The Fish That Destroyed the Yellowstone Ecosystem

National Geographic has a troubling article on how one fish has, and is, changing the ecology of Yellowstone National Park (YNP).

The introduction of lake trout into Yellowstone Lake has led to the demise of the native cutthroat trout (see photo above). That in turn has led to a cascading effect in various food chains.

The absence of cutthroat that no longer swim up creeks to spawn means grizzly bears, that used to feed on them, are now killing more elk calf – more than are taken by wolves. Also impacted are river otters, as well as bald eagles and other fish-eating birds.

The presence of osprey has decreased dramatically. In the early 1990’s there were 62 osprey nests documented around Yellowstone Lake; last year (2017) there were three. Scientists believe the osprey, being fish eaters, left the area and have gone elsewhere.

But it is the bald eagle that has had the devastating impacts on YNP’s birds. As opportunistic feeders, they have turned to eating various species of native birds such as cormorants, loons, pelicans, swans, and terns. And the local extinction of some of their prey species appears to be near.

The number of loons has declined by 50 percent since 1990. Just 18 breeding pairs remain in Wyoming, with 70 percent of those in YNP.

Efforts have been underway to reduce the numbers of lake trout; elimination appears to be impossible. The result has been to somewhat stabilize the cutthroat populations. However, it could take decades – if even then – to increase cutthroat population to the point they can again be a food source for bears, eagles, and other animals.

Combine that with the increasingly obvious impacts of climate change and the future does not look bright. And this is Yellowstone National Park, where efforts have always been about preserving a complete ecosystem.

A question might be how did the non-native lake trout get into Yellowstone Lake? Evidence suggests they were illegally introduced sometime in the 1980s. No one knows who or why. But the suspicion is that someone decided they wanted to increase the numbers of fish for fishing.

Perhaps it was only one bucket of lake trout fry; maybe more. But in any case, that single act has led to a cascade of effects that may forever have changed a major ecosystem.

Our individual actions do have consequences.

You can read the article here.

Author: Tom

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