The Cosby method


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Montana State University ecologist Al Zale recently offered up a few ideas for dealing with an infestation of invasive lake trout in Yellowstone Lake, but one seems to be bogarting all the attention. Zale suggests going out during the fall and smothering the trout eggs with Jell-O.

“Unflavored gelatin might be a better way to put it,” Zale clarifies.  “The lake trout spawn on rocky reefs in lakes and tend to congregate in certain areas. The thought is, because they spawn over a relatively small area, that it might be possible to go in and kill them in one way or another.”

Gelatin—the processed collagen from animal bones—would essentially deprive the lake trout eggs of the oxygen they draw out of the water. It’s a natural, biodegradable solution, and a relatively cheap one to supplement gill net harvesting as a tactic for purging Yellowstone Lake of the nuisance fish. The other available options include ultrasound, microwave radiation and electro shocking.

Native to the Great Lakes, lake trout pray upon indigenous Yellowstone cutthroat, which, though not as threatened as their westslope cousins, face similarly dwindling numbers due to nonnative competition and outbreaks of whirling disease. Yellowstone Lake constitutes the largest reserve of Yellowstone cutties in North America—a population threatened since rangers first discovered lake trout in 1994.

“Lake trout are voracious predators. They get big and eat a lot,” Zale explains. “The lake trout’s primary source of food in Yellowstone Lake is the Yellowstone cutthroat.”

The researcher’s work is financed by a National Park Service grant—perhaps the first in a series—seeking to eliminate the lake trout pest permanently. Despite
harvesting upward of 18,000 trout from Yellowstone Lake every year, park rangers can’t knock out the invasive species because the adolescent trout stay
deeper under the surface than gill nets can reach.



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