As Midwestern Lakes Warm, Fish Face Asymmetrical Impacts
Midwest CASC-supported research shows that cooler-water fish are losing habitat faster than warmer-water species are gaining habitat, indicating that managers can expect more fish species “losers” than “winners” in midwestern lakes.
Freshwater fish rely on the environment to regulate their body temperature and often need specific thermal conditions to survive. This can be challenging for fish in lakes who have limited abilities to move out of their lake habitat as the conditions around them change. As climate change raises water temperatures, the thermal habitats within lakes are shifting, depending on several factors like lake depth, morphology, and water clarity.
In a new study, researchers supported by multiple Midwest CASC projects analyzed changes in thermal habitat for 60 freshwater fish species, considering the geographic range of the species, lake temperature cycles, weather, and lake features (like depth and clarity). Researchers examined daily temperature profiles from over 12,000 lakes in the midwestern U.S. to track how many days each year the lake provided “preferred” temperature ranges for these species. Then, by comparing data from 1980-2000 to data from 2001-2021, they assessed how thermal habitats have shifted over time. The findings showed that cooler-water fish (those preferring temperatures below 20.5 °C) are losing days of ideal temperature habitat much faster than warmer-water fish (those preferring temperatures above 20.5 °C) are gaining them. The imbalance is caused by seasonal lake temperature patterns and increasing temperature uniformity in the water column, rather than the spatial distribution of fish species across different sets of lakes where they are found.
Findings from this study suggest that warming could cause large habitat losses for cooler-water species, with habitat gains for warmer-water species unlikely to offset these losses. These insights about how climate change will affect inland fish communities provide important considerations for lake and freshwater fisheries management in the region.
This research was supported by the following Midwest CASC Projects:
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