Largemouth bass today aged 0 through 11 years are statistically smaller today
Posted: Wed Nov 05, 2025 4:34 am
Fishes, young and old, are shrinking in Michigan's inland lakes
Peer-Reviewed Publication
University of Michigan
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Lake trout museum specimen
image:
Researchers will also include museum samples, like this lake trout, in their future work studying the impacts of climate change on fishes in Michigan's inland lakes. Image credit: Peter Flood
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Credit: Peter Flood
A new study led by the University of Michigan shows that changes in climate are also changing the size of fishes in Michigan's inland lakes. Using data that covered 75 years and nearly 1,500 lakes, researchers have shown that, for several species, old and young fish in 2020 were significantly smaller than their typical size in 1945.
"Climate change is altering the size of different organisms around the world, including fishes in lakes here in Michigan," said Peter Flood, a postdoctoral research fellow at the U-M School for Environment and Sustainability, or SEAS. "And most of those changes we're seeing in Michigan fishes are declines in size through time."
Flood is also the lead author of a new study published in the journal Global Change Biology and was supported by the U.S. National Science Foundation and Michigan Institute for Data and AI in Society, or MIDAS. The report is the latest to make use of data amassed by a community science project that digitized decades worth of observation cards that characterize fishes over time in 1,497 inland lakes in Michigan.
This allowed Flood and his colleagues not only to track the sizes of 13 different species, but also of different age groups within those species. The team found that, out of 125 species-age class combinations, 58 had changed size. Of those 58 that changed, 46 were smaller.
"The largest decreases in length over time were found in the youngest and oldest fishes," Flood said. "Both of those groups have outsized roles in maintaining healthy fish populations and ecosystem functions and services."
The predators of these fishes are largely gape limited, Flood said, which means they can only eat what fits in their mouths. When younger fishes are smaller, then, they're easier prey, which can limit the population of not only the current generation, but future ones as well. And while older fishes don't have the same impact on population dynamics, they still have important roles in their communities, he said.
Read it all: https://www.eurekalert.org/news-releases/1104614