Fish behavior and activity is related greatly to water temperature. In general, fish are less active in cold water. As the temperature increases through the day or season, fish spend more time actively feeding. For example, largemouth bass may be inactive on cool mornings but more energetic in areas when the sun begins warming dark rocks or submerged logs. There is a limit, though. Too hot can lead to conditions with less oxygen and can turn off a bite or send fish to deeper, cooler water.
Some fish like spotted gar and channel catfish not only tolerate but thrive in warm water, above 80 degrees. Trout and salmon prefer much cooler temperatures. Writer Tom Keer shared an interesting fact that trout will “process a stomach of food every four days.” If the water temperature is above or below 55-65 degrees, the stomach is efficiently digested daily. Some species just won’t tolerate cold temperatures at all. Tilapia and threadfin shad start dying if the water drops below 45 degrees.
This handy chart has optimum temperatures for other species, as well as upper and lower “avoidance” temperatures.
Although tied to other factors such as tides and day length, temperature influences fish behavior such as migrating or spawning. For example, pelagic species such as tarpon will move to remain in water temperatures of 72 to 82°F. Pro bass fishing angler Kevin VanDam starts to look for largemouth bass in prespawning staging areas when the water hits 50 degrees and adjusts his methods accordingly.
While trying to figure out this whole “fishing thing,” I’ve started to bring a floating pool thermometer, recording this data in my handy Fishing Journal. Simply dangling fingers in the water to judge if the water is “too hot,” “too cold,” or “just right,” may not be enough. Knowing how temperature affects fish behavior can help with lure selection, how to work it, and thus, catching more fish.