A gentleman who lives along the Rock River in Byron called me yesterday and wanted to know why I haven’t been talking about the rivers and lakes “turning over.” I told him there probably aren’t too many people who are interested in that. Then last night I opened a few articles on the fall “turnover” and was intrigued!
Here’s what I’ve learned: During the spring and summer months, rivers (and especially lakes) heat from the top-down, thanks to warm wind and sunshine above the surface. This creates a thermocline (or area between warm water above and cool, less oxygenated water below). This is the “happy zone” for most fish species as they are able to gobble up plenty of food, while staying in higher oxygenated water. But when the top layer of water begins to cool, the temperature of the water becomes quite uniform. The uniform temperature means the density of the water is the same…and the water mixes out.
However, this mixing doesn’t occur on every body of water. According to fishingreports.com, windy lakes, lakes with current, or shallow lakes usually don’t even turn over.
When the turnover occurs in the fall, the top (warm) layer mixes with the lower layer, breaking the thermocline. Some signs of a turnover include murky water and sometimes a bad smell. This is due to the dead organisms that fall and decompose at the bottom. For at least a few days after this occurs, the fish won’t feed much, and they’ll scatter to other depths and locations. A friend of mine who fishes regularly says you’re better off to move around during and after the turnover. As things settle down, the fish will come back to their “happy place.” You’ll just have to find where that is and throw your line in there.
My grandpa always said the best fishing happens on cloudy, calm days. And I vaguely remember him talking about the turnover when I was a kid. I’m more of a “baiting the hook for my nieces kind of guy.” What are your experiences out there? Fish stories are welcome here. Just post a comment here, on Facebook, or on Twitter. -Eric
Posted under cold blast, news, science, statistics, sunlight, weather geek, wildlife