Nekton use of vegetated marsh habitats at different stages of tidal inundation

Fishes and crustaceans are potentially important vectors for the transfer of production from intertidal marshes to subtidal estuarine environments. Because marsh habitats are accessible to nekton only when tidally inundated, understanding variation in habitat use associated with the tidal cycle is crucial for estimating the magnitude of production transfers attributable to nekton populations. We compared species richness, abundance and size distributions of nekton on inconung, slack high and ebbing stages of spnng tides at 2 vegetated intertidal marsh sites (25 and 90 m from the nearest tldal creek) on Sapelo Island, Georgia, USA. The findings showed how use of an intertidal marsh by nekton varied on temporal and spatial scales pertinent to understanding salt marsh community and ecosystem dynamics. A total of 9627 individuals distributed among l 7 species of fishes and 4 species of decapod crustaceans were collected from 60 samples of 100 m2 each during June to August 1991. The cypnnodontids Fundulus heterocljtus and F luciae accounted for 90.2"6 of all fishes; caridean Palaemonetes pugjo and penaeid Penaeus setiferus shrimps composed 99.8 % of the decapod crustaceans. In general, nekton abundance and species richness were greatest at slack high tide. In contrast to the depth distribution patterns usually observed at low tide, most of the smaller size classes of nekton that used the vegetated marsh at h ~g h tide were in the deeper site nearest the creek whlle larger size classes penetrated farther into the marsh interior The amount of intertidal marsh production transfered to subtldal estuarine habitats by different species of nekton may depend on how each responds, on balance, to the expanded foraging opportunity presented when the marsh floods and the risk of being stranded in the intertidal zone when the tide ebbs.