Lake whitefish (Coregonus clupeaformis) in Lake Simcoe COSEWIC assessment and status report: chapter 2

Executive Summary

Lake Whitefish
Coregonus clupeaformis
(Lake Simcoe population)

Species Information

Lake whitefish are elongate in form, the greatest body depth occurring at the front of dorsal fin. The mouth is inferior,

being distinctly overhung by the snout. Overall colour is silvery and fins are usually clear or lightly pigmented in Great Lakes populations; the fins of more northerly populations are often darker and are usually black tipped. Scales are large and cycloid, numbering 70-97 in the lateral line. Breeding males develop nuptial tubercles on at least 3 rows of scales above the lateral line and on 6 rows below. Genetic, morphological and meristic differences suggest some difference from neighbouring populations; however, this evidence is inconclusive and does not support delineation of this population as a Designatable Unit.

Distribution

The lake whitefish is widely distributed throughout Canada and the northern United States. The Lake Simcoe population is a distinct stock found in Lake Simcoe, Ontario (44º25’N, 79º20’W). It has been separated from other whitefish stocks in the Great Lakes Basin for an estimated 7,000 to 10,000 years.

Habitat

In Lake Simcoe, adult lake whitefish are associated with the lake bottom and widely distributed throughout the lake, including the open basin, Cook Bay, and Kempenfelt Bay during the winter and spring.  As water temperature increases in the late spring, Lake Simcoe lake whitefish move to the cool deep waters of the lake to depths of 20 to 40 m. Lake whitefish first move to spawning shoals in October and remain until early December. Lake whitefish spawn over shoals (1 to 3 m of depth) consisting of boulder, cobble and gravel.

Biology

Lake Simcoe lake whitefish abundance declined dramatically in the 1970s, largely as a result of recruitment failure. Annual stocking of lake whitefish began in 1982 and stocked fish now constitute the majority of the Lake Simcoe lake whitefish population.

However, wild lake whitefish continue to be present, three decades after recruitment problems began.

Lake whitefish diet shifts from a dominance of plankton to benthic organisms during their first summer. Adult lake whitefish are benthivores and their diet consists primarily of insect larvae, molluscs and amphipods.

Population Sizes and Trends

Generally, catches of Lake Simcoe lake whitefish were high during the 1960s and decreased sharply by the early 1970s. Since then, catch has remained relatively low compared to catches during the 1960s, but has increased somewhat as a result of the annual stocking of hatchery-reared fish. Wild lake whitefish continue to contribute to the recreational fisheries as well as to trap net catches on spawning shoals during the fall. However, catch rates of wild fish during the winter fishery have decreased since 1986, and catch has decreased during the fall index trap-netting program since 1992.

Currently, the Lake Simcoe lake whitefish population is made up largely of hatchery-reared fish along with a smaller population of wild fish. Catch rates of wild fish are extremely low compared with data from the 1960s. Evidence suggests that currently, the wild lake whitefish population is made up mostly of old individuals that were the result of successful recruitment in the 1960s. While it is possible that some successful natural recruitment to maturity still takes place, the magnitude of such events appears to be small and has little bearing on the size and age structure of the population.

Limiting Factors and Threats

The decline of lake whitefish, lake trout (Salvelinus namaycush) and cisco (C. artedi) has been attributed to nutrient loading and accelerated eutrophication and its impacts on spawning and hypolimnetic habitat in Lake Simcoe. More recently, declines in the abundance of burbot (Lota lota) have also been observed.

The introduction of exotic species may also have played a role in the Lake Simcoe lake whitefish population decline and could possibly affect their recovery. Rainbow smelt (Osmerus mordax) were first documented in Lake Simcoe in 1961 and by the early 1970s had become very well established. The timing of rainbow smelt expansion in the late 1960s coincides very closely with recruitment failure of lake whitefish. Zebra mussels (Dreissena polymorpha) and spiny waterflea (Bythotrephes sp.) were first observed in Lake Simcoe in 1992 and 1994, respectively. There is no evidence that these species have negatively affected growth or survival of hatchery-reared Lake Simcoe lake whitefish. However, the effect, if any, that these species would have on juvenile lake whitefish less than six months of age is unknown.

Special Significance of the Species

Along with other cold-water fish species in Lake Simcoe, the decline in lake whitefish abundance in the lake has indicated deteriorating habitat quality. As indicators of habitat quality, lake whitefish fulfill an important ecological role and should be protected. Successful rehabilitation of lake whitefish habitat could also result in rehabilitation of other cold-water species in Lake Simcoe.

The Lake Simcoe lake whitefish remains the species most targeted by recreational anglers. This fishery increases tourism to the area and provides an influx of money to the local economy, especially important to nearby communities in the winter. The lake whitefish fishery is also the only fishery accessible to the large human population of southern Ontario on a daily basis.

Existing Protection or Other Status Designations

The federal Fisheries Act serves as the primary legislation for the protection of fish and fish habitat in Canada.

To maintain the genetic strain of the Lake Simcoe lake whitefish, approximately 140,000 lake whitefish are stocked into Lake Simcoe annually. The status of the whitefish stock is monitored routinely by the Ontario Ministry of Natural Resources (OMNR) through the Lake Simcoe Fisheries Assessment Unit (LSFAU) programs.

The Lake Simcoe Environmental Strategy (LSEMS) was created to improve and protect the health of the Lake Simcoe watershed ecosystem and improve associated recreational opportunities by restoring a self-ustaining coldwater fishery, improving water quality, reducing phosphorus loads to Lake Simcoe and protecting natural heritage features and functions.

COSEWIC History

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 5, 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.

COSEWIC Mandate

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 Membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal agencies (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 members and the co-chairs of the species specialist and the Aboriginal Traditional Knowledge subcommittees. The Committee meets to consider status reports on candidate species.

Definitions (November 2004)

Species
Any indigenous species, subspecies, variety, or geographically defined population of wild fauna and flora.

Extinct (X)
A species that no longer exists.

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

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

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

Special Concern (SC) Footnote1
A species of special concern because of characteristics that make it particularly sensitive to human activities or natural events.

Not at Risk (NAR) Footnote2
A species that has been evaluated and found to be not at risk.

Data Deficient (DD) Footnote3
A species for which there is insufficient scientific information to support status designation.

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.

Canadian Wildlife Service

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

 

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