Parry Sound District, Ontario

Blackstone Lake

Nine islands and a deepest charted contour of 57.9 meters, from the province's 1969 survey, in the Township of the Archipelago. Lake trout water, stocked by the province five times between 2017 and 2025.

Surface: 5.1 km²
Shoreline: 34 km30 mainland + 4 islands
Islands: 9
Charted depth: 57.9 m
Depth contours: 23

All figures are derived from Ontario’s survey records.

Where Blackstone Lake is

Blackstone Lake lies in the District of Parry Sound, within the Township of the Archipelago.

How deep is Blackstone Lake?

The deepest mapped contour on Blackstone Lake is 57.9 meters, and the water within that boundary descends even farther. Ontario’s bathymetry record holds 23 depth contours for Blackstone Lake.

The deepest charted contour on Blackstone Lake, 57.9 meters, from the survey of 9 July 1969. The circle marks the centre of that contour, and the water within it is deeper. The survey’s twenty-three depth contours are drawn where the province published them, and along the outline where the survey placed them beyond it. Outline from the Ontario Hydro Network. Each contour is labelled with its depth in meters; zoom in where they run close.

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 a water sample each spring for phosphorus analysis and measure water clarity through the summer with a Secchi disk.

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 spring phosphorus. Below 10 micrograms per litre is oligotrophic: clear water and low algae. From 10 to 20 is mesotrophic: moderately productive water, with more algae and weed growth than an oligotrophic lake but rarely a bloom. Above 20 is eutrophic: nutrient-rich water, prone to algal blooms and low oxygen at depth.

A Secchi disk is a 20 centimeter 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.

Blackstone Lake has 9 Lake Partner monitoring sites. One of them has reported phosphorus for the three or more years the province requires before a status is assigned, and is classified oligotrophic.

Lake Partner sites on Blackstone Lake with a quotable phosphorus record
Site	Location	Years	Last sampled	Classification
461/1	Mid Lake, deep spot	19	2025	oligotrophic

The longest record is held by site 461/1 at Mid Lake, deep spot, sampled over 19 springs to 2025. Its long-term mean phosphorus concentration is 7.68 micrograms per litre, within the oligotrophic band, which extends to 10. The site’s 113 clarity readings give a median Secchi depth of 4.5 meters.

Median Secchi depth by year at site 461/1, surface at the top. The thin line through each bar spans the shallowest and deepest reading that year, and the row beneath the years gives the number of readings. Years without readings are blank.

Water temperature

Ontario’s aquatic resource records class Blackstone Lake as a cold-water lake, with a mean depth of 20 meters against its maximum of 57.9.

A deep lake separates into layers through the summer. Sunlight and wind warm and mix the upper few meters, and beneath a band of rapid cooling, the thermocline, the water stays cold through the whole season. A mean depth of 20 meters places most of Blackstone Lake’s volume in that cold layer, which is the condition lake trout and lake whitefish require.

No provincial monitoring station records water temperature on Blackstone Lake. 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, by half-month, on eight research lakes near Dorset, 1976 to 2025. The band holds the middle 80% of the 5,240 readings taken at one meter; the line is the median. The warmest tenth of years lie above the band and the coolest tenth below it.

Satellite thermal imagery gives a surface reading on clear days: the Landsat sensors pass over Blackstone Lake every eight days at a resolution of 100 meters. In the province’s record the surface reading and the one meter reading agree to within half a degree nine times in ten in summer.

The water a few meters down is colder than any figure on this chart, in every month of the year.

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.

February, under ice
May
June
July
August
September
October

Temperature against depth on Harp Lake, near Dorset, as the median of every reading at that depth in that month, 1976 to 2025. Surface at the top. The thermocline is the bend in each line.

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.

Fish in Blackstone Lake

Ontario’s aquatic resource records name 21 fish species in Blackstone Lake. The province classes the lake as cold water. The record took effect on 21 December 2016, and it compiles what field biologists had reported by then.

Thirteen of the 21 species in the province’s records

Lake Trouttrout and whitefish
Ciscotrout and whitefish
Northern Pikepike
Muskellungepike
Walleyeperch
Yellow Perchperch
Smallmouth Basssunfish
Largemouth Basssunfish
Black Crappiesunfish
Rock Basssunfish
Pumpkinseedsunfish
Burbotcod
Brown Bullheadcatfish

The other eight species in the province’s records
Family	Species
Perch	logperch
Sucker	white sucker
Smelt	rainbow smelt
Minnow	blacknose shiner, bluntnose minnow, common shiner, emerald shiner, golden shiner

Spawning areas

Ontario maps 38 fish spawning records within the Blackstone Lake outline: 38 sunfish family spawning areas covering 4.18 hectares. Every record is recorded as verified and presently suitable, and none is classed as sensitive.

By number of records

By area mapped

Sunfish family38 areas4.2 ha

Spawning records mapped by the province within the Blackstone Lake outline. A record under 100 square meters is drawn as a dot; a spawning area is drawn as the outline mapped. One colour per species, the same as the bars and the list above.

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 Blackstone Lake run from 1946 to 2015 and hold 70 releases. Walleye account for most of the fish: 5,233,928 released in fourteen of the years between 1946 and 2006. The last recorded release was 3,000 lake trout yearlings in 2015.

Fish released into Blackstone Lake, 1946 to 2015
Species	Years	Years with a release	Fish released
Walleye	1946 to 2006	14	5,233,928
Lake Trout	1956 to 2015	32	117,343
Muskellunge	1953 to 1962	8	77,250
Smallmouth Bass	1946 to 1954	5	11,225

The province’s current stocking programme, recorded from 2017, lists 11,000 lake trout released into Blackstone Lake between 2017 and 2025.

Fisheries Management Zone 15

Blackstone Lake lies in Fisheries Management Zone 15. Ontario sets its fishing seasons and catch limits by zone. Zone 15 covers central Ontario from Georgian Bay to the Ottawa River, bounded to the north by the Pickerel River, Highway 522 and the northern edge of Algonquin Park. It takes in Parry Sound, Huntsville, Bracebridge, Bancroft, Pembroke and Renfrew, and the whole of Algonquin Provincial Park. 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.

Zone 15 seasons and limits, 2026
Species	Open season	Sport licence	Conservation licence
Brook Trout	Jan. 1 – Sept. 30	5	2
Brown Trout	Open all year	5	2
Channel Catfish	Open all year	12	6
Crappie	Open all year	30	10
Lake Trout	Jan. 1 – Sept. 30	2	1
Lake Whitefish	Open all year	12	6
Largemouth and Smallmouth Bass or any combination	4th Sat. in June – Nov. 30	6	2
Muskellunge	1st Sat. in June – Dec. 15	1, must be greater than 91 cm (36 in.)	0
Northern Pike	Jan. 1 – Mar. 31 & 3rd Sat. in May – Dec. 31	6	2
Pacific Salmon	Open all year	5	2
Rainbow Trout	Open all year	5	2
Splake	Open all year	5	2
Sunfish	Open all year	50	25
Walleye and Sauger or any combination	Jan. 1 – Mar. 15 & 3rd Sat. in May – Dec. 31	4, not more than 1 greater than 46 cm (18.1 in.)	2, not more than 1 greater than 46 cm (18.1 in.)
Yellow Perch	Open all year	50	25

The figures are the number of fish an angler may catch and keep in a day and have in possession, under a sport fishing licence and under a conservation licence. The rows are the whole zone’s, and they apply to every lake in it.

Exceptions for Blackstone Lake itself, 2026
Species	Open season	Sport licence	Conservation licence
Lake Trout	Open all year	Zone-wide	Zone-wide

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

Fish sanctuaries recorded for Blackstone Lake
Where	Closed
Blackstone Lake and Creek – Conger Twp., Lots 12, 13, 14 in Conc. XII	No fishing from Apr. 1 – Fri. before 3rd Sat. in May

Blackstone Lake Ice Fishing

An ice hut on Blackstone Lake must be removed by March 31. Blackstone Lake lies in fisheries management zone 15, one of the twenty zones Ontario sets its fishing rules by, and one removal date applies across the whole zone.

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 zone 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.

When the ice comes and goes

No ice record is kept on Blackstone Lake. The province’s nearest long record covers eight lakes near Dorset, about 74 kilometers away. It holds a date for every winter since 1975, observed by eye and from cameras set on the shore.

On those eight lakes the median date of complete ice cover is December 7 and the median date of complete ice loss is April 20, a median season of 134 days.

The date the ice forms has moved later through the record: a November 26 average across 1971 to 1980, and December 11 across 2011 to 2020. The date it leaves has moved by less than a day each decade over the same period. The two charts below are drawn to one scale of 26 days, so they can be read against each other.

Mean date of complete ice cover on eight lakes near Dorset, by decade, with the number of recorded winters beneath. Ontario Ministry of the Environment, Conservation and Parks, Dorset Environmental Science Centre.

Mean date of complete ice loss on the same eight lakes, by decade, drawn to the same scale of days as the chart above. Ontario Ministry of the Environment, Conservation and Parks, Dorset Environmental Science Centre.

Ice conditions

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

Islands and names

Blackstone Lake contains 9 islands in the Ontario Hydro Network’s outline, zero of them over 10 hectares and one under a tenth of a hectare.

The nine largest islands, numbered to the table. Areas are measured on the province’s outline.

The nine largest islands
	Island	Hectares
1	unnamed	3.1
2	unnamed	1.7
3	Kelley Island	1.4
4	Oriole Island	1.2
5	Acadia Island	1.1
6	Myrtle Island	0.9
7	unnamed	0.4
8	Chicadee Island	0.2
9	unnamed	0.0

Official names

Ontario’s geographic names register lists 8 official names on the water and its islands: 5 islands, two bays and one rock.

Bays 2

Lawson Bay
McRobert Bay

Shoals and rocks 1

Black Rock

Nearby lakes

Crane Lake4 km away
Otter Lake7 km away
Horseshoe Lake9 km away
Healey Lake9 km away

All lakes

Questions about Blackstone Lake

How deep is Blackstone Lake?
Its deepest charted contour is 57.9 meters, and the water within it is deeper.
How big is Blackstone Lake?
Its surface covers 5.1 square kilometers and it holds 9 islands. Of its 34 kilometers of shoreline, 30 kilometers is the mainland shore and 4 kilometers is the shore of the islands.
What fish are in Blackstone Lake?
Ontario’s aquatic resource records name 21 species, among them lake trout, walleye, smallmouth bass, largemouth bass, northern pike and muskellunge.
Is the water clear?
The one monitoring site with a phosphorus status is classified oligotrophic, the clearest of the province’s three bands.

A print of Blackstone Lake

Blackstone Lake has not yet been drawn as a print. The lakes drawn so far are on the lake maps page, and a print of Blackstone Lake can be requested by email; whether it can be drawn is confirmed before any payment.

Ask about a Blackstone Lake print

Looking at a property on Blackstone Lake?

Depth and water quality are two records out of many. Our Rural & Cottage Buyer’s Report gathers what the public record holds about one specific address: shore road allowance, road access, wells, flood mapping, Crown land, wetlands and more, read and checked by a person before it is sent.

See what is in the report

What these figures do and do not say

Depth: A depth reading is the distance from the water surface on the day of survey to the lake bottom. Lake levels vary through the season and between years. The depth figure above is the deepest contour charted and is a minimum; the depth within it was not recorded. The figures for Blackstone Lake are read from the province’s bathymetry records within the Ontario Hydro Network’s outline of the lake: the deepest figure is the deepest record inside that outline, and the count is every record inside it.
Shoreline and surface: The shoreline figure is the length of the mainland shore and of every island shore added together, measured on the Ontario Hydro Network’s outline of the lake. The surface figure is the area of water inside that outline, less the area of its islands. The provincial outline is mapped to within a few meters of the shore, and a shoreline measured from a coarser map comes out shorter, which is why a figure published elsewhere is often lower.
Survey coverage: Not every survey covered every arm of a lake, and the province’s index does not always record where a survey ended.
Water quality: Each figure belongs to a single monitoring site and not to the lake as a whole. A bay receiving a creek can read differently from open water half a kilometer away. Sites are matched to Blackstone Lake by name in the province’s records.
Nearby lakes: Distances are measured between lake centres.
Islands and names: Islands are counted and measured on the Ontario Hydro Network outline; names are the register’s, placed by its own coordinate. The register names islands the outline draws as part of a larger one, and the outline holds islands the register has not named, so the two counts differ. The outline carries some lakes across marsh, so a gap in the marsh is drawn as land, and every such gap is included in the island count. Where the register has not named one and it lies mostly inside a wetland in the province’s Wetland With Significance dataset, the page names the wetland and the table of largest islands leaves it out. Wetland boundaries are mapped at their own scale and can cover a small island whole.
Depth contours: Each contour is drawn where the survey placed it, at the survey’s own positional accuracy. The survey carries its own shoreline, which differs from the Ontario Hydro Network’s outline, so a contour near the shore can run to or past the outline. Such a stretch is drawn along the outline, as a drawing convention, and is not the survey’s line there. The contour count in the stat band is the province’s, and it includes the survey’s own shoreline contour, one ring around the mainland and one around each charted island, which the map leaves off; the map’s small print gives the split.
Location: Municipal boundaries are read from the province’s records as published and can lag a boundary change.
Temperature: The temperature band is the province’s record on eight research lakes near Dorset and is a range for the half-month. It is never a reading from Blackstone Lake, and a larger and deeper lake can warm later in spring and cool later in autumn than the lakes in the record. A satellite reading measures the surface on the day of the pass. Water below the surface layer is colder than any figure on this page, and cold-water shock can occur in water below about 15 degrees.
Fish: Ontario’s fish records are compilations of existing knowledge from field biologists and do not represent exhaustive inventories. A species that is not listed was not ruled out. The species list carries one date for the whole record and none for any species.
Spawning areas: A spawning area is drawn where the province mapped it, at the province’s stated accuracy, and the record says nothing about how many fish use it in a given year. A nest record is one nest seen on one day; a count of nests is not a count of fish, and a count of records is not a comparison between species. Whether a given piece of work needs an authorization is a determination made by Fisheries and Oceans Canada on the work itself.
Stocking: A stocking record is a release on a date. It says nothing about how many fish survived or about the population in the lake today.
Fishing rules: Seasons and limits are the zone’s, for the year of the dataset the page was built from, and a licence’s own conditions and any waterbody exception apply over them. The province’s regulations summary is the authority.
Ice dates: A break-up date is the day a lake was recorded as no longer completely covered by ice, and a freeze date is the day it was recorded as completely covered. Both are read from the shore. A winter carrying no date is a winter nobody recorded, and not a winter without ice. Each Dorset figure is the average of the eight lakes and is not a record of Blackstone Lake. All eight lie within 10 to 30 kilometers of Dorset. They are smaller and shallower than most of the lakes on these pages, and a smaller lake freezes sooner.
Ice hut rules: Removal dates and registration rules are set by fisheries management zone and change from time to time. The dates here were read from the province in September 2026. The province’s own fishing regulations are the authority.

Where these figures come from

Depth, shoreline, islands and named places: Ontario Ministry of Natural Resources bathymetry and the Ontario Hydro Network, © King’s Printer for Ontario, Open Government Licence – Ontario.
Phosphorus and water clarity: Ontario Lake Partner Program, Ministry of the Environment, Conservation and Parks, Open Government Licence – Ontario. Extract built 2026-08-09.
Aerial photography: Geospatial Ontario imagery, Open Government Licence – Ontario, released collections only.
Official names: Geographic Names Ontario, Ministry of Natural Resources, Open Government Licence – Ontario. Marinas: Overture Maps Foundation places data, CDLA-Permissive 2.0.
Lake outline and municipal boundaries: Ontario Hydro Network and Ontario municipal boundary records, Ministry of Natural Resources, Open Government Licence – Ontario.
Water temperature: Inland Lakes and Streams, Physical Conditions, Dorset Environmental Science Centre, Ministry of the Environment, Conservation and Parks, Open Government Licence – Ontario, 1976 to 2025. Surface temperature: Landsat 8 and 9, U.S. Geological Survey, public domain.
Fish species and thermal regime: Ontario Aquatic Resource Area records. Spawning areas: Ontario Fish Activity Area records. Both Ministry of Natural Resources, Open Government Licence – Ontario.
Stocking: Historical Fish Stocking Data and Fish Stocking Data for Recreational Purposes, Ministry of Natural Resources, Open Government Licence – Ontario.
Seasons and limits: Ontario recreational fishing regulations data, Ministry of Natural Resources, Open Government Licence – Ontario.
Fish plates: Duane Raver, U.S. Fish and Wildlife Service; Ellen Edmonson and Hugh Chrisp, New York State Conservation Department; Timothy Knepp, U.S. Fish and Wildlife Service; U.S. Fish and Wildlife Service. All public domain.
Ice dates near Dorset: Inland Lakes and Streams, Physical Conditions, Dorset Environmental Science Centre, Ministry of the Environment, Conservation and Parks, Open Government Licence – Ontario, 1974 to 2022.
Ice hut removal dates and registration: Ontario fishing regulations, read September 2026.