Growth of White Crappies in Response to Temperature and Dissolved Oxygen Conditions in a Kentucky Reservoir

Abiotic factors that may regulate growth, recruitment, and mortality of warmwater fishes in reservoirs of the Midwest and southeast United States are poorly understood. I examined the effect of reservoir temperature on the growth of white crappies Pomoxis annularis in a Kentucky reservoir to test the hypothesis that warm summer epilimnion temperatures may constrain white crappie growth and describe annual patterns of seasonal growth. Each year reservoir stratification reduced epilimnion volume as summer progressed and prevented white crappie use of cooler hypolimnetic waters due to low dissolved oxygen conditions below the thermocline. Water temperature at the 3‐m depth explained significant portions of variability in growth of both juvenile (age‐1) and adult (age‐2) white crappies during 1989–1993. Higher temperatures resulted in slower instantaneous growth rates, and growth usually decreased during Jul and Aug. Seasonal growth rates differed between juvenile and adult white crappies. Juveniles grew more rapidly than adults and completed most of their annual growth during April–Jul. Growth rates of adults peaked during Jun–Jul in 3 of 5 years and 1 and 2 months later during the other years. Minor length differences in April among five year‐classes of each age did not result in growth advantages during April–Oct. Some somatic growth was detected during Oct–April for three of four year‐classes. These results supported the hypothesis that typical summer temperatures in some warmwater reservoirs may suppress growth of white crappies. Defining relations between seasonal growth patterns and water temperature and dissolved oxygen conditions in reservoirs will help set expectations for fisheries and provide direction for management strategies.