Connecting people with nature in Ontario's Mississippi Valley

Climate Change, Fish and Fisheries in the Great Lakes Basin

Press Release

Mississippi Valley Field Naturalists

Submitted by Pauline Donaldson, MVFN Public Relations Chair

March 6, 2006

Learn how global weather changes are affecting Ontario fish and fisheries

Extremes in global weather, such as those associated with the Pacific’s El Niño and La Niña, and more gradual change such as global warming, affect fish communities in Ontario. Average water temperatures in local freshwater bodies change and this affects spawning, growth, food resources, predation, and, ultimately, the numbers of fish available for recreational and commercial fisheries. This topic will be discussed Thursday March 16, in a seminar by retired Ontario Ministry of Natural Resources scientist Dr. John Casselman, at the Mississippi Valley Field Naturalists meeting in Almonte. According to Casselman, impacts on fish communities and their habitats depend on whether the fish are a warm-water species such as smallmouth bass, a cool-water species such as Northern pike or walleye, or a cold-water species such as lake trout. He plans to use long-term water temperature data for the Great Lakes Basin and age assessments to explain how populations are impacted by temperature change. For example, some very poor years for smallmouth bass were associated with cold temperatures following the 1991 eruption of Mt. Pinatubo. On the other hand his studies suggest a global warming of only 2°C will increase numbers of these fish six-fold, while greatly decreasing the numbers of cool- and cold-water fish.

Dr. Casselman has decades of research experience throughout Ontario and Canada and is currently Scientist Emeritus at Glenora Fisheries Station, an Adjunct Professor at Queens University, and a lead author for fish and fisheries for a key report on climate change in Canada. Dr. Cassleman is also known internationally for his work on the American eel, whose dramatic decline will also be discussed at Thursdays’ talk. In 2003 he convened a conference which led to a global call for immediate measures to sustain eel stocks, which have been negatively impacted by changes in North Atlantic Ocean currents and the Gulf Stream. Remarkably mysterious, all populations of eels live most of their lives in fresh water but return to the Sargasso Sea to spawn, forming a single genetic population. The larval stage drifts on ocean currents for a year before becoming ‘glass eels’ which move to the coasts where, as adults, they inhabit freshwaters in different parts of the world.

The presentation, “Climate Change, Fish and Fisheries in the Great Lakes Basin”, is 6th in MVFN’s series “Change in our Natural World” and takes place Thursday March 16th at 7:30 pm at the Almonte United Church on Elgin St. Host for the evening will be MVFN member Michel Vermette. All are welcome. A non-member fee of $5 applies or MVFN memberships may be purchased. For further information visit or contact Pauline Donaldson at 256-9399.