Twin Lakes' salinity on the rise to combat plant overgrowth

The Alaska Department of Fish and Game, in cooperation with the City and Borough of Juneau and the Alaska Department of Transportation & Public Facilities, is planning to introduce seawater into Twin Lakes as a means of inhibiting the overgrowth of aquatic plants.


A release states one of the primary purposes of the project is to restore fishing opportunity along the lake shoreline. Reducing the overgrowth of aquatic plants in the lake will also improve opportunity for boating and make the lake safer for swimming.

ADF&G states there was a significant reduction of aquatic plants in Twin Lakes for several years after 2000 when the lake was drained for maintenance purposes and that, while exposure to air and freezing temperatures were partially responsible for reducing plant growth at that time, the higher salinity produced in the lake was also likely a factor.

In the spring of 2010 the salinity in Twin Lakes was raised to levels known to inhibit growth of the plants present in the lake. Raising the salinity of the lake was accomplished through tidal exchanges that repeatedly drained and refilled the lake with seawater. The normal lake level was restored by closing the gate valves after a series of high tides that occurred near the end of March. This project was successful at inhibiting and delaying the growth of aquatic plants for most of the summer months, and therefore additional treatment with salt water is planned for this spring from mid-April to mid-May.

Efforts will be made to prevent stocked fish in the lake from migrating to the ocean during this salt water treatment. Stocking of additional hatchery raised king salmon will occur as usual in early June just prior to the ADF&G Family Fishing Day event.

Questions about this project can be directed to the Douglas office at 465-4270.


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