Calanoid recovery in Lake Reading eight years after termination of threadfin shad stocking.

Abstract

The Kansas Department of wildlife and Parks stocked threadfin shad (Dorosoma petenense) in Lake Reading, Kansas, each spring from 1980 through 1983. Introductions of this planktivore altered the calanoid population structure by reducing the length of the calanoid season and reducing the standing crops of Q. siciloides and D. pallidus. These changes resulted in D. pallidus replacing D. siciloides as the dominant calanoid species in this lake. The primary objective of this study was to determine if the D. siciloides population had recovered as the dominant calanoid. Nested ANOVAs and t-tests indicate that the D. pallidus population had recovered to pre-shad levels and that the ~. siciloides population had not recovered to preshad levels. Calanoid mean standing crops show that ~. pallidus outnumbered Q. siciloides overall during 1991-1992 sampling dates 15 to 1. Approximately 95% of adult calanoids identified in 1991 and 89% in 1992 were D. pallidus. Eight years after termination of the KDWP threadfin shad stocking project the length of the calanoid season was again similar to pre-shad levels. The~. siciloides population failed to recover as the dominant calanoid. Introductions of many new species of fish, higher fish densities, and the presence of another planktivore (gizzard shad, Dorosoma cepedianum) may have suppressed the Q. siciloides population.