Lake trout were introduced into Yellowstone Lake during the 1980’s and have dismantled Yellowstone’s natural ecosystem ever since. Yellowstone cutthroat trout have declined by upwards of 90 percent, according to National Geographic. The non-native lake trout are terrorizing cutthroat trout populations, mostly by physically eating their native cousins.
A 1998 National Park Service scientific report estimated that in that year, 125,000 lake trout consumed 3-4 million cutthroat trout. Consequently, this decline of cutthroat trout and emergence of lake trout had resounding effects throughout Yellowstone’s ecosystem with strong effects felt by just about every level of the food chain. Bird populations and even bears have been negatively affected, as there once-primary food source is historically scarce.
Photo courtesy of Pat Clayton @Fisheyeguyphotography
Thankfully, scientists have known the problem and are actively working to restore Yellowstone cutthroat trout populations. The goal is to remove as many lake trout as possible, mainly through gill nets and encouraging anglers to remove any non-native species they catch. Hopefully, these efforts among others will allow cutthroat trout to return to their historic levels.
Check out this article by National Geographic that describes the issue in more detail!
Trout Unlimited has also published a more recent article on the matter, that is worth checking out! https://www.tu.org/blog-posts/return-of-the-yellowstone-cutthroat
Also, take a look at these Flylords’ articles involving cutthroat trout: The Difference Between Rainbow and Cutthroat Trout and High Country Haven.