Improved Growth of a White Crappie Population following Stocking of Saugeyes (Sauger × Walleye): A Top-Down, Density-Dependent Growth Response

Abstract

The growth of white crappies Pomoxis annularis in Thunderbird Reservoir, Oklahoma, became unsatisfactory shortly after impoundment. Bottom-up strategies to improve growth (i.e., prey fish stockings) were unsuccessful. To increase predation on white crappies and elicit a density-dependent growth response, saugeyes (female walleye Stizostedion vitreum × male sauger S. canadense) were stocked annually from 1985 to 1996 and biennially thereafter. A 457-mm minimum length limit was placed on saugeyes to maintain high densities of adults. Annual trap-net samples revealed a reduction in abundance of stock-size (131–199 mm) white crappies and a concomitant increase in quality-size (200–249 mm) white crappies following establishment of the adult saugeye population. The mean length of white crappies of ages 1, 2, 3, and 5 increased after the saugeye population was established. Age-3 white crappies, on average, exceeded the 200-mm quality size from 1997 to 1999. The relative weights of stock-size white crappies increased, whereas those of quality-size white crappies declined after saugeyes were established. Saugeyes can reduce the abundance of small, slow-growing white crappies in southern impoundments. However, the possible effects of biomanipulations on all trophic levels in the affected system must be considered, and thorough evaluations should be done before and after such manipulations.