Lake Joseph

Where Lake Joseph is

Lake Joseph lies in the District Municipality of Muskoka and the District of Parry Sound, with shoreline in the Township of Muskoka Lakes and the Township of Seguin.

How deep is Lake Joseph?

Lake Joseph reaches a maximum recorded depth of 92.5 meters, determined from 152,057 soundings taken during Ontario’s 2003 survey.

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.

Lake Joseph Aerial Photography

Ontario photographs the province from the air on a rolling schedule.

The photograph below is from the SCOOP2023 collection, flown in 2023 and 2024.

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.

Lake Joseph has 12 Lake Partner monitoring sites. Two have reported phosphorus for the three or more years the province requires before a status is assigned. All are classified oligotrophic.

The longest record is held by site 2460/10 at Gordon Bay, deep spot, sampled over 9 springs to 2025. Its long-term mean phosphorus concentration is 4.47 micrograms per litre, within the oligotrophic band, which extends to 10. The site’s 6 clarity readings give a median Secchi depth of 5.65 meters.

Water temperature

Ontario’s aquatic resource records class Lake Joseph as a cold-water lake, with a mean depth of 26 meters against its maximum of 92.5.

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 26 meters places most of Lake Joseph’s volume in that cold layer, which is the condition lake trout and lake whitefish require.

No provincial monitoring station records water temperature on Lake Joseph. 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.

Satellite thermal imagery gives a surface reading on clear days: the Landsat sensors pass over Lake Joseph 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.

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 Lake Joseph

Ontario’s aquatic resource records name 34 fish species in Lake Joseph. 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. The province’s other records for the lake name two further species, rainbow trout and brook trout. They appear in the records below.

Fourteen of the 36 species in the province’s records

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

Spawning areas

Ontario maps 820 fish spawning records within the Lake Joseph outline, for six species, all of them mapped areas. Every record is recorded as verified and presently suitable, and none is classed as sensitive.

By number of records

By area mapped

• Smallmouth Bass700 areas4.0 ha
• Lake Trout106 areas14.0 ha
• Northern Pike8 areas18.3 ha
• Walleye3 areas0.8 ha
• Muskellunge2 areas1.9 ha
• Rainbow Smelt1 area0.1 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 Lake Joseph run from 1946 to 1975 and hold 44 releases. Walleye account for most of the fish: 5,225,000 released in six of the years between 1946 and 1958. The last recorded release was 2,500 rainbow trout yearlings in 1975.

The province’s current stocking programme, recorded from 2016, lists no release into Lake Joseph.

Eating the fish

The 2025 Guide to Eating Ontario Fish carries consumption advice for seven species taken from Lake Joseph, tested for contaminants at a sampling location in Medora Twp., Muskoka D.M. Each figure below is the most meals a month the guide advises for a fish of that length. The advice 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 15

Lake Joseph 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.

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. No waterbody exception names Lake Joseph.

Lake Joseph Ice Fishing

An ice hut on Lake Joseph must be removed by March 31. Lake Joseph 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 Lake Joseph. The province’s nearest long record covers eight lakes near Dorset, about 60 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.

Ice conditions

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

Getting on the water

Nine access marks are mapped on Lake Joseph: two boat launches, six marinas and one beach. Four are Ontario’s own records, three are from the Overture Places dataset and two are operator entries, and the list under the map says which is which. Boat launch is the province’s class for a ramp.

Islands and names

Lake Joseph contains 93 islands in the Ontario Hydro Network’s outline, fourteen of them over 10 hectares and 21 under a tenth of a hectare.

Official names

Ontario’s geographic names register lists 125 official names on the water and its islands: 86 islands, 28 bays, one shoal, one rock, one narrows and four points on islands. A further 46 named points stand on the mainland shore. The register records the origin of five names.

Bays 28

• Avon Bay
• Burnegie Bay
• Cox Bay
• Cumberland Bay
• Deer Bay
• Foot's Bay
• Gordon Bay
• Greens Bay
• Hamer Bay
• King Bay
• Ladies Bay
• Little Chiefs Bay
• McClelland Bay
• Orgills Bay
• Pickerel Bay
• Pinelands Bay
• Portage Bay
• Richards Bay
• Roberts Bay
• Seeley Bay
• Smith Bay
• Stanley Bay
• Stills Bay
• Townsends Bay
• Trout Bay
• Whalon Bay
• Woodroffe Bay
• Wrights Bay

Shoals and rocks 2

• Black Forest Shoal
• Ox Rock

Harbours, cuts and narrows 1

• Sandy Narrows

Points on the shore 46

• Ames Point
• Beley Point
• Black Rock Point
• Blair Point
• Blueberry Point
• Boulder Point
• Christies Point
• Clause Point
• Craig Point
• Craigie Lea Point
• Crossley Point
• Eagles Nest Point
• Elarton Point
• Flamarion Point
• Four Mile Point
• Glenavy Point
• Gospel Point
• Gregory Point
• Hamills Point
• Harwood Point
• Hemlock Point
• Idyl-Wild Point
• Jenckes Point
• Kerrs Point
• Kingsett Point
• Lash Point
• Lauder Point
• Macassa Point
• Maplehurst Point
• McArtiff Point
• Medora Point
• Moss Rock Point
• Norway Point
• Oak Bank Point
• Onnalinda Point
• Orgills Point
• Point Charles
• Proctors Point
• Riggs Point
• Rossmoyne Point
• Sandy Point
• Stevens Point
• Stormy Point
• Sunset Point
• Wildcat Point
• Worthington Point

Communities on the lake 11

• MacTier
• Foot's Bay
• Gordon Bay
• Hamer Bay
• Port Cockburn
• Glen Orchard
• Minett
• Port Sandfield
• Gregory
• Redwood
• Woodington

Nearby lakes

• Lake Rosseau8 km away
• Whitefish Lake14 km away
• Blackstone Lake15 km away
• Horseshoe Lake18 km away

All lakes

Questions about Lake Joseph

• How deep is Lake Joseph?

  Its maximum recorded depth is 92.5 meters, determined during Ontario’s 2003 survey.

• How big is Lake Joseph?

  Its surface covers 51.6 square kilometers and it holds 93 islands. Of its 212 kilometers of shoreline, 123 kilometers is the mainland shore and 89 kilometers is the shore of the islands.

• What fish are in Lake Joseph?

  Ontario’s aquatic resource records name 34 species, among them lake trout, walleye, smallmouth bass, largemouth bass, northern pike and muskellunge. The lake’s spawning, consumption and stocking records also name rainbow trout and brook trout.

• Is the water clear?

  All two monitoring sites with a phosphorus status are classified oligotrophic, the clearest of the province’s three bands.

• Is there a public boat launch?

  Records mark two boat launches, six marinas and one beach on Lake Joseph.