08/09/2012 05:27 EDT | Updated 10/09/2012 05:12 EDT

The Great Lakes (and the Fish in Them) Are Overheated


Ontario's coldwater fish aren't singing along to Hot Fun in the Summertime these days. That's because as water temperatures increase due to global warming, the mix of fish species is changing. Warm water fish, like small mouth bass, are doing better. Coldwater fish, like pike and lake trout, not so much.

The U.S. drought is killing fish in higher numbers than usual. There have been more than 70 widespread fish kills in July in the U.S., in Michigan, Minnesota, Wisconsin, Indiana and Illinois. One kill alone felled about 350 northern pikes. They are attributing these kills to high water temperatures, which lead to algae blooms, which in turn strip oxygen from the water. Higher temperatures can also trigger fatal virus outbreaks.

In Ontario, I learned, we are not experiencing unusually high fish die offs this year. The authorities also haven't declared a drought. But global warming is affecting Great Lakes water temperatures, which does have serious implications for our fish.

Scientists are a careful bunch, so when a scientific paper says, "global warming will significantly affect" fish in the Great Lakes Basin, it's time to perk up.

John Cassleman, a former Ministry of Natural Resources scientist, now an adjunct professor in Biology at Queen's University, researched the impacts of water temperatures in eastern Lake Ontario on fish survival and abundance over three decades. He found that summer and early winter inshore water temperatures have increased in parallel with temperature increases. Since higher water temperatures favour warm water fish, more warm water fish, and their eggs survive -- while fewer cool and coldwater fish survive.

Water temperatures are increasing in the winter as well as the summer. When we have a warm winter, less ice forms, and because there's less white ice and snow to reflect the sun's rays, more heat is absorbed by open water. Great Lakes ice coverage has declined an average of 71 per cent over the past 40 years. It's down by a whopping 88 per cent in Lake Ontario.

These changes are serious. The Great Lakes' problems are complex, due to the impacts of pollution, resource and land uses, and invasive species. And the extreme weather we are experiencing increasingly as a result of global warming makes these complex problems even more difficult to manage.

To adapt to climate change, we need to keep streams and shorelines well shaded with natural greenery and let streams flow naturally rather than allowing water to warm up in reservoirs and pools. But what we really must also do is mitigate global warming by reducing our greenhouse gas emissions -- by embracing energy efficiency, renewable energy and building better public transit.

If you like to fish, do it late at night or early in the morning when it's coolest and less stressful for the fish. If you're uncomfortable, the fish are probably too! And if you're lucky enough to get something on your line, handle the fish as little as possible.

To have a future full of fun fish frys, we all need to help this planet cool down.