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26-acre lake near Marshall County. The lake tops out around 23 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.
Drawn out, this is 26 acres of water rimmed by 0.8 miles of bank. The basin is a simple one (shoreline index 1.2) — close to a bowl, so the structure on the chart matters more than the bank. Roughly 90% of the water is 15 ft or less, the band where the food chain lives. Call it 0.3 mi long by 0.2 mi wide at the broadest reach. The water lies in Marshall County. Closest neighbour on DepthScout: Mariposa Lake, 12 mi southwest of here.
Start shallow in spring: crappie sit in 2 to 8 ft that time of year. Summer pushes them deeper, 7 to 23 ft, and winter fish settle into 7 to 23 ft. The spot to know is Deep basin, a deep basin in about 23 ft of water that rates prime for crappie in winter. Warm-month bites cluster around early morning and the evening. Throw a jig trolled/spider-rigged or a small crankbait (trolled) until the fish tell you otherwise.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 8 ft | midday & dawn | Shallow bay flat (2 ft) | 1/16 oz jig + tube, Curly-tail grub |
| Summer | 7 to 23 ft | dawn & dusk | Break off the point (9 ft) | Jig trolled/spider-rigged, Small crankbait (trolled) |
| Fall | 8 to 20 ft | dawn | Break off the point (9 ft) | Jig + minnow combo, Small swimbait (1.5-2") |
| Winter | 7 to 23 ft | midday | Deep basin (23 ft) | Tungsten jig + soft plastic, Tiny jigging spoon |
In spring, bluegill run shallow here, mostly 1 to 6 ft. Summer pushes them deeper, 4 to 15 ft, and winter fish settle into 7 to 23 ft. Shallow bay flat is the standout, a weed flat at roughly 2 ft, rated prime for spring bluegill. Time it for early morning and the evening. You won't need more than a small sponge spider (fly) or a micro tube jig most summer days.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 1 to 6 ft | midday & dusk | Shallow bay flat (2 ft) | 1/32 oz jig + micro plastic, Tiny popper (evenings) |
| Summer | 4 to 15 ft | dawn & dusk | Shallow bay flat (2 ft) | Small sponge spider (fly), Micro tube jig |
| Fall | 6 to 18 ft | midday | Break off the point (9 ft) | Micro jig + waxworm, Small spoon tipped |
| Winter | 7 to 23 ft | midday | Deep basin (23 ft) | Tungsten ice jig + plastic, Tiny spoon |
The spring pattern is a shallow one: largemouth bass in 2 to 10 ft. As the season builds they drop to 8 to 20 ft, wintering in 7 to 23 ft. Top water on the chart: Shallow bay flat, a weed flat in the 2 ft range, prime in spring. Time it for early morning and the evening. Summer baits: a texas-rigged 10" worm or a deep-diving crankbait gets it done.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 10 ft | dawn & dusk | Shallow bay flat (2 ft) | Spinnerbait, Chatterbait |
| Summer | 8 to 20 ft | dawn & dusk | Break off the point (9 ft) | Texas-rigged 10" worm, Deep-diving crankbait |
| Fall | 4 to 15 ft | midday & dawn | Main-lake point (2 ft) | Squarebill crankbait (shad), Spinnerbait |
| Winter | 7 to 23 ft | midday | Break off the point (9 ft) | Blade bait, Jigging spoon |
The spring pattern is a shallow one: channel catfish in 3 to 12 ft. As the season builds they drop to 7 to 23 ft, wintering in 7 to 23 ft. Top water on the chart: Deep basin, a deep basin in the 23 ft range, prime in winter. Time it for after dark and the evening.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 12 ft | dusk | Shallow bay flat (2 ft) | |
| Summer | 7 to 23 ft | night & dusk | Deep basin (23 ft) | |
| Fall | 7 to 23 ft | dusk | Deep basin (23 ft) | |
| Winter | 7 to 23 ft | midday | Deep basin (23 ft) |
Come spring, look for yellow perch tight to the bank in 3 to 12 ft. Expect a summer slide to 7 to 23 ft, then a winter hold in 7 to 23 ft. Start at Deep basin. It's a deep basin holding about 23 ft of water and rates prime come fall. Prime time lands in early morning. A drop-shot micro plastics or a small spoon tipped with worm is the honest summer answer here.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 12 ft | midday & dawn | Shallow bay flat (2 ft) | Small jig + curly tail, Perch-pattern micro crank |
| Summer | 7 to 23 ft | dawn | Deep basin (23 ft) | Drop-shot micro plastics, Small spoon tipped with worm |
| Fall | 7 to 23 ft | midday | Deep basin (23 ft) | Jigging spoon (small), Perch rig / spreader |
| Winter | 7 to 23 ft | midday & dawn | Deep basin (23 ft) | Tungsten jig + spikes, Rattle spoon (small) |
Come spring, look for walleye tight to the bank in 4 to 15 ft. They move out to 7 to 23 ft in summer and finish the year down in 7 to 23 ft. If you only fish one area, make it Break off the point: a drop-off around 9 ft that scores prime in fall. Best bite is the evening and early morning. A crawler harness on bottom bouncer or a deep crankbait (trolled) is the honest summer answer here.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 4 to 15 ft | dusk & dawn | Break off the point (9 ft) | 1/8 oz jig + minnow, Hair jig |
| Summer | 7 to 23 ft | dusk & dawn | Break off the point (9 ft) | Crawler harness on bottom bouncer, Deep crankbait (trolled) |
| Fall | 7 to 23 ft | dusk & night | Break off the point (9 ft) | Jigging rap, Jig + big minnow |
| Winter | 7 to 23 ft | dusk & dawn | Deep basin (23 ft) | Jigging spoon + minnow head, Rattle bait |
Green Castle Lake carries 4 mapped structure features, topping out (or rather bottoming out) at Deep basin, about 23 ft down.
Access data: OpenStreetMap contributors (ODbL) — community-mapped launches. Confirm conditions and fees locally before you launch.
Season dates, license requirements, and size and bag limits for Iowa waters are set by the Iowa DNR — and special regulations can apply to Green Castle Lake specifically, so confirm the current rules before you fish.
Check the official Iowa fishing regulations →
Green Castle Lake is about 23 ft (7 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 crappie, bluegill, largemouth bass, channel catfish, yellow perch, walleye on Green Castle Lake. This isn't a survey of the water — none is published for it — but an informed estimate from the species common to the region, narrowed by this water's depth, size and each species' range.
Deep basin is the top-rated area: a deep basin in about 23 ft of water that rates prime for crappie in winter. Every other rated spot, per species and season, is on the map above.
For crappie, 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 Green Castle Lake is regulated by the Iowa DNR. Check the official Iowa regulations for current license requirements, season dates, and size and bag limits — special regulations can apply to this specific water.
Mariposa Lake 12 mi · Rock Creek Lake 12 mi · Arbor Lake 15 mi · Union Grove Lake 16 mi · Otter Creek Lake 19 mi · Hickory Grove Lake 26 mi · Diamond Lake 28 mi · Lower Pine Lake 32 mi · Upper Pine Lake 33 mi · Iowa River 33 mi · Roberts Creek Lake 36 mi · Casey Lake (aka Hickory Hills Lake) 36 mi
See how Green Castle Lake stacks up: best largemouth bass lakes in Iowa · best walleye lakes in Iowa · best crappie lakes in Iowa · best bluegill lakes in Iowa
Browse all Iowa 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.