Trout adaptations reveal rapid evolution in Wyoming’s restocked alpine lakes

Wind River Mountain range, Wyoming
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August 3, 2023 — Science DailyOpens in a new tab. reports that the Wind River Mountains in Wyoming didn’t have any fish in their lakes. That changed in the early 1900s when trout were stocked, transforming the alpine lakes in the region and creating  “natural research labs.” Today, these lakes boast thriving fish populations, which have been maintained naturally for many years.

A Natural Lab for Researchers, Insight on Evolution of Invasive Species.

This transformation has not just benefited anglers who enjoy long hikes to fish for cutthroat trout and the relatively scarce golden trout. It has also served as a research ground for scientists to investigate the ecosystem changes in these previously fishless alpine lakes.

Prior studies noted that the addition of fish to the Wind River lakes led to a decrease in the size of zooplankton, the tiny aquatic creatures that trout eat. Recently, researchers from the University of Wyoming discovered that the fish themselves have undergone rapid adaptation to their new environment. This discovery provides more insights into how invasive species evolve.

Fast-Paced Evolution in Small Populations.

According to the scientists’ findings published in the journal EvolutionOpens in a new tab., even small initial populations can adapt swiftly to new environmental and evolutionary pressures, especially during rapid environmental changes.

Over the summers from 2018 to 2021, the research team gathered fish from 18 lakes in the Wind Rivers. These lakes had been previously stocked with Yellowstone cutthroat trout, native to northwest Wyoming, and golden trout, initially from California’s Kern River drainage. Both species were introduced into the Wind Rivers in the early 1900s. The lakes hosted fish populations that had been established for several decades as well as more recent additions.

The researchers compared the Wind Rivers’ trout with the golden and cutthroat trout bred in Wyoming Game and Fish Department hatcheries and discovered that trout from lakes in the Wind Rivers, stocked decades ago, developed a higher count of gill rakers. Gill rakers are bony or cartilage structures located in a fish’s throat that work like sieves to catch and retain zooplankton, providing essential nutrition for the trout. This development suggests that the trout have adapted to the high-mountain lakes’ food sources.

This adjustment, according to the researchers, has happened over a relatively short time frame. The speed of adaptation correlates closely with the historical stocking timeline for each lake.

The Role of Evolution in Ecosystems.

The study’s results emphasize the crucial role that evolution and adaptation play in shaping an ecosystem. These observations give us a clearer understanding of the patterns and timing of adaptive change that results from human intervention. Moreover, they offer insights into how evolution can assist species in adapting to resource-limited, rapidly changing environments.


South end of the west aspect of Haystack Mountain (left), Steeple Peak, and East Temple Peak (right) seen at sunset from Deep Lake. Wind River Range, Wyoming, Intermountain Forest Service, USDA Region 4 Photography, via Wikimedia CommonsOpens in a new tab..


Since 1995, Deborah has owned and operated LegalTech LLC with a focus on water rights. Before moving to Arizona in 1986, she worked as a quality control analyst for Honeywell and in commercial real estate, both in Texas. She learned about Arizona's water rights from the late and great attorney Michael Brophy of Ryley, Carlock & Applewhite. Her side interests are writing (and reading), Wordpress programming and much more.

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