By Todd Driscoll
Texas Parks and Wildlife Department

Most anglers have likely heard the words "thermocline" and "turnover" associated with local fishing reports and dock talk at tackle shops. Both result from thermal stratification, which is an annual occurrence at a majority of southern reservoirs. As part of the stratification process, reservoirs develop pronounced temperature barriers (thermoclines) and anoxic zones (water without oxygen) in the summer and “turnover” or mix during the fall. Many bait fish and sport fish relate to the thermocline during summer, as it contains the coldest water with adequate oxygen levels. Anglers can put more fish in the boat by better understanding the predictable process of stratification.