Research Product

Concurrent daily measurements of environmental variables and embryo survival were made for two atherinid fishes, the California grunion, Leuresthes tenuis, observed at Blacks Beach, La Jolla, California; and the Atlantic silverside, Menidia menidia, observed at the Point of Pines, Edisto Island, South Carolina. Measurements were made during April 1980. Both species spawned in the upper intertidal zone on high tide. L. tenuis eggs were deposited approximately 4 cm below the beach surface during nighttime. Subsequent sand deposition buried embryos to a depth of approximately 8 cm where they were protected from thermal and desiccation stresses. Daily survival of incubating embryos averaged 97%. M. menidia utilized three spawning substrates: 1) abandoned crab burrows, 2) detrital mats, and 3) the stems and primary leaves of cordgrass, Spartina alterniflora. These substrates provided embryos with varying degrees of protection from thermal and desiccation stresses. Daily survival of embryos located 15 cm deep in abandoned crab burrows averaged 88%. Survival was less, 76% at the entrance. Daily survival averaged 94% at the surface of detrital mats and at the axis of stems and primary leaves of cordgrass. Survival was lower at other locations on these substrates.