow trout lakes in Idaho · best cutthroat trout lakes in Idaho
Browse all Idaho fishing maps or see every water on DepthScout. 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.