Aggressive Suppression of Lake Trout to Restore the Yellowstone Lake Ecosystem

In 1889 lake trout from Lake Michigan were introduced to naturally fishless Lewis Lake within Yellowstone National Park by the US Fish Commission. Upon their discovery in Yellowstone Lake in 1994 the NPS immediately sought expert guidance to mitigate their impact on Yellowstone cutthroat trout, a keystone species in the ecosystem. Since then suppression efforts via gillnetting have progressively increased as the lake trout population has grown and expanded. To date, 830,500 lake trout have been removed. Biomass removed annually has increased exponentially and was 3.2 kg/ha in 2011. Cutthroat trout have drastically declined and several important consumers including grizzly bears, river otters, bald eagles, and ospreys have been impacted as a result. NPS completed NEPA compliance in 2011 to support an aggressive surge in suppression that includes the incorporation of Lake Michigan (contracted commercial) fisherman using gillnets and large live entrapment nets. Modeling suggests that population growth will now be curtailed. However, once lake trout have been suppressed, it remains unclear what efforts will be required to maintain them at low levels. Technologies to improve suppression efficiency must be developed if we intend to recover cutthroat trout and restore the integrity of the ecosystem into perpetuity.