Bass are attracted to aquatic plants that grow in shallow water, including water willow, because of the food and cover they provide. But during the hottest summer days, an environmental condition makes them even more inviting.

Thermal or dissolved oxygen stratification occurs when the sun heats surface water to a point where it floats over cooler, denser, deeper water, according to biologist Mark Fowlkes of the N.C. Wildlife Resources Commission. 

“Once stratification occurs, a lot of the productivity is in this upper lighter layer,” he said. As that biological matter dies, it sinks into deeper water and decomposes, which depletes dissolved oxygen. Bass are then forced to the shallows, where the dissolved oxygen level is higher. 

Stratification occurs in some North Carolina lakes, though water inflow determines which ones, according to biologist Kinnon Hodges of the Commission. Smaller, riverine lakes usually have high inflow, which mixes the layers and dissolves any stratification. 

“Lookout Shoals Lake on the Catawba [River] is a good example,” he said, explaining that It only takes about nine days for water in the 1,300-acre lake to be completely exchanged, compared to more than 200 days on 32,500-acre Lake Norman.

Scott Lamprecht, an SCDNR biologist, has seen stratification in some Palmetto State lakes. 

“The bigger lakes aren’t as affected as the smaller ones,” Lamprecht said. In small ponds, he said, it’s typical to find all the fish in the top 4 feet of the water.