It takes a great deal of heat to make it change temperature. Large, deep bodies warm very slowly on spring days. Small, shallow areas, on the other hand, do so much more quickly, tough they cool down to lower temperatures at night. Thus spring comes to creeks and coves sooner than to the big rivers and the open Bay. The other factor results from spring's typically clear water, which sunlight penetrates readily.
Dark bottoms absorb the sunlight and radiate heat.
Things start to happen early in the upper tidal ends of the Bay's rivers. The perch have experienced serious water quality problems on a number of the Chesapeake s rivers in the past ten years, but in waterways that still have string runs, the fish are plentiful and beautiful. By the time of the yellow perch run, other fish are beginning to move around and feed actively. Knowledgeable anglers trying to cure cabin fever carry thermometers to raise the odds of finding warmed banks. Channel catfish feed in the deep holes.