Effects of Shad Density and Reservoir Hydrology on the Abundance and Growth of Young-of-Year Crappie in Alabama Reservoirs

ABSTRACT

We studied five Alabama reservoirs during 1992 through 1994 to explore the influence of both reservoir hydrology and larval shad (Dorosoma spp.) on young-of-year crappie (Pomoxis spp.) recruitment. Mean relative abundance of age-0 crappie was slightly and negatively correlated with larval gizzard shad (D. cepedianum) density but not with that of larval threadfin shad (D. petenense). Alternatively, age-0 crappie growth was positively correlated with threadfin shad density but not with gizzard shad density, which indicated that shad were not adversely affecting young crappie growth via competition for food. Neither crappie abundance nor growth was related to the dates of peak larval gizzard shad or threadfin shad occurrence. Age-0 crappie abundance was positively related to mean summer (June-August) retention time in four short retention time (< 15 d) reservoirs. However, when gizzard shad density was included into the analysis, this variable was no longer a significant predictor of crappie abundance, indicating that the relation between larval gizzard shad density and age-0 crappie abundance was overridden by the influence of mean summer retention time. Our findings indicate that the potential for interactions between young crappie and shad is certainly viable, but any impacts that larval shad might have had on age-0 crappie abundance and growth were not detected.