Researchers Find Evolutionary Adaption in Trout of Wyoming's Wind River Mountains
Published:23 Aug.2023 Source:University of Wyoming
The lakes in Wyoming's Wind River Mountains historically didn't contain fish, but stocking of trout that began in the early 1900s has created an environment in which hundreds of those lakes now have strong fish populations -- some carried on by natural reproduction for decades. This environment also has provided a laboratory for researchers to study the ecosystem changes in the once-fishless alpine lakes, to which anglers today make long hikes to pursue cutthroat trout and relatively rare golden trout. Previous research found that the introduction of fish in the lakes of the Wind Rivers has driven a decrease in the size of zooplankton, the small aquatic organisms on which the trout feed. Now, University of Wyoming researchers have found that the fish themselves have adapted to their environment -- "rapid evolution" that sheds further light on the introduction of invasive species.
During the summers of 2018-2021, the researchers collected fish from 18 lakes in the Wind Rivers previously stocked with Yellowstone cutthroat trout, which come from northwest Wyoming, and golden trout, which come originally from the Kern River drainage in California but were first stocked in the Wind Rivers in the early 1900s. The lakes included fish populations that were started decades ago as well as more recently stocked populations. The researchers then compared the fish of the Wind Rivers with golden and cutthroat trout produced in Wyoming Game and Fish Department hatcheries.
The researchers found that the trout from lakes stocked decades ago in the Wind Rivers have higher numbers of gill rakers, which are bony or cartilage structures in the gullets of fish that act as sieves to retain zooplankton and nourish the trout. The scientists say the difference is likely a result of the trout adapting to the food sources of the high-mountain lakes -- a change that has taken place in a relatively short period of time and at a rate that is generally consistent with the historic timing of stocking for each of the lakes. The findings are evidence that eco-evolutionary interactions play a critical role in ecosystem ecology.