Influence of Gizzard Shad on Black Crappie populations in prairie impoundments of Western South Dakota

Abstract

Gizzard Shad Dorosoma cepedianum have been introduced into Western South Dakota reservoirs and shown to improve the growth and size structure of sportfish, particularly Walleye Sander vitreus. Black Crappies Pomoxis nigromaculatus are a popular sportfish in these reservoirs, but influences Gizzard Shad have on these populations have not been well documented. We used 10 years of annual sampling data to evaluate changes in Black Crappie population characteristics (i.e. recruitment, growth, size structure and condition) in four Western South Dakota reservoirs after Gizzard Shad were introduced. We also compared Black Crappie population characteristics after shad introductions to populations in three reservoirs never having shad. We found Black Crappie populations in Western South Dakota reservoirs are characterized by variable recruitment, generally experiencing some level of recruitment failure. Reservoirs with Gizzard Shad showed greater mean length-at-age and higher proportional size distributions (PSD and PSD-P) for Black Crappie after the shad introductions and higher values than observed in reservoirs never having shad. We found no meaningful differences in abundance, and mean condition of Black Crappie populations whether Gizzard Shad were present or not. The addition of Gizzard Shad did not appear to negatively affect Black Crappie populations but rather improved crappie size structure. Our results indicate that introductions of Gizzard Shad are a viable management option for producing quality Black Crappie fisheries in Western South Dakota reservoirs.