The influence of contiguous shoreline type, distance from shore, and vegetation biomass on nekton community structure in eelgrass beds

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Three factors affecting the structure of nekton communities (fishes and decapod crustaceans) in eelgrass beds were identified and evaluated: contiguous shoreline type, distance from shore, and macrophyte biomass. Throw traps (1 m2) were used to sample eelgrass nekton at seven locations in Great South Bay (New York, U.S.) along Fire Island National Seashore from May through October 1995. Abundances of Gobiosoma ginsburgi, Apeltes quadracus, and Opsanus tau were significantly higher in eelgrass beds adjacent to salt marshes. Menidia menidia, Syngnathus fuscus, Pseudopleuronectes americanus, and Palaemonetes pugio were significantly more abundant in eelgrass adjacent to beaches. Regression analyses indicated that Syngnathus fuscus, Pseudopleuronectes americanus, and Anguilla rostrata abundances were positively related to eelgrass biomass, and Apeltes quadracus and Gobiosoma ginsburgi abundances were highest at moderate levels of macroalgae biomass. The distance of an eelgrass bed from shore was also important. Species generally associated with salt marshes (Fundulus heteroclitus, Cyprinodon variegatus, Lucania parva, and Palaemonetes pugio) were more abundant in eelgrass near the marsh shore. Abundances of Apeltes quadracus, Syngnathus fuscus, Menidia menidia, Hippolyte pleuracanthus, and Crangon septemspinosa increased with distance from the shoreline. Shoreline type, distance from shore, and macrophyte biomass appear to affect the abundance and distribution of some nekton species. The effect of shoreline type may be related to the distribution of macrophyte biomass; the biomasses of eelgrass and macroalgae were significantly higher along beach and marsh shorelines, respectively. Explaining within-habitat variability and identifying micro-habitat preferences for nekton will aid in the proper design of future studies and habitat restoration efforts.

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