New Research Published in the Canadian Journal of Fisheries and Aquatic Sciences

Exciting discoveries emerge out of the University of Guelph from an investigation into the impact of climate change on five key freshwater fish species! A new study published in the Canadian Journal of Fisheries and Aquatic Sciences and carried out with the assistance of the CEM’s Director, Dr. Kevin McCann, looks at how freshwater fish body sizes respond to warming.

Ecologist and co-author Connor Warne.

The study delves into the natural communities of Lake Trout, Lake Whitefish, Walleye, Yellow Perch, and Smallmouth Bass; each vital for culture, commerce, and recreation. Instead of relying on lab experiments, ecologists combed through a massive dataset of over 170,000 records from 600+ lakes across Ontario, Canada.

The findings, powered by advanced spatial analysis techniques like INLA (Integrated Nested Laplace Approximation), unveil a dynamic response to warming lake conditions. As the lakes warmed up, the fish responded in different ways. The Lake Whitefish, a cold-adapted species, got smaller. On the other hand, Walleye and Smallmouth Bass - which are both considered to be cool and warm-adapted species - actually grew in size.

This study echoes the findings of others recently conducted in marine and freshwater systems with respect to the realization that fish body sizes don't follow a simple, one-way trend with warming. Instead, it's a complex dance influenced by the unique habitats and thermal preferences of each species. This adds a fascinating layer to our understanding of how climate change shapes the dimensions of aquatic life.


Connor Warne, Dr. Matthew M Guzzo, Dr. Kevin Cazelles, Dr. Cindy Chu, Dr. Neil Rooney, and Dr. Kevin S. McCann. 2024. Thermal tolerance and habitat preferences mediate how freshwater fish body sizes respond to warming. Canadian Journal of Fisheries and Aquatic Sciences.

Helen Vanos