Long Lake

Where Long Lake is

Long Lake lies in the District of Sudbury, with shoreline in the City of Greater Sudbury.

How deep is Long Lake?

Long Lake reaches a maximum recorded depth of 38.5 meters, determined from 57,928 soundings.

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.

Long Lake has 13 Lake Partner monitoring sites. Nine have reported phosphorus for the three or more years the province requires before a status is assigned. Seven of those sites are classified oligotrophic and two mesotrophic.

The longest record is held by site 2784/8 at NE End, deep spot, with phosphorus sampled once a year over 13 years to 2025. Its long-term mean phosphorus concentration is 8.55 micrograms per litre, within the oligotrophic band, which extends to 10.

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.

The 157 clarity readings at site 2784/8 give a median Secchi depth of 4.0 meters.

Median Secchi depth by year at site 2784/8

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

Long Lake Weather

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

Long Lake weather

Water temperature

Ontario’s aquatic resource records class Long Lake as a warm-water lake, with a mean depth of 9.3 meters against its maximum of 38.5.

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 Long Lake. The LastLake model computes the temperature of its surface water for each day from the daily mean air temperature at Environment Canada’s Sudbury A climate station, 36 kilometers from the lake, or the next nearest station when its record is incomplete, and from the lake’s area of 867 hectares and its mean depth of 9.3 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 Long Lake carries the model’s figures for the past weeks and the coming week.

See also Lake Water Temperature in Ontario

Fish in Long Lake

Ontario’s aquatic resource records name 16 fish species in Long Lake. The province’s other records for the lake name one further species, brook trout. It appears in the records below.

Popular species in the province’s records

• Lake Trouttrout and whitefish
• Ciscotrout and whitefish
• Northern Pikepike
• Walleyeperch
• Yellow Perchperch
• Smallmouth Basssunfish
• Largemouth Basssunfish
• Pumpkinseedsunfish
• Brown Bullheadcatfish

Stocking history

Ontario’s stocking records for Long Lake run from 1946 to 2005 and hold 54 releases. Walleye account for most of the fish: 2,585,600 released in ten of the years between 1946 and 2005. The last recorded release was 10,000 walleye fingerlings in 2005.

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

Eating the fish

The 2026 Guide to Eating Ontario Fish carries consumption advice for eight species taken from Long Lake, tested for contaminants at a sampling location in Main basins, Eden & Broder Twps., Sudbury 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. 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 10

Long Lake lies in Fisheries Management Zone 10. Ontario sets its fishing seasons and catch limits by zone.

Fisheries management zones around Long Lake

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

Long Lake Ice Fishing

An ice hut on Long Lake must be removed by March 31. The province sets dates for ice hut removal as a safety measure to ensure huts are removed before thawing occurs. One date applies to an entire fisheries management zone (FMZ). Long Lake lies within FMZ 10.

An ice hut must also be removed before the ice breaks up, whether or not that date has passed. The deadline clears huts from the ice ahead of the thaw and does not close the fishing season.

Registration is required in FMZ 10 for an ice hut built of anything other than fabric, and for a fabric tent covering seven square meters or more. Registration is free, and the number is displayed on the outside of the hut.

Ice conditions

No public record reports the thickness or the condition of the ice on Long Lake on any given day. Ontario publishes ice safety guidance for anyone going out on the ice, at ontario.ca.

See also Lake Ice in Ontario and When the Lakes Will Freeze This Winter

Islands and names

Long Lake contains twelve islands in the Ontario Hydro Network’s outline, zero of them over 10 hectares and eight under a tenth of a hectare.

Official names

Ontario’s geographic names register lists 3 official names on the water and its islands: 1 island.

Nearby lakes

• Nepahwin Lake14 km away
• Ramsey Lake17 km away
• Richard Lake17 km away
• Lake Panache24 km away

All lakes

Questions about Long Lake

• How deep is Long Lake?

  Its maximum recorded depth is 38.5 meters.

• How big is Long Lake?

  Its surface covers 8.7 square kilometers and it holds 12 islands. Of its 52 kilometers of shoreline, 50 kilometers is the mainland shore and 2 kilometers is the shore of the islands.

• What fish are in Long Lake?

  Ontario’s aquatic resource records name sixteen species, among them lake trout, walleye, smallmouth bass, largemouth bass, northern pike and yellow perch. The lake’s spawning, consumption and stocking records also name brook trout.