What happens when the trout streams warm?
U.S. Geological Survey scientists have completed one of the first experimental studies to explore links between climate change and invasive species, specifically how brook trout and brown trout interact with rising stream temperatures. They found that non-native browns limit the ability of brook trout to use warmer water temperatures, By contrast, removin of browns brook trouts’ reach into warmer waters.
Brookies are freshwater fish native to eastern North America and threatened by climate change because of their requirement for cold stream temperatures. Brown trout are native to Europe and have been introduced all around North America.
“We know streams are warming due to climate change and non-native species are becoming increasingly abundant in many places,” said Nathaniel Hitt, U. S. Geological Survey research fish biologist. “Our research indicates that reducing Brown Trout numbers can benefit native Brook Trout where the species co-occur,” Hitt said. Brown trout management could help brookies be more resilient to anticipated effects of climate change, he added.
The researchers found that native brook trout are less resilient to climate change compared to the browns because the native fish has less tolerance to higher water temperatures. Since the food sources were located in the warmer waters during the study, brookies ability to feed was reduced when they competed with brown trout.
The study was conducted at the USGS Experimental Stream Laboratory at the Leetown Science Center in Kearneysville, West Virginia, where the scientists control water temperatures in a series of replicated stream channels. Using underwater video sampling, scientists were able to evaluate brook trout responses to water temperature change in the presence and absence of Brown Trout.
“Our study shows that climate change and non-native species should be considered in tandem when evaluating effects on native fish,” Hitt said. “In many cases these changes are happening simultaneously, so we need interdisciplinary research such as this study to anticipate how these changes will interact in the future.”
This study was published in the Canadian Journal of Fisheries and Aquatic Sciences and can be accessed here: http://www.nrcresearchpress.com/doi/abs/10.1139/cjfas-2016-0255.