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COSEWIC assessment and status report on the Atlantic Salmon (Lake Ontario population) in Canada

Executive Summary

Atlantic Salmon

Salmo Salar

Lake Ontario Population


Species information 

The Atlantic salmon (Salmo salar) belongs to the family Salmonidae that includes Atlantic and Pacific salmon, trout, charr, grayling and whitefishes.  Adult Atlantic salmon that have been out to sea have trout-like bodies with a blue-green back and silvery sides.  The freshwater adults once populating Lake Ontario were reportedly smaller and darker than anadromous strains.  This report is concerned with the Lake Ontario population (COSEWIC Designatable Unit).



Anadromous Atlantic salmon once occurred in every country with rivers flowing into the North Atlantic Ocean and Baltic Sea.  In Canada, nearly every suitable coastal stream within Nova Scotia, New Brunswick, Prince Edward Island, Quebec, Labrador, and Newfoundland supported a spawning run of anadromous salmon.  In addition, many inland lakes had freshwater populations that did not migrate to the ocean.  Atlantic salmon populations have declined in number throughout much of their global range, as well as in Canada, and self-sustaining populations are no longer found west of Montréal. The Lake Ontario population ceased to exist over 100 years ago.



Streams suitable for Atlantic salmon juveniles and adult spawning are characterized by clean water seldom rising above 25°C and naturally graded and stable beds with stony bottoms comprised of particles varying in size from coarse sand and gravel to large boulders. Anadromous Atlantic salmon utilize estuaries and continental margins as well as open seas for growth to the adult stage.  Little is known about the specific stream or lake habitat required by the extinct Lake Ontario Atlantic salmon.  Usage of streams was probably similar to that for other populations in eastern Canada, and Lake Ontario, because of its large size, likely sustained the adult stage in a manner somewhat similar to that of an ocean environment.



Atlantic salmon have a complex life history typically described as progressing from egg to alevin to fry to parr to smolt to grilse to adult to kelt.  The Lake Ontario Atlantic salmon, unlike those in eastern Canada, probably did not migrate to the Atlantic Ocean but instead completed its life cycle within the Lake Ontario watershed, with egg through parr stage in rivers and smolt through adult and kelt stages within the lake.  The life history of Lake Ontario Atlantic salmon was probably similar to that of the species in general, although local adaptations such as in run timing are known.


Population sizes and trends

The Lake Ontario Atlantic salmon is extinct.  At one time, Atlantic salmon were so common in Lake Ontario and its tributaries that catches were measured in barrels of fish rather than in numbers of individual fish.  The population began to decline by the mid-1800s and continued to decline with various hatchery stocking activities, which began in 1866.  The last known Atlantic salmon was removed from the Lake Ontario basin before 1900, by anglers.  Today, the Lake Ontario ecosystem contains apparently suitable habitat for Atlantic salmon; however, attempts at stocking non-native populations have continued to be unsuccessful in establishing reproducing populations. 


Limiting factors and threats

Lake Ontario Atlantic salmon habitat was degraded by timbering, agriculture, and mills and dams across rivers that prevented access to spawning grounds.  Adult Atlantic salmon were also captured as food fish, and harvested in large numbers in a commercial fishery.  Lake Ontario fish communities and the aquatic environment have continued to change dramatically over time; presenting new challenges to the introduction of non-native Atlantic salmon.  There have been many stocking efforts, but there are no self-reproducing Atlantic salmon in Lake Ontario.


Special significance of the species 

Atlantic salmon are said to have encouraged the territorial expansion by Europeans into the interior of Canada.  The "king of fish" was valued by aboriginals, provided food for natives and settlers alike, and enabled the creation of a fishery employing thousands of people.  The Atlantic salmon was an important species ecologically, functioning in the movement of nutrients from the lake into its tributaries, and as a top predator in both the rivers and the lake.  Several recent watershed fisheries management plans have identified the public's interest in restoring naturally sustaining populations of Atlantic salmon.


Existing protection or other status designations 

Due to its vast range and collectively large population, the Atlantic salmon has been given a global rank by the Nature Conservancy of G5 (demonstrably widespread, abundant and secure), and a national rank of N4 (apparently secure).  At the individual provincial and state levels, however, the designations range from "presumed extirpated" in Ontario, to "secure" in Quebec.  Inner Bay of Fundy Atlantic salmon are currently listed as endangered by Canada’s Species at Risk Act (SARA), and most neighbouring US populations of Atlantic salmon are listed as endangered (US Endangered Species Act).


The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list.  On June 5th 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.



The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.



COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species. 




Wildlife Species: A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and it is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X): A wildlife species that no longer exists.

Extirpated (XT): A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E): A wildlife species facing imminent extirpation or extinction.

Threatened (T): A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)*: A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)**: A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)***: A category that applies when the available information is insufficient (a) to resolve a species' eligibility for assessment or (b) to permit an assessment of the species' risk of extinction.

*       Formerly described as "Vulnerable" from 1990 to 1999, or "Rare" prior to 1990.
**     Formerly described as "Not In Any Category", or "No Designation Required."
***   Formerly described as "Indeterminate" from 1994 to 1999 or "ISIBD" (insufficient scientific information on which to base a designation) prior to 1994. Definition of the (DD) category revised in 2006.


Environment                         Environnement
Canada                                Canada

Canadian Wildlife                 Service canadien
Service                                de la faune

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.