Leeds and Grenville, Ontario

Red Horse Lake

Three square kilometers of water in Leeds and the Thousand Islands, with 12 islands and 30 kilometers of shoreline, charted to 36.6 meters across 22 depth lines. Two northern pike spawning areas are mapped, and lake trout and splake stocking continues in the current record.

Surface: 3.0 km²
Shoreline: 30 km28 mainland + 2 islands
Islands: 12
Charted depth: 36.6 m
Depth contours: 22

All figures are derived from Ontario’s survey records.

Where Red Horse Lake is

Red Horse Lake lies in the United Counties of Leeds and Grenville, within the Township of Leeds and the Thousand Islands.

How deep is Red Horse Lake?

The deepest mapped contour on Red Horse Lake is 36.6 meters, and the water within that boundary descends even farther. Ontario’s bathymetry record holds 22 depth contours for Red Horse Lake.

The deepest charted contour on Red Horse Lake, 36.6 meters. The circle marks the centre of that contour, and the water within it is deeper. Two contours reach this depth; the largest is marked. The survey’s twenty-two 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.

Red Horse Lake has 7 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 mesotrophic.

Lake Partner sites on Red Horse Lake with a quotable phosphorus record
Site	Location	Years	Last sampled	Classification
4575/1	W Basin-S Centre Is.	14	2015	mesotrophic

The longest record is held by site 4575/1 at W Basin-S Centre Is., sampled over 14 springs to 2015. Its long-term mean phosphorus concentration is 16.7 micrograms per litre, within the mesotrophic band, which runs from 10 to 20. The site’s 151 clarity readings give a median Secchi depth of 4.0 meters.

Median Secchi depth by year at site 4575/1, 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.

Fish in Red Horse Lake

Ontario’s aquatic resource records name 19 fish species in Red Horse Lake. The record took effect on 27 October 2010, and it compiles what field biologists had reported by then. The province’s other records for the lake name one further species, splake. It appears in the records below.

Fourteen of the twenty species in the province’s records

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

The other six species in the province’s records
Family	Species
Trout and whitefish	splake
Sucker	white sucker
Minnow	blackchin shiner, bluntnose minnow
Eel	american eel
Killifish	banded killifish

Spawning areas

Ontario maps 3 fish spawning records within the Red Horse Lake outline, for two species. One is records of under 100 square meters each, and the other two are mapped areas.

By number of records

By area mapped

Northern Pike2 areas1.3 ha
Lake Trout1 records100 m²

Spawning records mapped by the province within the Red Horse 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 Red Horse Lake run from 1946 to 2015 and hold 93 releases. Lake Trout account for most of the fish: 241,733 released in 47 of the years between 1946 and 2015. The last recorded release was 5,000 lake trout yearlings in 2015.

Fish released into Red Horse Lake, 1946 to 2015
Species	Years	Years with a release	Fish released
Lake Trout	1946 to 2015	47	241,733
Walleye	1952 to 1952	1	100,000
Smallmouth Bass	1947 to 1978	21	43,497
Largemouth Bass	1954 to 1978	19	42,398
Splake	2014 to 2014	1	10,400

The province’s current stocking programme, recorded from 2016, lists 60,773 lake trout released into Red Horse Lake between 2016 and 2025.

Eating the fish

The 2025 Guide to Eating Ontario Fish carries consumption advice for four species taken from Red Horse Lake, tested for contaminants at a sampling location in Leeds & Lansdowne Twps. 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

Lake Trout Mercury, PCB
Length, cm	30 to 35	35 to 40	40 to 45	45 to 50	50 to 55	55 to 60	60 to 65	65 to 70
General population	12	12	12	12	12	8	8	8
Sensitive population	8	4	4	4	4	4	4	0

Northern Pike Mercury
Length, cm	55 to 60	60 to 65	65 to 70	70 to 75	over 75
General population	8	4	4	4	2
Sensitive population	0	0	0	0	0

Largemouth Bass Mercury
Length, cm	35 to 40	40 to 45
General population	4	4
Sensitive population	0	0

Yellow Perch Mercury
Length, cm	20 to 25	25 to 30
General population	16	8
Sensitive population	8	4

Fisheries Management Zone 18

Red Horse Lake lies in Fisheries Management Zone 18. Ontario sets its fishing seasons and catch limits by zone.

Zone 18 seasons and limits, 2026
Species	Open season	Sport licence	Conservation licence
Brook Trout	Open all year	5	2
Brown Trout	Open all year	5	2
Channel Catfish	Open all year	12	6
Crappie	Open all year	30	10
Lake Trout	4th Sat. in May – Sept. 8	2	1
Lake Whitefish	Open all year	12	6
Largemouth and Smallmouth Bass or any combination	3rd Sat. in June – Dec. 15	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 & 2nd 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	300, only 30 may be greater than 18 cm (7.1 in.)	15
Walleye and Sauger or any combination	Jan. 1 – Mar. 1 & 2nd Sat. in May – Dec. 31	4, must be between 40 – 50 cm (15.7 – 19.7 in.)	2, must be between 40 – 50 cm (15.7 – 19.7 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 Red Horse 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.

Red Horse Lake Ice Fishing

An ice hut on Red Horse Lake must be removed by March 15. Red Horse Lake lies in fisheries management zone 18, 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 18 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 Red Horse Lake on any given day. Ontario publishes ice safety guidance for anyone going out on the ice, at ontario.ca.

Islands and names

Red Horse Lake contains 12 islands in the Ontario Hydro Network’s outline, zero of them over 10 hectares and five under a tenth of a hectare. Five of them lie inside wetlands mapped in the province’s Wetland With Significance dataset.

The seven largest islands outside a mapped wetland, numbered to the table. Areas are measured on the province’s outline.

The seven largest islands outside a mapped wetland
	Island	Hectares
1	Twin Islands	0.5
2	Porcupine Island	0.4
3	Daly Island	0.4
4	Indian Island	0.3
5	Hedgehog Island	0.3
6	unnamed	0.1
7	unnamed	0.1

Official names

Ontario’s geographic names register lists 9 official names on the water and its islands: 5 islands and three bays. A further 1 named point stands on the mainland shore.

Bays 3

Cold Spring Bay
Cronin Bay
Washburn Bay

Points on the shore 1

Long Point

Nearby lakes

Charleston Lake5 km away
Upper Beverley Lake9 km away
Sand Lake15 km away
Newboro Lake22 km away

All lakes

Questions about Red Horse Lake

How deep is Red Horse Lake?
Its deepest charted contour is 36.6 meters, and the water within it is deeper.
How big is Red Horse Lake?
Its surface covers 3.0 square kilometers and it holds 12 islands. Of its 30 kilometers of shoreline, 28 kilometers is the mainland shore and 2 kilometers is the shore of the islands.
What fish are in Red Horse Lake?
Ontario’s aquatic resource records name nineteen species, among them lake trout, walleye, smallmouth bass, largemouth bass, northern pike and lake whitefish. The lake’s spawning, consumption and stocking records also name splake.
Is the water clear?
The one monitoring site with a phosphorus status is classified mesotrophic, the middle of the province’s three bands.

A print of Red Horse Lake

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

Ask about a Red Horse Lake print

Looking at a property on Red Horse 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 Red Horse 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 Red Horse 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.
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.
Eating advice: The guide’s advice is for fish taken from the lake at the tested location and applies to the size classes tested. The province’s guide is the authority and is updated each year.
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 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.
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.
Consumption advice: Guide to Eating Ontario Fish advisory database, 2025 edition, Ministry of the Environment, Conservation and Parks, 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; Timothy Knepp, U.S. Fish and Wildlife Service; U.S. Fish and Wildlife Service. All public domain.
Ice hut removal dates and registration: Ontario fishing regulations, read September 2026.