Turning over Lake Turnover
By Alex RobinsonIf you're the type of fisherman who is comfortable spending Saturday mornings indoors watching fishing shows during April and May while waiting for the summer weather to really kick in, then this article is not for you. But if you've already been to the sporting goods store six times this week, your hooks have been sharpened to the point of obsessive compulsion and your boat is tuned up just waiting for ice out, then read on.
It's a giant understatement to say that spring weather in this part of the country is unpredictable; it could be 65 degrees and sunny one day and then snow the next. As anglers we luckily don't have to predict the weather, but by understanding the effects of weather on lake turnover it is possible to at least predict fish behavior.
Crappies are one of the most popular springtime game fish, and their behavior is directly linked to water temperature and lake turnover. To understand what crappies do during this transitional period, we have to first understand what lake turnover really is.
No matter what old Earl tells you down at the corner bait shop, lake turnover does not mean that the lake literally flips over and all the water that was once on the bottom of the lake is now at the surface. More accurately, the lake mixes, and where we are up north this takes place in spring, fall and possibly even several times over the summer.
Generally speaking, cold water is more dense than warm water, meaning that cold water will sink to the bottom and warm water will rise to the surface of a lake. But during the winter months when a lake is frozen, the coldest water is found at the top of the lake. This is because water is most dense at 39.2 degrees and as it gets colder it becomes less dense. This is why ice floats and why water cooler than 39 degrees rises to the surface.
After the ice melts in the spring, most lakes turn over. This means that they become the same temperature from top to bottom, no matter the depth. A lake will stay in this mixed state until its surface warms enough causing it to stratify which Ð depending on different variables like the weather and the size of the lake Ð usually happens by mid-April. By June, lakes in the Midwest are fully stratified.
So what does this mini-limnology lecture mean for crappie fishing? According to Minnesota Department of Natural Resources fisheries biologist Mike McInerny, if you can find the warm water, you can find the crappies.
“Crappies are warm water fish, and in spring they'll seek the warmest water in the lake,” McInerny said. “They're most comfortable in water that is from 58 degrees to 86 degrees Fahrenheit.”
And McInerny claims the old cliche that you can find the bigger fish in deeper water doesn't hold true for springtime crappies.
“The bigger fish actually move into the shallows first,” he said.
It's easier to locate and catch fish early in the season in lakes that start to warm up and stratify the soonest, but McInerny has found one exception. Really shallow lakes that don't have many deep holes often warm up the fastest, but they are usually the same temperature throughout, making it almost impossible to locate fish based on water temperature. Because of this, McInerny likes lakes that warm up quickly but have a variety of depths and water temperatures. If you can find shallow, warm bays in a lake like this you are bound to find crappies
There are several different factors that contribute to a lake warming. Obviously water that gets a lot of direct sunlight will warm up faster than sheltered water. But, another weather factor that is as almost as important as sunlight is wind. As counterintuitive as it may seem, McInerny pointed out that a windy spring day will actually help a lake warm up faster. The wind blows the warm surface water across the lake mixing it up and eventually increasing the lake's overall temperature, McInerny noted.
Another thing to consider is the amount of vegetation and sediment in a lake. According to McInerny, vegetation and sediment help warm water because they retain heat. In addition, shorelines with gradual sloping bottoms will warm faster than shorelines with steep sloping bottoms because gradual sloping bottoms provide more surface area to absorb the sun's rays.
If you can locate areas of a lake offering these features you can bet there will be warmer water there. But unfortunately, during April you can lead a fisherman to warm water, but you can't always make him catch. McInerny was quick to point out that while the fish seek shallower, warmer water in April, it doesn't necessarily mean that they'll be heavily feeding like they do in May before the spawn.
“A lot of times they're just hanging out in there because the water is warmer,” McInerny said.
But after all, that's why they call it fishing and not catching, and, if given the choice between being out fishing or watching someone else do it on television, it's an easy call for me. I'll see you out on the water.
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