Lake Montana study reveals how invasive species affect native food webs

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Vin D’Angelo, a USGS fisheries biologist, shows a non-native lake trout that was recently caught in Logging Lake in Glacier National Park. Credit: Joe Giersch, USGS

Invasive species cause biodiversity loss and an estimated $ 120 billion in annual damage in the United States alone. Despite ample evidence that invasive species can alter food webs, how invaders disrupt food webs and native species over time has remained uncertain.

Today, thanks to a new collaborative study, we have a better idea of ​​how invasive species are gradually affecting native food webs. The research was conducted by the University of Montana’s Flathead Lake Biological Station, the US Geological Survey, and Montana Fish, Wildlife & Parks.

“This study provides new details on how the invasive lake trout affects all of the lake’s food webs,” said U.S. fish and wildlife biologist Charles Wainright, who recently completed his graduate student work. at the UM biological station. “The results will be important for the conservation of native species and ecosystems in Montana and beyond.”

The study, recently published in the prestigious journal Proceedings of the National Academy of Sciences, used long-term fisheries monitoring records to determine the timing of invasion by a non-native fish predator, lake trout, in 10 lakes in northwestern Montana. He also analyzed the food webs in these lakes to determine how they changed and impacted Indigenous communities as the invasions progressed.

The research team showed that lake trout disrupted food webs by forcing native fish to feed on suboptimal food sources in different habitats, ultimately causing the loss of the native predator, Bull Trout, a species Threatened protected by the US Endangered Species Act.

“Native bull trout populations have declined dramatically in many lakes in western Montana due to competitive interactions with invasive lake trout,” said Clint Muhlfeld, USGS aquatic ecologist and associate professor of FLBS research. “For the first time, we show what happens not only to Bull Trout, but to entire food webs that support them as lake trout invade and disrupt lake ecosystems over time.”

The study also showed that the effects on the food web of the lake trout invasion were particularly pronounced as lake trout abundance increased rapidly 25 to 50 years after colonization. After 50 years, lake trout were the dominant predator in these food webs. The study shows that with sufficient time, invasive lake trout can disrupt and replace a native fish species, such as bull trout, and create divergent biological communities that are very different from uninvaded ecosystems.

This study adds to a body of evidence showing that invasive species have affected western Montana. For example, until the late 1800s, a dozen native species of fish patrolled the waters of Flathead Lake, including abundant westslope cutthroat trout and bull trout. Beginning in 1905, fishery managers began to introduce non-native species into the food web in order to enhance Flathead Lake tourism and generate more appeal for recreational fishing. Today, there are over 20 species of fish in Flathead Lake, and introduced species such as lake trout, lake whitefish and Mysis shrimp dominate the Flathead Lake food web, so much so that native species, including Bull Trout and Westslope Cutthroat – the state fish – have declined dramatically.

“It has been a real collaborative effort,” said Shawn Devlin, FLBS Lakes Ecologist. “The work draws on the rather dark history of the introduction and invasion of non-native species into the lakes of northwestern Montana in an ecological experiment grounded in the power of long-term data and understanding. more in-depth look at lake ecology. “

The results of the study highlight the importance of protecting entire landscapes from biological invasions. The use of innovative biomonitoring surveillance techniques, such as environmental DNA, is also key to increasing the likelihood of detecting invaders before they become established. For ecosystems that have already been invaded, the results of this study may inform proactive control efforts during the early stages of invasion to avoid disruptions to the food web that can be difficult to reverse.

The study, led by Wainright, was co-authored by Muhlfeld, Devlin, FLBS Director Jim Elser and Samuel Bourret of Montana Fish, Wildlife & Parks.


Genetic mapping strengthens hopes of restoring precious lake trout


More information:
Charles A. Wainright et al, Species invasion progressively disrupts the trophic structure of native food webs, Proceedings of the National Academy of Sciences (2021). DOI: 10.1073 / pnas.2102179118

Provided by the University of Montana

Quote: Lake Montana Study Reveals How Invasive Species Affect Native Food Webs (2021, November 4) Retrieved November 4, 2021 from https://phys.org/news/2021-11-montana-lake-reveals -invasive-species.html

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