Growth of White Crappie and Channel Catfish in Relanon to Varianons in Mean Annual Water Level of Lake Carl Blackwell, Oklahoma

Variations in annual increments of growth of white crappie. Pomoxis annularis Rafinesque, and channel catlish, Ictalurus punctatus (Rafinesque), are examined in relation to mean annual water level of Lake Carl Blackwell, 1962-1967, when lake level was declining. The occurrence of lee's phenomenon precluded a correlative comparison of white crappie growth with water level, but decrease in growth at age I and the increase at older ages is attributed to the decline in water level. The crappie body-scale relationship changed from curvilinear to linear as growth improved during the drawdown period. Correlations of channel catfish growth with lake level were significant for age 1 (r= -0.84, P 0.05), age 2 (1'= -0.92, P 0.0 I) and age 6 (1'= -0.81, P 0.05). We hypothesized that the declining water level increaded the growth of channel catfish through reduced intraspecific and interspecific competion. The reduction in competition is believed to result from decreased spawning success and increased predation upon small channel catfish by piscivorous fishes such as largemouth bass and flathead catfish.

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