Reproductive Rhythmicity of the Atlantic Silverside

Abstract

The reproductive periodicity of the Atlantic silverside Menidia menidia was studied at two locations on the North Edisto River estuary in South Carolina during March-July 1976–1978. Spawning runs occurred in the upper intertidal zone and coincided precisely with daytime high tides. Time-series analysis of daily changes in the intensity of spawning runs revealed a fortnightly reproductive periodicity and indicated that the observed reproductive rhythmicity in Atlantic silversides may be mediated by a high-tide-sunrise cue that also occurs at fortnightly intervals. During the 1976 and 1977 reproductive seasons, there were highly significant correlations (P < 0.01) among the male gonadal index, the female gonadal index, and the occurrence of intermediate, maturing, and hydrated-egg stages of sexual development in females. The percentage of females with hydrated eggs was greatest on days when a high tide occurred within 1 hour after sunrise.