Nekton use of regularly-flooded salt-marsh cordgrass habitat in North Carolina, USA

Abstract

Species composition, numbers and biornass of the nekton comn~unity on a regularly- flooded Spartina marsh near Beaufort, North Carolina, USA, was estimated for 1 yr using modified 10 m block nets. Thirty-five fish species dominated by mummichog Fundulus heteroclitus, spot Leiostomus xanthurus and pinfish Lagodon rhornboides were captured from the marsh surface. Numbers were greatest in April (1300 per 10 m of marsh edge); biomass was greatest in September (900 g per 10 m). Stream Order 1 (rivulet) marsh was occupied by fewer species, but contained greater numbers and biomass than Stream Order 3 (channel) marsh. (SAV) (however, estimates of these areas are not avail- able for comparison). An estimate of the species com- position, numbers and biomass of species using salt marsh habitat would be useful for habitat management and would enhance our understanding of the life his- tory of estuarine species. In this study, I sampled a saltmarsh for 1 yr to measure fish and macrocrustacean abundance, and to compare the nekton of 2 marsh microhabitats. STUDY AREA AND METHODS Collections were made from May 1986 to April 1987 in the lower Newport River estuary, N. Carolina, USA, in a 150 ha regularly-flooded, polyhaline marsh located 3 km from the Atlantic Ocean and 1 km north of Pivers Island (34"43' N, 76"40f W) (Fig. 1). Spartina alterniflora is the primary intertidal vegetation. The marsh is sur- rounded on 3 sides by channels with varylng water depths from 3 to 10 m and on the fourth side by a causeway. Two habitat types within a 250 m radius were sam- pled: channel-edge marsh and rivulet-edge marsh. This provided a 2 X 2 X 2 design: 2 habitat types, 2 locations for each habitat type, and a pair of plots at each location. Channel marsh sites bordered a third order tidal creek (Odum 1984). Water in front of this habitat never drained more than 1 to 2 m away from the vegetation at low tides. Rvulet marshes were at the