By Montana Grant

Posted: April 27, 2019

Yellowstone Lakes wonderful Cutthroat trout fishery is in rough shape. There are many reasons for this major population decline. The entire ecosystem needs to be examined and addressed if there is any hope for Cutthroat trout recovery and ecosystem repair.

Recent studies completed by the University of Wyoming and fishery agencies are trying to repair the damages. The introduction of the non-native lake trout has altered more than the Cutthroat population. All creatures from the microscopic plankton to the large animals in the region are affected.

The diets and behaviors of eagles, otters, bears, and all critters have been altered as a result of the invasive lake trout. Researchers examined date from the past 40 years starting in 1972.

Here is what they found.

Zooplankton size in the lake has increased.

               Water clarity has increased

               Lake surface temperatures have increased

Fewer spawning Cuts, in tributaries, reduced the transport of nutrients, such as ammonium, to those streams. Plants and organisms are affected.

The density of ospreys, elk, and other mammals have declined

Bald Eagles have shifted their diet and are less abundant in the region. They now prey on loons, swans, pelicans, and other critters.

Otters are now feeding on amphibians and longnose suckers. They are also declining.

Black and Grizzly Bears have changed feeding habits. Other mammals and food sources, like young elk and buffalo, are being pressured. Most migratory patterns continue to change.

The massive forest fires in 1988 were not responsible for the cutthroat decline. Wolves were reintroduced into Yellowstone Park in 1995 and the discovery of the invasive lakers was the following year. There is no evidence that wolves have impacted the trout.

The extensive current gill netting of lake trout, over the past 24 years, is beginning to work. Cutthroat trout populations are starting to increase, and more spawning is evident. Lake trout reproduction, numbers, and size have declined. Over time, the other critters will also recover. The final outcome of this ecological crisis remains uncertain.

Nature Knows Best!

Montana Grant

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