Invasive species cause biodiversity loss and about $120 billion in annual damages in the U.S. alone. Despite plentiful evidence that invasive species can change food webs, how invaders disrupt food webs and native species over time has remained unclear.
Now, thanks to a new collaborative study, there is greater insight into how invasive species progressively affect native food webs. The research was conducted by the University of Montana’s Flathead Lake Biological Station, the U.S. Geological Survey and Montana Fish, Wildlife & Parks.
“This study provides new details about how invasive lake trout affect entire lake food webs,” said U.S. Fish and Wildlife fish biologist Charles Wainright, who recently completed his graduate student work at UM’s biological station. “The findings will be important for conserving native species and ecosystems in Montana and elsewhere.”
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 nonnative fish predator, lake trout, in 10 northwestern Montana lakes. It also analyzed food webs from those lakes to determine how they changed and impacted native communities as the invasions progressed.
The research team showed that lake trout disrupted food webs by forcing native fishes to feed on suboptimal food sources in different habitats, eventually causing the loss of the native predator, bull trout, a threatened species protected under the U.S. Endangered Species Act.
“Native bull trout populations have drastically declined in many lakes across western Montana due to competitive interactions with invasive lake trout,” said Clint Muhlfeld, a USGS aquatic ecologist and FLBS associate research professor. “For the first time, we show what happens not only to bull trout but entire food webs supporting them as lake trout invade and upset lake ecosystems over time.”