Misty Lake sticklebacks COSEWIC asessment and status report: chapter 2

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Executive Summary

Species information

The Misty Lake sticklebacks, a highly divergent parapatric lake-stream pair of threespine stickleback, are found in a single small lake on Vancouver Island, British Columbia (BC). Similar parapatric lake-stream pairs have also been well documented in two other systems in BC, Mayer and Drizzle lakes on Graham Island (Queen Charlotte Islands). These pairs live in contact (parapatry) without a significant amount of overlap or interbreeding. Differences in body shape are believed to be adaptations to the different feeding strategies used by each member of the species pair. Genetic evidence suggests that each of the three highly divergent lake-stream pairs has evolved separately through parallel evolution. Of the lake-stream pairs examined to date, the Misty Lake inlet stream and lake populations appear to be the most genetically and ecologically differentiated from one another. The Misty Lake outlet stream population is intermediate in morphology between the inlet and lake populations and is considered part of the lake-stream complex.

Distribution

The lake-stream pair of threespine stickleback occurs only in Misty Lake and its inlet and outlet tributary system, on northeastern Vancouver Island, BC.

Habitat

Misty Lake, its outlet and inlet are darkly stained and small in size. Sticklebacks in Misty Lake feed in the limnetic zone and spawn in the littoral zone, while those in the outlet are found in slower, deeper water. The inlet stream form remains in either the inlet swamp or the inlet stream, where it is commonly found in deeper, low water velocity areas such as pools and sloughs. Most breeding activity occurs in the stream, with very little in the swamp. Distribution within the inlet system has not been mapped, but appears to be stable.

The lake is considered a natural ecosystem and appears to be stable. The inlet watershed has been logged, but impacts from forest harvesting activities are minor. Misty Lake and short sections of the lower portion of the inlet and the upper section of the outlet are contained within the Misty Lake Ecological Reserve, a part of the provincial protected areas system. However, the majority of the lake’s watershed lies outside the reserve boundaries.

Biology

Although there is ongoing research into the evolutionary biology of the Misty Lake sticklebacks, no detailed studies have been completed on the specific biology of the these fish. In the absence of specific information, it is assumed that they are similar in many aspects to similar forms of the threespine stickleback.

Both forms begin reproductive activity in April and are finished in July (gravid females are common during May and June). There is some information to indicate that the inlet sticklebacks live shorter lives and produce a higher number of eggs at each spawning than lake or outlet fish. Generally, the male stickleback provides parental care. He protects and fans the nest and continues to care for the young fish until they are capable of moving into cover to feed. Eggs take about 7 – 10 days to hatch, depending on water temperature.

Mouth and gillraker morphology suggest that the lake population feeds on zooplankton in the open water of the lake and the stream populations feed on macroinvertebrates.

Studies have shown that the lake sticklebacks will move only in a downstream direction, while those in the inlet sticklebacks will move either upstream or downstream.

Population sizes and trends

Based on overall habitat stability, population trends are also likely stable, although in dry years decreasing water levels may lead to population declines.

Limiting factors and threats

BC Parks has identified potential threats to the stickleback populations within the Misty Lake Ecological Reserve. These include: hydrocarbon and pesticide contamination from the adjacent highway and rest stop; water quality and hydrological changes from nearby logging; non-native species introductions (fish and plants); and non-conforming recreational uses of the lake (canoeing and illegal fishing). The introduction of non-native species has been detrimental to the stickleback pairs in Enos Lake (also on Vancouver Island) and Hadley Lake (on Lasqueti Island, near Vancouver Island).

Special significance of the species

The parapatric stickleback pair found in the Misty Lake system is one of three well-studied lake-stream pairs that display ecotype differences similar to the level seen in the benthic-limnetic stickleback pairs. These highly divergent parapatric pairs are invaluable to the study of evolutionary processes. Genetic data strongly suggest that each highly divergent lake-stream pair has evolved separately through parallel evolution as neither the Misty inlet stream form nor its lake form showed the same genetic ancestry as the pairs from the Drizzle or Mayer lake systems on Graham Island.

Existing protection

The lake is located within the boundaries of the Misty Lake Ecological Reserve, which was established for the protection of the larger lake stickleback. Most of the habitat for the stream form is located upstream of the reserve; this area and much of the Misty Lake watershed is not included in the reserve, making it difficult to ensure the long-term protection of habitat for the whole lake-stream complex.

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 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.

Definitions

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 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) ^Footnotea

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) ^Footnoteb

A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD) ^Footnotec

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.

Canadian Wildlife Service

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