Bass Lake

Where Bass Lake is

Bass Lake lies in the County of Simcoe, within the Township of Oro-Medonte.

How deep is Bass Lake?

Bass Lake reaches a maximum recorded depth of 10.0 meters, determined from 39,075 soundings.

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.

Bass Lake has 2 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.

The longest record is held by site 6935/2 at Mid Lake, deep spot, sampled over 13 springs to 2018. Its long-term mean phosphorus concentration is 11.28 micrograms per litre, within the mesotrophic band, which runs from 10 to 20. The site’s 78 clarity readings give a median Secchi depth of 3.0 meters.

Water temperature

Ontario’s aquatic resource records class Bass Lake as a cool-water lake, with a mean depth of 3.5 meters against its maximum of 10.

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 Bass 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.

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

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 Bass Lake

Ontario’s aquatic resource records name 21 fish species in Bass Lake. The province classes the lake as cool water. The record took effect on 14 October 2010, and it compiles what field biologists had reported by then.

Nine of the 21 species in the province’s records

• Brook Trouttrout and whitefish
• Rainbow Trouttrout and whitefish
• Yellow Perchperch
• Smallmouth Basssunfish
• Largemouth Basssunfish
• Black Crappiesunfish
• Rock Basssunfish
• Pumpkinseedsunfish
• Brown Bullheadcatfish

Stocking history

Ontario’s stocking records for Bass Lake run from 1946 to 1974 and hold 36 releases. Smallmouth Bass account for most of the fish: 76,150 released in fourteen of the years between 1946 and 1963. The last recorded release was 4,500 rainbow trout yearlings in 1974.

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

Eating the fish

The 2025 Guide to Eating Ontario Fish carries consumption advice for six species taken from Bass Lake, tested for contaminants at a sampling location in Oro & Orillia Twps., Simcoe Co. 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 16

Bass Lake lies in Fisheries Management Zone 16. Ontario sets its fishing seasons and catch limits by zone. Zone 16 is the most southerly inland zone in the province and takes in all of southwestern Ontario, with Toronto, Mississauga, Hamilton, Kitchener-Waterloo and London. The province describes it as a zone of large river systems, with Lake Simcoe and Lake Couchiching its large lakes, carrying important recreational and tourism fisheries under high fishing 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 Bass Lake.

Bass Lake Ice Fishing

An ice hut on Bass Lake must be removed by March 15. Bass Lake lies in fisheries management zone 16, 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 16 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

Ice has been recorded on Bass Lake in twenty winters between 1973 and 1995. The median date of complete ice cover is December 3 and the median date of complete ice loss is April 17, a median season of 138 days.

The longest recorded season is 153 days in 1974-75, and the shortest is 119 days in 1982-83.

The record was contributed by W. R. Skinner, Environment Canada to the Global Lake and River Ice Phenology Database, and the ice was read at a weather station rather than from the middle of the lake. Observations were last contributed for 1995, and none have been added since.

Ice conditions

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

Nearby lakes

• Lake Couchiching13 km away
• Lake Simcoe23 km away
• Sparrow Lake25 km away
• Morrison Lake30 km away

All lakes

Questions about Bass Lake

• How deep is Bass Lake?

  Its maximum recorded depth is 10 meters.

• How big is Bass Lake?

  Its surface covers 5.5 square kilometers, with 11 kilometers of shoreline.

• What fish are in Bass Lake?

  Ontario’s aquatic resource records name 21 species, among them smallmouth bass, largemouth bass, yellow perch, black crappie and brook trout.

• Is the water clear?

  The one monitoring site with a phosphorus status is classified mesotrophic, the middle of the province’s three bands.