Until the last couple of years, the decline in the native cutthroat trout of the lake has been dramatic, and possibly catastrophic. The lake trout subsist on a diet almost exclusively of other fish – in this case, cutthroat. Where once literally millions of cutthroat thrived in Yellowstone Lake, and each spring spawned by the tens of thousands in the rivers and streams feeding the lake; today the numbers are in the hundreds.
Since the early 1990’s the Park Service has been fighting the infestation of lake trout. Gill netting has been used for years, and to-date has netted over 270,000 lake trout at a cost of $3,000,000. Despite the effort, the lake trout have prospered and the cutthroat trout have declined to less than 10% of their original population.
The cutthroat trout of Yellowstone Lake are – or were – the largest repository of this native Rocky Mountain fish. Their spring spawning run provided food at a critical time for many other species including grizzly and black bears, otters, pelicans, comorants, ospreys and eagles. The decline in cutthroat population will have a ripple effect in the environment of the park, although studies need to be done to document the changes.