copied info i found:
The primary peacock bass study area was restricted to the coastal, man-made canal system of eastern (urban) Dade County. Peacock bass are incapable of tolerating water temperatures less than 60 degrees F, and the deep canals that were primarily constructed for drainage and flood control purposes seldom fall below 70 degrees. These canals are cut into the Biscayne Aquifer which is a shallow water table aquifer that offers spring influence.
Winter temperatures in natural Florida waters nearly always drop below 60 degrees F, except in ground water springs. In the eight years that Shafland has monitored water temperatures in the canal system, the coldest he's seen was 66 degrees. The warm waters are vital to the peacock bass over-wintering in the expansive waterway.
"The box-cut canals expose relatively small amounts of the waters to the weather," explains Shafland. "Probably just as important is the surficial aquifer, which allows underground water to flow from west to east. During the winter, storm water is stored in the East Everglades and that puts more head pressure. which causes a little underground flow into the canals."
If you swim in the canals, you can feel places where the warm water is coming in during the winter, according to the biologist. During cold fronts, some movement of the peacock bass is associated with water temperature. During a critical point when they begin to become stressed, they will seek out warmer water nearby.
The temperature limits their distribution in Florida, but it is also a safety factor, which prevents them from spreading to all waters around the state. The salinity tolerance limitations are similar to that of the largemouth bass. That gave the Commission assurance that the fish was safe and would be limited to the target area, the Southeast Florida canals only.