Air temperature can be a guide to human behavior. As temperatures fall in autumn and early winter, outdoor activity slows dramatically. If outdoor activity ceased altogether, one might say air temperature was a controlling factor in behavior.

It’s not. It’s simply a guideline that points out how most people respond to conditions. Some, for instance, spend more time outdoors in winter than in summer, highlighting individual differences and preferences.

The same is true with fish. Water temperature is a guide that helps us understand how most fish react most of the time, but it’s not an absolute controlling factor. Take panfish in spring. When the ice breaks up in northern states, the water temperature can be as high as 50°F in shallow, dark-bottomed bays with lots of sun exposure. Many of the panfish in any given body of water will be there, feeding—but not all of them. Some stay deeper longer in spring. Those fish tend to spawn later on main-lake spots.

Using temperature as a guide is wise, but thinking of it as a determining factor in fish behavior can be misleading, even when it always seems to work. Fish may move out of so-called comfort zones and stay out. One bluegill may react differently than another to the same temperatures. But we can predict what most panfish do most of the time by using temperature as a guide. So consider the following as general guidelines, not a list of edicts.

Differences North & South

Temperature profile is one of the main differences between northern and southern panfish location in spring. In Minnesota, a shallow bay with good sun exposure generally freezes in November and won’t reach 50°F again until late April or early May. In Florida, a shallow bay on a good panfish lake might never get cooler than 50°F all winter. In Minnesota, when the water hits 50°F in spring, the panfish throw a big party and eat themselves sick. When the temperature drops to 50°F on a Florida lake, the panfish might shut their mouths and refuse to eat again for days.

That’s a drastic contrast, but consider this: Traveling 50 miles north or south usually crosses a substantial climate line anywhere between Canada and Alabama. The panfish in lakes just north of you might shut down during a cold front that hardly affects the lakes near you. The fish of every lake carry with them the genetic reactions to the weather of their own micro environments over tens of thousands of years. That lake 50 miles north? The panfish in it might look the same as those outside your door, but they might react differently to similar conditions. A lake is like a library, each with its own unique genetic lineage.

Micro climates exist that consistently make certain areas on a lake colder than other areas of the same lake—springs, shade, depth, current, and water clarity. Panfish living in an area that’s colder don’t necessarily leave to find warmer water. Forage can become an overriding factor. The fish that do leave deep water to find warmer, shallower water probably aren’t triggered by temperature at all. Panfish sometimes move from water that has been a consistent 39°F for months. The trigger could be length of daylight. Increased sunlight penetration through the degrading ice? Ennui? We don’t always know precisely what triggers panfish to move from winter to spring habitats.