TEMPERATURE-DEPENDENCE OF MAXIMUM DAILY CONSUMPTION IN WHITE CRAPPIE - IMPLICATIONS FOR FISHERIES MANAGEMENT

Maximum daily consumption (C-max) by adult white crappies Pomoxis annu laris (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) dec line 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 n umerous 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. Wh ite crappies were forced into warm water in only a slightly lower perc entage of the deep (>5 m) impoundments we examined than in shallow (le ss 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 t hat the warm and annually variable summer temperature and DO regimes o f many U.S. impoundments may substantially underlie the slow growth ra tes and among-year variation in size structure and recruitment that ar e characteristic of crappie populations in these environments.