Marmion Lake

Where Marmion Lake is

Marmion Lake lies in the District of Rainy River, with shoreline in the Town of Atikokan.

How deep is Marmion Lake?

The deepest mapped contour on Marmion Lake is 30.5 meters, and the water within that boundary descends even farther. Ontario’s bathymetry record holds 236 depth contours for Marmion Lake.

See also Ontario's Largest and Deepest Lakes

Surveyed Depths

Ontario has surveyed the depths of several thousand of its lakes over more than half a century. Later surveys were conducted by boat with satellite positioning and produced hundreds of thousands of soundings per lake. Earlier surveys were charted by running transects across the water and drawing depth contours by hand.

Water quality

Ontario’s Lake Partner Program is a volunteer monitoring network. Participants collect water samples for phosphorus analysis and measure water clarity through the summer with a Secchi disk. Most sites are sampled for phosphorus once a year, in spring, and some several times a year between spring and fall. Phosphorus in many lakes rises through the summer, so the two kinds of average are measured on different bases.

Phosphorus is the nutrient that controls how much algae a lake can grow. A lake with little phosphorus stays clear and supports cold-water fish such as lake trout. As phosphorus rises, algae increase, the water clouds, and oxygen in the deep water falls as the algae decay. The province classifies each monitoring site by its average phosphorus:

• Oligotrophic, below 10 micrograms per litre: clear water and low algae.
• Mesotrophic, from 10 to 20: moderately productive water, with more algae and weed growth than an oligotrophic lake but rarely a bloom.
• Eutrophic, above 20: nutrient-rich water, prone to algal blooms and low oxygen at depth.

No monitoring site on Marmion Lake is registered with the Lake Partner Program, so no phosphorus or clarity record exists for the lake.

A Secchi disk is a white or black-and-white plate lowered on a marked line until it disappears from view. The depth at which it vanishes is the Secchi depth, a direct measure of water clarity. Clearer water gives a deeper reading.

See also Lake Water Quality and Blue-Green Algae in Ontario

Marmion Lake Weather

The weather page for Marmion Lake carries the forecast over the water, wave heights across the lake, and the modelled water temperature.

Marmion Lake weather

Water temperature

Ontario’s aquatic resource records class Marmion Lake as a cool-water lake, with a mean depth of 6.5 meters against its maximum of 30.5.

A lake separates into layers through the summer where it is deep enough. Sunlight and wind warm and mix the upper few meters, and beneath a band of rapid cooling, the thermocline, the water stays cold. A shallow lake mixes to the bottom instead and warms through, sooner in spring and later into autumn.

No provincial monitoring station records water temperature on Marmion Lake. The LastLake model computes the temperature of its surface water for each day from the daily mean air temperature at Environment Canada’s Atikokan climate station, 18 kilometers from the lake, and from the lake’s area of 6,241 hectares and its mean depth of 6.5 meters.

Each day’s figure carries the model’s typical error for that month on lakes of the same size. The figure in the chart below is the temperature near the surface, away from the shoreline. Bays, shallows and water deeper below the surface differ in temperature. Temperature is not measured when ice covers the lake. The weather page for Marmion Lake carries the model’s figures for the past weeks and the coming week.

See also Lake Water Temperature in Ontario

Fish in Marmion Lake

Ontario’s aquatic resource records name 29 fish species in Marmion Lake.

Popular species in the province’s records

• Lake Whitefishtrout and whitefish
• Ciscotrout and whitefish
• Northern Pikepike
• Walleyeperch
• Yellow Perchperch
• Smallmouth Basssunfish
• Black Crappiesunfish
• Rock Basssunfish
• Pumpkinseedsunfish
• Bluegillsunfish
• Burbotcod

Spawning areas

Ontario maps 3 fish spawning records within the Marmion Lake outline: 3 walleye spawning areas covering 1.12 hectares.

By number of records

By area mapped

• Walleye3 areas1.1 ha

The federal Fisheries Act prohibits the harmful alteration, disruption or destruction of fish habitat without an authorization, so a dock, dredging, infill or shoreline work at a mapped spawning area is reviewed on that basis.

Stocking history

Ontario’s stocking records for Marmion Lake run from 1998 to 2000 and hold 3 releases. Walleye account for most of the fish: 11,000,000 released in three of the years between 1998 and 2000. The last recorded release was 4,000,000 walleye frys in 2000.

The province’s record of stocking for recreational fishing, kept from 2016, lists no release into Marmion Lake.

Eating the fish

The 2026 Guide to Eating Ontario Fish carries consumption advice for five species taken from Marmion Lake, tested for contaminants at a sampling location in Rainy River Dist. Each figure below is the most meals a month the guide advises for a fish of that length. Where mercury sets the advice, the figure falls as the fish gets longer, because mercury accumulates over a fish’s life. Where the guide has no result yet for certain contaminants at a location, it sets a precautionary limit of 16 meals a month. A zero means the guide advises no meals of that fish at that size.

General population: adultsSensitive population: children under fifteen, women who are or may become pregnant

Fisheries Management Zone 5

Marmion Lake lies in Fisheries Management Zone 5. Ontario sets its fishing seasons and catch limits by zone.

Fisheries management zones around Marmion Lake

Zone-wide, Smelt may not be used as bait or possessed for use as bait.

See also Fishing Seasons in Ontario, Zone by Zone and Fish Stocking in Ontario Lakes

Islands and names

Marmion Lake contains 531 islands in the Ontario Hydro Network’s outline, sixteen of them over 10 hectares and 265 under a tenth of a hectare.

Official names

Ontario’s geographic names register lists 5 official names on the water and its islands: 1 island, three bays and one narrows. A further 2 named points stand on the mainland shore.

Bays 3

• Lower Seine Bay
• Lynxhead Bay
• Sawbill Bay

Harbours, cuts and narrows 1

• Lynxhead Narrows

Points on the shore 2

• Fallenrock Point
• Gamik Point

Nearby lakes

• Eva Lake33 km away
• White Otter Lake34 km away
• Lac des Mille Lacs72 km away
• Upper Shebandowan Lake83 km away

All lakes

Questions about Marmion Lake

• How deep is Marmion Lake?

  Its deepest charted contour is 30.5 meters, and the water within it is deeper.

• How big is Marmion Lake?

  Its surface covers 62.4 square kilometers and it holds 531 islands. Of its 467 kilometers of shoreline, 248 kilometers is the mainland shore and 219 kilometers is the shore of the islands.

• What fish are in Marmion Lake?

  Ontario’s aquatic resource records name 29 species, among them walleye, smallmouth bass, northern pike, lake whitefish, yellow perch and black crappie.