Temperature dependence of maximum daily consumption in white crappie: Implications for fisheries management

Maximum daily consumption (C-max) by adult white crappies Pomoxis annularis (164-532 g live weight) provided ad libitum rations of prey fish was determined at 18, 21, 24 and 27 degrees C. Observed increases in C-max between 18 and 24 degrees C followed by a sharp (two-thirds) decline at 27 degrees C indicated that a low to negative physiological ''scope for growth'' exists for white crappies at 27 degrees C and above. Examination of temperature and dissolved oxygen (DO) profiles from numerous Missouri impoundments for May-August 1991 suggested that white crappies were forced to occupy water of 27-32 degrees C (warm water) in 40% of these impoundments by early June and 85% by early August. White crappies were forced into warm water in only a slightly lower percentage of the deep (>5 m) impoundments we examined than in shallow (less than or equal to 5 m) ones. Evaluation of year-to-year differences (1988-1991) in time periods when white crappies were forced to occupy warm water in Lake Pomme de Terre, Missouri, showed that range (15-64 d) and time of occurrence varied substantially. Our findings suggest that the warm and annually variable summer temperature and DO regimes of many U.S. impoundments may substantially underlie the slow growth rates and among-year variation in size structure and recruitment that are characteristic of crappie populations in these environments.