Largemouth Bass Hatching Success and First-Winter Survival in Two Illinois Reservoirs

Abstract

Water level regimes affected periodicity of hatching success of largemouth bass Micropterus salmoides in two central Illinois reservoirs, Carlyle Lake and Lake Shelbyville. Periodicity of hatching success was determined from daily rings on otoliths of young-of-the-year largemouth bass collected each July during 1988–1990. Hatching success was disrupted during rapid water level rises and drops. Peak hatching success occurred when water levels were relatively stable. No relationship existed between timing of peak hatching success and abundance or sizes attained in first year. Little evidence was found for size-related winter mortality. Largemouth bass recruitment was considerably higher in high-water years than in low-water years, and appeared to be unrelated to water level fluctuations during the spawning season. However, we suggest that water-level-influenced hatching disruptions could be critical to year-class strength if water levels were to fluctuate over most of the spawning season.