by Donna Gleisner and Bruce Crawford
Reprinted from Washington Wildlife, Fall 1980.
No one suspected that Mount St. Helens would utterly devastate 100,000 acres of the Cascade Mountains on that calm Sunday morning, or that it would happen with such force in just a matter of minutes. A 100-400 mile per hour lateral blast from the north face seared the surrounding countryside and alpine lakes with temperatures of up to 500 degrees F and engulfed all life in a deadly blanket of fallout.
All 37 lakes within the Mount St. Helens National Volcanic Monument received the full brunt of that natural, yet terrifying, phenomenon. The blast's destructive forces denuded most shorelines of anything green and growing. In their place settled a layer of hot, gray ash that choked off light and life and superheated the waters.
At that time the lakes, all managed by the Washington Department of Game for trout fishing, contained a mixture of eastern brook and cutthroat trout. Most lakes were planted by helicopter or plane on a three-year rotation basis. Fifty to 100 fish per acre was the norm, meaning that as many as 150,000 fish could have been in the lakes at eruption time.
Conditions looked extremely dismal immediately after the blast. The suspension of ash in the lakes along with super hot temperatures severely reduced the aquatic plants and animals abilities to survive. But to find out exactly what the conditions were in the blast zone, biologists from state and federal agencies decided to helicopter in as close as they dared, starting in July. This was the beginning of four years of research.
From July 1980 through August 1984, 21 lakes were surveyed by the Washington Department of Game. Surprisingly enough, live populations of trout were found in two-thirds of them: Elk, Fawn Hanaford, Island, Little Venus, Merrill, Meta, Obscurity, O'Connor, Panhandle, Shovel, Strawberry, Tradedollar and Venus. Of the seven remaining lakes where gill net surveys failed to produce fish, only three lakes -- Boot, Ryan and Spirit -- appear to have lost their populations due to the eruption of Mount St. Helens. Two of the seven barren lakes sampled probably didn't contain any fish prior to the eruption because they were too shallow.
Of those waters with surviving populations, eastern brook trout were either the dominant or the only fish species found in most. Cutthroat were found in only four lakes and lake trout in one. it seems that in the lakes where cutthroat were stocked on top of self-sustaining brook trout populations, only brooks survived the stress and competition imposed by the blast.
The good news is that many lakes still retain the habitat needed for natural spawning to take place in inlet or outlet streams. And evidence so far indicates that eastern brook trout are again successfully spawning in at least three lakes and cutthroat in one lake. The reason? Aquatic insects somehow managed to survive the blast's effects or quickly repopulated the devastated lakes. Just that little bit of life, plus the self-cleansing action of the water itself, enabled life in those lakes to respond rather quickly -- in one to three years. Now aquatic life, including fish, is rapidly approaching, and in some lakes even exceeding, its preeruption population levels.
Selected lakes outside the Monument, such as Hanaford, were stocked beginning as early as 1982 and receive quite a bit of use. But within the Monument itself, a five-year moratorium on stocking fish is in effect. This allows researchers time to complete their studies before fish are reintroduced on an artificial basis.
Bruce Crawford, regional fish biologist for the Department of Game, believes that all natural lakes, including Spirit lake with its abnormally high nutrient levels, are very capable of sustaining populations of trout. He also thinks the two newly-formed lakes, Castle and Coldwater, are capable of doing the same on an even larger scale.
The future of these alpine lakes and their fish populations depends upon proper management and adequate public access -- something that the Washington Department of Game and the Gifford Pinchot National Forest are working closely together on. We want to not only meet the recreational needs of our sport fishing public, but to also remain aware of the unique research opportunities and the fragile life within that seeming desert of ash.
Donna Gleisner is a Department of Game Conservation Education Programs Specialist and Bruce Crawford is a Regional fish Biologist, both in Region Five, Vancouver.