Mary Lake
45.2443° N, 79.2584° W
Depth contours from the 2003 government survey. Not for navigation.
Download the depth map (SVG)Mary Lake, Ontario. 45.2443° N, 79.2584° W
Maximum depth 58 m (2003 survey). Scale bar on the map.
Not for navigation. Depths are from government surveys and may be outdated.
borealbound.ca/lakes/on/mary-lake/, compiled October 9, 2026
- Canadian Geographical Names Database, Natural Resources Canada. Contains information licensed under the Open Government Licence – Canada.
- HydroLAKES v1.0, Messager et al. 2016 / WWF HydroSHEDS. Licensed under CC BY 4.0.
- Census boundaries and population, 2021, Statistics Canada. Adapted from Statistics Canada. This does not constitute an endorsement by Statistics Canada.
- Aquatic Resource Area survey points, Ontario Ministry of Natural Resources. Contains information licensed under the Open Government Licence – Ontario.
- Fish stocking for recreational purposes, Ontario Ministry of Natural Resources. Contains information licensed under the Open Government Licence – Ontario.
- Fishing access points, Ontario Ministry of Natural Resources. Contains information licensed under the Open Government Licence – Ontario.
- Fisheries Management Zones, Ontario Ministry of Natural Resources. Contains information licensed under the Open Government Licence – Ontario.
- Lake Partner Program, Ontario Ministry of the Environment, Conservation and Parks. Contains information licensed under the Open Government Licence – Ontario.
- Bathymetry lines and survey index, Ontario Ministry of Natural Resources. Contains information licensed under the Open Government Licence – Ontario.
- Real-time hydrometric data, Environment and Climate Change Canada. Contains data from Environment and Climate Change Canada (ECCC Data Servers End-use Licence).
- National Water Data Archive (HYDAT) daily means, Environment and Climate Change Canada. Contains data from Environment and Climate Change Canada (ECCC Data Servers End-use Licence).
- City page weather forecasts and alerts, Environment and Climate Change Canada. Contains data from Environment and Climate Change Canada (ECCC Data Servers End-use Licence).
- Air Quality Health Index observations and forecasts, Environment and Climate Change Canada. Contains data from Environment and Climate Change Canada (ECCC Data Servers End-use Licence).
- Guide to Eating Ontario Fish: Advisory Database, Ontario Ministry of the Environment, Conservation and Parks. Contains information licensed under the Open Government Licence – Ontario.
Mary Lake is 58 m deep at its deepest point, deeper than 96% of the 2,688 surveyed lakes in Ontario. It covers 10.7 km² and lies beside Port Sydney.
Government surveys have recorded 15 fish species here, including rock bass, smallmouth bass and yellow perch.
- Maximum depth
- 58 msurveyed 2003
- deeper than 96% of the 2,688 surveyed lakes in Ontario
- Area
- 10.7 km²
- larger than 95% of the 18,731 lakes in Ontario
- Shoreline
- 21.3 km
- longer than 88% of the 18,731 lakes in Ontario
- Water clarity
- 3 mSecchi depth, 2025
- less clear than 61% of the 1,251 monitored lakes in Ontario
- Fish species
- 15
- more than 89% of the 2,454 surveyed lakes in Ontario
- Elevation
- 280 m
Today on the water
8.2 °C
Observed at Huntsville, as of 3:00 a.m. EDT
choppy Estimated waves, next 12 hours: up to 0.3 m. Around 12 p.m., wind from the northwest: the northwest shore is sheltered, waves build toward the southeast shore.
| Time | 4 a.m. | 7 a.m. | 10 a.m. | 1 p.m. | 4 p.m. | 7 p.m. | 10 p.m. | 1 a.m. |
|---|---|---|---|---|---|---|---|---|
| Wind km/h | W 15 | W 15 | W 15 | NW 30 | NW 30 | NW 15 | var. 5 | var. 5 |
| Gusts km/h | 50 | 50 | ||||||
| Waves (est.) m | 0.2 | 0.2 | 0.2 | 0.3 | ||||
| Temp. °C | 2 | 3 | 7 | 11 | 13 | 10 | 6 | 2 |
| Precip. % | 40 | 40 | 40 | 40 | 20 | 20 | 0 | 0 |
Tonight: Partly cloudy with 60 percent chance of showers. Risk of a thunderstorm early this evening. Wind west 30 km/h gusting to 50 becoming light this evening. Low plus 2.
Weather: Huntsville (local forecast), as of 3:02 a.m. EDT
Water level
Mary Lake at Port Sydney: 8.5 m at 1:45 a.m. EDT: 2 cm below the median for this time of year, within the normal range.
Normal range (25th–75th percentile, HYDAT) Last 7 days
Provisional real-time data, subject to revision. hydrometric station 02EB021
Sun and moon
- Civil dawn
- 6:55 a.m.
- Sunrise
- 7:25 a.m.
- Sunset
- 6:42 p.m.
- Civil dusk
- 7:11 p.m.
- Moonrise
- 6:17 a.m.
- Moonset
- 6:00 p.m.
- Moon
- Waning crescent, 1% lit
Air Quality Health Index
2 low risk
Dorset, as of 2:00 a.m. EDT
Follow this lake by email: a weekly summary of conditions.
Depth
10% of Mary Lake is shallower than 3 m, and 37% is deeper than 30 m.
How to read it: the lake’s area is sorted from the shore to the deepest point. Where the curve is flat, large areas share one depth (flats and weed beds); where it drops, depth changes quickly (drop-offs).
The government depth survey from 2003 records a maximum depth of 58 m, drawn from 239 depth contours.
- Download the depth map (SVG)Printing this page gives the map on one sheet, with scale and sources.
Not for navigation. Depths are from government surveys and may be outdated.
Fish
Sport fish by the share of the 35 government surveys (2013–2013) that recorded them.
Forage fish and other species (6)
Forage fish
- Rainbow Smelt 14
- Trout-Perch 8
- Spottail Shiner 4
- Bluntnose Minnow 3
- Slimy Sculpin 2
Other
- White Sucker 1
Numbers are the surveys that recorded each species.
Stocking
Lake Trout6,850 fish in 6 years, most recently 2025
All stocking records (6)
| Year | Species | Fish | Stage |
|---|---|---|---|
| 2025 | Lake Trout | 2,000 | Yearlings |
| 2024 | Lake Trout | 850 | Yearlings |
| 2022 | Lake Trout | 1,000 | Yearlings |
| 2020 | Lake Trout | 1,000 | Yearlings |
| 2018 | Lake Trout | 1,000 | Yearlings |
| 2016 | Lake Trout | 1,000 | Yearlings |
Eating your catch
The provincial guide to eating fish (2026) sets limits for 7 species from Mary Lake. Maximum meals per month:
| Species | Length | General population | Sensitive population* | Contaminant |
|---|---|---|---|---|
| Lake Trout | 50-55 cm | 2 | Do not eat | Mercury |
| Northern Pike | 60-65 cm | 4 | Do not eat | Mercury |
| Rock Bass | 15-20 cm | 4 | Do not eat | Mercury |
| Smallmouth Bass | 35-40 cm | 2 | Do not eat | Chromium |
| Walleye | 40-45 cm | 4 | Do not eat | Mercury |
| Yellow Perch | 20-25 cm | 4 | Do not eat | Mercury |
| Rainbow Smelt | 15-20 cm | 8 | 4 | Mercury |
* As defined in the guide, including children and people who are or may become pregnant. Limits are for the length the guide lists most often; they change with the size of the fish. Read the official guide
Fishing regulations: Fisheries Management Zone 15. Check seasons and limits before you fish.
Water
Clarity was measured with a Secchi disk in 31 years between 1995 and 2025; the latest annual mean is 3 m.
Getting on the water
2 listed boat launches; 1 with parking listed. marks launches on the map.
North end
- Mary Lake - North Mary Lake Road
South end
- Mary Lake - Port Sydney
Follow this lake
Every Friday by email: the Environment Canada forecast, the water level at the nearest gauge and any weather alerts in effect.