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Invasive Species In Yellowstone Lake Impacted Bald Eagles And Other Creatures In The Region

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Non-native lake trout in Yellowstone National Park are disturbing the existing wildlife populations at the park, new research reveals.

The findings illustrate the potential of a single invasive species to upset entire ecosystems with its presence.

In a new study published in the journal Science Advances, researchers found that the population, diet, and behavior of wildlife in the park have been affected by the presence of the lake trout. Among the species that have been affected are zooplankton, river otters, osprey, bald eagles, bears, elk, and the cutthroat trout.

By examining data from 1972 to 2017, the researchers determined that the impact of lake trout on Yellowstone Lake has spread all across the lake and the surrounding ecosystem, an official report from the University of Wyoming says.

Lake Trout's Invasion Of Yellowstone

According to Todd Koel, lead author and scientist with the National Park Service (NPS), lake trout were first introduced to Lewis Lake in Yellowstone National Park in 1890.

Researchers are still unsure how the predatory fish ended up in Yellowstone Lake, although there are accounts saying the fish were illegally transported there in the 1980s and 90s, according to Newsweek.

Koel says that while there have been accounts of the lake trout affecting the native cutthroat trout, there were less information on the impact of the predatory fish on the greater wildlife population in Yellowstone.

"Effects of introduced predators such as the lake trout were thought to weaken across ecosystem boundaries," Koel explains to Newsweek. "Instead, we witnessed strong effects across the aquatic-terrestrial boundary as native cutthroat trout consumers including bald eagles, ospreys, grizzly bears, black bears, and river otters were lost, displaced, and/or forced to switch prey in the absence of cutthroat trout."

Native Trout, Other Animals Affected By Invasive Trout

The most affected of all the animals is the native cutthroat trout, a species found in the depths of Yellowstone Lake. Numbers of the native fish dropped dramatically after lake trout began preying on them at the lake.

With the decline in cutthroat trout numbers, the presence of zooplankton increased, making the lake water clearer and its temperature warmer.

Fewer cutthroat trout in the water also mean that less nutrients are transported through the tributary streams.

Lake trout live in depths inaccessible to other animals. Since they're eating a good chunk of the cutthroat trout population, many of the predators are finding themselves with less food to eat.

The population of ospreys and bald eagles have decreased, while otters shifted their diet to longnose suckers and amphibians. Even black bears and grizzly bears needed to find alternative food sources due to the decline of cutthroat trout.

For bears, their alternative food likely consists of elk, particularly elk that migrate to Yellowstone National Park during spring.

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