Research Document - 2009/100

Information used in the Recovery Potential Assessment for the misty lake stickleback pair

By B. Harvey

Abstract

Misty Lake drains into the Keogh River on northern Vancouver Island. The lake supports two forms of stickleback, a small coastal fish found in both fresh and salt waters: one form lives in the lake, the other in the inlet and outlet streams. It is one of only three clearly defined lake-stream pairs in Canada and has been studied for decades as a model for understanding the evolutionary process. The Misty Lake stickleback pair was designated Endangered by COSEWIC in 2006 because it is an endemic, highly divergent species pair restricted to a single lake-stream complex. It is presently being considered for listing under the Species At Risk Act (SARA). The B.C. Conservation Data Centre designates the species “S1” (Critically Imperiled and Red-listed). It was afforded some protection from creation of the Misty Lake Ecological Reserve in 1996.

There are insufficient data to describe the species’ critical habitat other than as “synonymous with its known distribution”, with the understanding that its penetration into inlet and outlet streams requires further study. Given the lack of knowledge of abundance or trends, it is not presently possible to establish population or distribution targets.

The main human-caused threats to the Misty Lake stickleback are introduction of alien species, runoff from the Highway 19 rest stop, and changes in water quality that affect light transmission, dissolved oxygen and productivity. All must be viewed not only in terms of their effect on population numbers, but also for their likelihood of causing hybridization between the lake and stream forms. Hybridization is the reason for the collapse of the Enos Lake stickleback pair on southern Vancouver Island. Because the main importance of the Misty Lake stickleback pair is its existence as a pair, the risk of their becoming a genetically homogeneous single population is as important as the risk of simply losing individuals. Critical habitat thus becomes not only that which is needed to maintain abundance of the two forms, but also that which is needed to keep them from interbreeding.

Options for minimizing human activities and threats to habitat include expanding the ecological reserve to include the full length of the inlet streams; moving the rest stop to another stretch of Highway 19; aggressive signage and other means of raising public awareness concerning invasive species; ensuring that timber harvesting does not alter dissolved organic carbon in the wetland where the inlet enters the lake; instituting a precautionary captive breeding program to preserve the gene pool; and sharing information and research.

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