To me there's nothing like slipping into a comfortable tub of hot water after a hard day's work. Something about those warm waters swirling about, gently tickling my toes, easing my aching muscles, just leaves me with a really special sensation. Bass feel exactly the same.
Bass simply love being warm. Indeed, bass, bluegill and others are some of the most thermophilic freshwater fish around sometimes too much so for their own good.
Like virtually all fish, bass of course are cold-blooded animals, meaning their body temperature is not set to a constant as it is in mammals. Instead, because water sucks out any excess metabolic heat like a sponge, the body temperature of a bass is nearly always virtually identical to that of the surrounding water. It's the water not the bass that sets the bass' body temperature.
Now, you might think that, with thermal physics working so much against it, a bass would resign itself to enduring whatever temperature comes along, be it hot or cold. After all, if you can't beat the system, why fight it? But that's not the nature of bass. Instead, they go out and find a temperature more to their liking.
Just as you and I may step inside a heated house to warm up, or move into the shade when we are too hot, fish continually move in and out of cooler or warmer water. For the heat-seeking bass, most times this means staying on the constant lookout for warmer waters.
Bass are rarely ever warm enough and would love a little extra heat. Wintertime bass tend to favor waters cooler than summertime bass, but both groups typically look for temperatures warmer than their surroundings normally provide.
Moreover, by spending time in warmer water, a winter bass steadily raises its temperature goal. Once that temperature is achieved, it looks for even higher temperatures. Followed long enough, this pattern ultimately brings the bass to a point where it finds the temperature it wants, in the area of 85-89°F where the bass metabolic machinery works at its optimal.
That's why in the springtime bass eagerly move into the shallows where the sun heats the water much faster than in the deeper sectors. It's also why winter-adapted bass, seeking respite from the icy cold, often congregate around the heated discharges of power plants where they spill into lakes or streams.
Not surprisingly, power plants are not operated to suit the fancy of the local bass population. Thus, when a plant requires an emergency shutdown, it does so regardless of the season. If the shutdown occurs during the summer months, no big deal. The resident bass in the outfall area adjust to a little thermal disappointment and go on with life. But during the winter months a plant shutdown can be catastrophic. Suddenly, and without warning, the bass are thrown into the icy waters of winter with no time to physiologically adjust. In these instances, the drastic temperature drops can have disastrous effects on bass health, even to the point of being lethal.
Which only goes to prove that old saying by Confucius: bass who cheats winter, soon finds himself in hot water.