Lake Opeongo

Where Lake Opeongo is

Lake Opeongo lies in the District of Nipissing.

How deep is Lake Opeongo?

Ontario’s digital bathymetry records hold no soundings and no depth contours within the Ontario Hydro Network’s outline of Lake Opeongo. Ontario’s aquatic resource record for Lake Opeongo gives a maximum depth of 49.4 meters and a mean depth of 13.7 meters.

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 Lake Opeongo 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

Lake Opeongo Weather

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

Lake Opeongo weather

Water temperature

Ontario’s aquatic resource records class Lake Opeongo as a cold-water lake, with a mean depth of 13.7 meters.

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 Lake Opeongo. The weather page for Lake Opeongo carries the LastLake model’s surface water temperature for each day of the coming week. The province’s longest in-water record is kept on eight research lakes near Dorset, sampled since 1976. A reading is taken at the surface, at one meter, at each meter to seven and then every two meters to the bottom, about every two weeks through the open-water season and about monthly under ice. The record holds 5,240 readings at a depth of one meter.

At one meter the eight lakes track one another closely. On a day when several were sampled, the warmest and the coolest lake differed by about one degree in every month of the year, and a 12 meter deep lake and a 37 meter deep lake read within 0.2 degrees of each other from June to October. The weather of the year, and not the lake, sets most of the width of the band below.

Water temperature at a depth of one meter (eight lakes near Dorset, ON)

How depth changes the temperature

The chart below is the province’s record on Harp Lake, 37 meters deep, drawn as the median temperature at each depth for each month over 49 years. In July the water at one meter is 23 degrees, at five meters 15, at seven meters 9, and from 13 meters to the bottom under 6. By October the warm layer has deepened to seven meters and cooled to 11 degrees. In February the whole column sits between 1 and 4 degrees under the ice, coldest at the top.

A shallower lake in the same record warms sooner. Heney Lake, six meters deep, reads about 1.8 degrees warmer than Harp Lake at one meter from January to May, 0.8 degrees warmer from June to August, and the same or cooler from September.

See also Lake Water Temperature in Ontario

Fish in Lake Opeongo

Ontario’s aquatic resource records name 30 fish species in Lake Opeongo. The province’s other records for the lake name one further species, splake. It appears in the records below.

Popular species in the province’s records

• Lake Trouttrout and whitefish
• Brook Trouttrout and whitefish
• Lake Whitefishtrout and whitefish
• Ciscotrout and whitefish
• Round Whitefishtrout and whitefish
• Yellow Perchperch
• Smallmouth Basssunfish
• Pumpkinseedsunfish
• Burbotcod
• Brown Bullheadcatfish

Spawning areas

Ontario maps 12 fish spawning records within the Lake Opeongo outline: 12 lake trout spawning areas covering 0.35 hectares.

By number of records

By area mapped

• Lake Trout12 areas0.3 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 Lake Opeongo run from 1950 to 1981 and hold 28 releases. Lake Trout account for most of the fish: 131,128 released in ten of the years between 1950 and 1973. The last recorded release was 800 brook trout yearlings in 1981.

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

Eating the fish

The 2026 Guide to Eating Ontario Fish carries consumption advice for six species taken from Lake Opeongo, tested for contaminants at a sampling location in Bower Twp., Nipissing 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 15

Lake Opeongo lies in Fisheries Management Zone 15. Ontario sets its fishing seasons and catch limits by zone. The province describes it as a zone of many natural lake trout and brook trout lakes, with a well-developed road network and moderate angling effort.

Fisheries management zones around Lake Opeongo

Where a row reads zone-wide, the zone’s own season or limit above applies.

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

Lake Opeongo Ice Fishing

An ice hut on Lake Opeongo 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). Lake Opeongo lies within FMZ 15.

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 15 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 Out Date

The ice has been recorded leaving Lake Opeongo in 41 springs between 1964 and 2004. The median date is April 30. The earliest recorded break-up is April 12 in 1981, and the latest is May 16 in 1972.

Across the 41 recorded springs the date has moved earlier by about 1.9 days each decade.

The record was contributed by Peter J. Dillon, Ontario Ministry of the Environment to the Global Lake and River Ice Phenology Database. The record holds the ice-out dates for Lake Opeongo, and an ice-in date for only eight of those winters, too few to draw on.

Ice out dates for 41 recorded springs between 1964 and 2004

Ice conditions

No public record reports the thickness or the condition of the ice on Lake Opeongo 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

Lake Opeongo contains 167 islands in the Ontario Hydro Network’s outline, four of them over 10 hectares and 102 under a tenth of a hectare. Opeongo Island, at 237 hectares, is larger than the next ten together, which cover 87.

Official names

Ontario’s geographic names register lists 10 official names on the water and its islands: 2 islands and three bays.

Bays 3

• Annie Bay
• Jones Bay
• Sproule Bay

Nearby lakes

• Canoe Lake30 km away
• Aylen Lake43 km away
• Bark Lake52 km away
• Little Kennisis Lake52 km away

All lakes

Questions about Lake Opeongo

• How big is Lake Opeongo?

  Its surface covers 59.3 square kilometers and it holds 167 islands. Of its 206 kilometers of shoreline, 152 kilometers is the mainland shore and 54 kilometers is the shore of the islands.

• What fish are in Lake Opeongo?

  Ontario’s aquatic resource records name 30 species, among them lake trout, smallmouth bass, lake whitefish, yellow perch and brook trout. The lake’s spawning, consumption and stocking records also name splake.