Research Product

The reproduction ecology and spawning periodicity of the Atlantic silverside, Menidia menidia, was studied in the North Edisto River estuary, South Carolina, at Bears Bluff and the Point of Pines during the spring and summer, 1976-1978. Spawning runs occurred only in daytime and coincided precisely with the predicted time of high tide. Spawning by large numbers of fish in a small area at high tide, when tidal current and velocities were low, caused depletion of dissolved oxygen to more than l.0 mg/l. M. menidia spawned in the upper intertidal zone at elevations of 1.20 to 2.40 meters above mean low water. Observed maxima in spawning-run index values occurred near the time of new and full moons, suggesting that the spawning population is synchronized by a lunar cue. The coincidence of a high tide at the time of sunrise every two weeks (high tide-sunrise cue) also may have served as a synchronizer for the spawning population. Determination of the relative importance of each factor was made difficult by their approximate synchrony during the March-July spawning season. Many predators fed on spawning M. menidia. Several predators, including the ruddy turnstone, Arenaria interpres morinella, semipalmated sandpiper, Ereunetes pusillus, and blue crab, Callinectes sapidus, fed on developing M. menidia embryos. Larval emergence was limited to times of tidal inundation. More larvae hatched during high tides at night than during the day.