Seattle Press on Line - It's a Jungle Out There: Carp and Muskies Attack Green Lake's Ills

It's a Jungle Out There: Carp and Muskies Attack Green Lake's Ills

Jan 11, 2001 -- The Seattle Parks Department is looking at a plan to introduce 1,000 Asian grass carp into Green Lake, which is choking on an abundant growth of algae, milfoil, and other aquatic plants.

Milfoil is a freshwater weed that grows into thick mats and can prevent sunlight from getting below the lake's surface, which contributes to algae growth and eutrofication (oxygen depletion). The milfoil is thriving, in large part, because of fertilizer runoff from lawns in the surrounding neighborhoods that drain into the lake.

Eutrofication is the process by which algae and weed growth consume the oxygen in the water, gradually destroying fish and amphibian habitat and turning the lake into a weed-choked swamp.

The carp being considered for aquatic lawn duties are sterile, and are notorious grazing vegetarians. Thus they won't reproduce, and they won't eat other creatures in the lake. The carp, which can reach 60 pounds in size, are often classified as a game fish, and are considered to be the best eating of any of the carp species. In fact, the Arkansas Game and Fish Commission installs them in Arkansas waters to be caught and eaten.

Chemical and mechanical means have failed to control milfoil and algae, according to Christopher Williams of the Parks Department. Alum was added to the lake water a few years ago to control algae, unsuccessfully, and a huge underwater lawnmower that used to chug around mowing the milfoil six feet under water now sits forlornly in the middle of the lake. It is hoped that the carp will be the key to a healthy Green Lake.

Several hundred tiger muskies were installed in the lake in November by the Washington Department of Fish and Wildlife. The sharp-toothed, sweet-fleshed fighting fish are intended to eat the pesky little bluegills and sunfish that poke around in the lake bottom, stirring up the sediments and releasing nutrients that support algae blooms. The muskies, which can get as big as 25 pounds, could provide some real thrills for Green Lake anglers.