Thirty Island Lake Depth Map & Fishing Spots (ON)

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Lake depth chart

Thirty Island Lake, ON

Max 105 ft

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Where to start

Hopper & ant season (windward banks) window is on — see the hatch outlook

Hatch outlook

Hopper & ant season (windward banks)Active window

Typical here: Jul 1 – Sep 15 · hoppers peak July–August; winged-ant falls show up on warm humid afternoons — a wind event, not a hatch

adultwarm, breezy afternoons, roughly 1–5pm — slap the imitation down hard — the splat is the trigger — then wait; count to three after the rise before setting

Work the windward bank on breezy summer afternoons — that's where the food is. Casting-bubble-and-hopper is the direct translation; otherwise run small topwaters and inline spinners tight along the grass edges and blowdown banks in the afternoon warmth.

The event happens over windward grassy banks, overhanging brush and blowdowns — wherever the breeze dumps the bugs

Fall shiner runActive window

Typical here: Sep 1 – Oct 31 · same push on the Ontario side — Simcoe's shiners migrate shallow as the water cools, and the predators ride with them

adultdaylight for the jig bite; after dark the shiners stack under dock lights with walleyes and pike mixed right in — follow the bait, not the spot — millions of shiners move together and the predators ride with them; silver profile and flash matter

Concentrates hard but travels — the school (and the walleyes under it) can be off a river mouth one week and miles upriver the next.

Jig-and-minnow is the event's signature — a frozen emerald shiner on a 1/4 oz jig drifted along the run; silver jerkbaits and trolled crankbaits take the roaming fish; blade baits under the schools.

The event happens over river mouths and the first miles upriver, warming shallow shorelines, and rocky points where the displaced bait stacks

Next on this water

Hex (giant mayfly) · mayflyMay 25 – Aug 10 · in ~9 months

June mayfly hatch (walleye lakes) · mayflyJun 1 – Aug 10 · in ~9 months

Recommendations come from depth structure and seasonal species behavior. Treat them as a starting point, not a guarantee. Contours on this water are approximations. Never use for navigation. Always check local regulations.

Depth · ft

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Recent catches at Thirty Island Lake

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Fishing Thirty Island Lake: what the data says

507-acre lake in Frontenac County, Ontario. The lake tops out around 105 ft. Bathymetry on this water is estimated from its real outline and maximum depth. Use it to shortlist water, then verify with your electronics — and never navigate by it. Here is how the season plays out for each species, straight from the data behind the map.

Thirty Island Lake maps at 513 acres behind 11.1 miles of shoreline, with a single island in the mix. That shoreline is heavily fingered (development index 3.5) — bays, points and pockets everywhere, which multiplies the fishable edge. Littoral water — the productive band under ~15 ft — makes up 22% of this chart, as modeled. Tip to tip the water measures near 2 mi with a 1-mi widest point. Frontenac County claims this one. If the bite dies, Sangster Lake is 1 mi to the northeast.

Cisco (Lake Herring) fishing at Thirty Island Lake

Start shallow in spring: cisco (lake herring) sit in 10 to 40 ft that time of year. Warm water sends them out to 40 to 80 ft; cold water stacks them in 20 to 60 ft. Top water on the chart: Deep basin, a deep basin in the 89 ft range, prime in summer. Fish it in early morning and you'll meet the bite. Throw a vertical flutter spoon (small) or a drop-shot micro plastic until the fish tell you otherwise.

Season	Depth	Best window	Start at	Go-to baits
Spring	10 to 40 ft	dawn & dusk	Deep basin (89 ft)	Small silver spoon, Tiny swim jig (white)
Summer	40 to 80 ft	dawn	Deep basin (89 ft)	Vertical flutter spoon (small), Drop-shot micro plastic
Fall	5 to 25 ft	dusk & dawn	open water	Small casting spoon, Inline spinner (silver)
Winter	20 to 60 ft	dawn	Break off the point (47 ft)	Small jigging spoon (glow/silver), Tungsten jig + minnow head

Yellow Perch fishing at Thirty Island Lake

The spring pattern is a shallow one: yellow perch in 3 to 12 ft. As the season builds they drop to 10 to 30 ft, wintering in 15 to 35 ft. Top water on the chart: Shallow bay flat, a weed flat in the 6 ft range, prime in spring. Time it for early morning. Summer baits: a drop-shot micro plastics or a small spoon tipped with worm gets it done.

Season	Depth	Best window	Start at	Go-to baits
Spring	3 to 12 ft	midday & dawn	Shallow bay flat (6 ft)	Small jig + curly tail, Perch-pattern micro crank
Summer	10 to 30 ft	dawn	Shallow bay flat (6 ft)	Drop-shot micro plastics, Small spoon tipped with worm
Fall	12 to 35 ft	midday	Deep basin (89 ft)	Jigging spoon (small), Perch rig / spreader
Winter	15 to 35 ft	midday & dawn	Deep basin (89 ft)	Tungsten jig + spikes, Rattle spoon (small)

Northern Pike fishing at Thirty Island Lake

When the water first warms, northern pike slide up into 2 to 8 ft. By summer they slide out to 8 to 20 ft, and by winter most fish are in 5 to 15 ft. If you only fish one area, make it Shallow bay flat: a weed flat around 6 ft that scores prime in spring. In summer the feeding windows fall in early morning and the evening. Keep a bucktail or a weedless spoon over cabbage rigged through the warm months.

Season	Depth	Best window	Start at	Go-to baits
Spring	2 to 8 ft	midday & dawn	Shallow bay flat (6 ft)	#5 inline spinner, Spoon (red/white)
Summer	8 to 20 ft	dawn & dusk	Shallow bay flat (6 ft)	Bucktail, Weedless spoon over cabbage
Fall	6 to 18 ft	midday & dawn	Shallow bay flat (6 ft)	Big rubber (Bull Dawg style), Husky-style jerkbait
Winter	5 to 15 ft	midday	Shallow bay flat (6 ft)	Tip-ups, Large jigging spoon

Smallmouth Bass fishing at Thirty Island Lake

When the water first warms, smallmouth bass slide up into 3 to 12 ft. By summer they slide out to 10 to 30 ft, and by winter most fish are in 20 to 45 ft. If you only fish one area, make it Main-lake point: a point around 26 ft that scores prime in fall. In summer the feeding windows fall in early morning and the evening. Keep a drop shot (goby/minnow) or a ned rig rigged through the warm months.

Season	Depth	Best window	Start at	Go-to baits
Spring	3 to 12 ft	dawn & dusk	open water	Ned rig, Tube jig
Summer	10 to 30 ft	dawn & dusk	Main-lake point (26 ft)	Drop shot (goby/minnow), Ned rig
Fall	8 to 25 ft	midday & dawn	Main-lake point (26 ft)	Jerkbait, Blade bait
Winter	20 to 45 ft	midday	Break off the point (47 ft)	Blade bait, Hair jig

Largemouth Bass fishing at Thirty Island Lake

Come spring, look for largemouth bass tight to the bank in 2 to 10 ft. Expect a summer slide to 8 to 20 ft, then a winter hold in 15 to 35 ft. Start at Shallow bay flat. It's a weed flat holding about 6 ft of water and rates prime come spring. Prime time lands in early morning and the evening. A texas-rigged 10" worm or a deep-diving crankbait is the honest summer answer here.

Season	Depth	Best window	Start at	Go-to baits
Spring	2 to 10 ft	dawn & dusk	Shallow bay flat (6 ft)	Spinnerbait, Chatterbait
Summer	8 to 20 ft	dawn & dusk	Shallow bay flat (6 ft)	Texas-rigged 10" worm, Deep-diving crankbait
Fall	4 to 15 ft	midday & dawn	Shallow bay flat (6 ft)	Squarebill crankbait (shad), Spinnerbait
Winter	15 to 35 ft	midday	Break off the point (47 ft)	Blade bait, Jigging spoon

Rock Bass fishing at Thirty Island Lake

Start shallow in spring: rock bass sit in 2 to 10 ft that time of year. Warm water sends them out to 5 to 20 ft; cold water stacks them in 12 to 30 ft. Top water on the chart: Main-lake point, a point in the 26 ft range, good in fall. Fish it in the evening and you'll meet the bite. Throw a ned rig (small) or a marabou jig until the fish tell you otherwise.

Season	Depth	Best window	Start at	Go-to baits
Spring	2 to 10 ft	midday & dawn	open water	1/16 oz jig + grub, Small inline spinner
Summer	5 to 20 ft	dusk	Main-lake point (26 ft)	Ned rig (small), Marabou jig
Fall	8 to 22 ft	midday	Main-lake point (26 ft)	Small tube jig, Inline spinner
Winter	12 to 30 ft	midday	Deep basin (89 ft)	Tungsten jig + plastic, Small spoon + spike

Thirty Island Lake also holds bluegill (4 to 15 ft in summer), pumpkinseed (2 to 10 ft in summer), burbot (32 to 105 ft in summer). Pick any of them on the map above for rated spots and bait picks.

Notable structure

Structure-wise the chart holds 6 features, led in depth by Deep basin at roughly 89 ft.

Deep basin: deep basin, around 89 ft
Break off the point: drop-off, around 47 ft
Main-lake point: point, around 26 ft
Secondary point: point, around 26 ft
Shallow bay flat: weed flat, around 6 ft
Back-bay flat: weed flat, around 6 ft

Thirty Island Lake fishing regulations

Season dates, license requirements, and size and bag limits for Ontario waters are set by the Ontario fishing regulations (FMZ summary) — and special regulations can apply to Thirty Island Lake specifically, so confirm the current rules before you fish.

Check the official Ontario fishing regulations →

Common questions

How deep is Thirty Island Lake?

Thirty Island Lake is about 105 ft (32 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.

What fish are in Thirty Island Lake?

Anglers target cisco (lake herring), yellow perch, northern pike, smallmouth bass, largemouth bass, rock bass, bluegill, pumpkinseed, burbot on Thirty Island Lake.

Where is the best fishing spot on Thirty Island Lake?

Shallow bay flat is the top-rated area: a weed flat in about 6 ft of water that rates prime for yellow perch in spring. Every other rated spot, per species and season, is on the map above.

When is the best time to fish Thirty Island Lake?

For cisco (lake herring), the summer bite is best in early morning. 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 Thirty Island Lake?

Fishing on Thirty Island Lake is regulated by the Ontario fishing regulations (FMZ summary). Check the official Ontario regulations for current license requirements, season dates, and size and bag limits — special regulations can apply to this specific water.

Nearby waters

Sangster Lake 1 mi · Sand Lake 1 mi · Miner Lake 2 mi · White Lake 2 mi · Potspoon Lake 2 mi · Thirteen Island Lake 2 mi · Desert Lake 2 mi · Canoe Lake 3 mi · Birch Lake 3 mi · Arkon Lake 3 mi · Kingsford Lake 4 mi · Garter Lake 4 mi

See how Thirty Island Lake stacks up: best largemouth bass lakes in Ontario · best smallmouth bass lakes in Ontario · best northern pike lakes in Ontario · best bluegill lakes in Ontario

More water nearby: Frontenac County fishing maps (127 charts). Browse all Ontario 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.