Effects of common reed (Phragmites australis) invasion on marsh surface macrofauna: Response of fishes and decapod crustaceans

The tidally inundated marsh surface is an important site for energy exchang es for many resident and transient species. In many areas along the East Co ast of the U.S. the dominant vegetation, Spartina alterniflora, has been re placed by the common reed (Phragmites australis). This shift has caused con cern about the impact of Phragmites on marsh fauna but research in this are a has been limited. During 1997 and 1998, we examined the effect of Phragmi tes on fish and decapod crustacean use of the marsh surface in the brackish water reaches of the Mullica River, in southern New Jersey, U.S. Fish and decapod crustaceans were sampled with an array of shallow pit traps (rectan gular glass dishes, 27.5 x 17.5 x 3.7 cm) and with flumes (1.3 m wide x 10 m long of 3.2-mm mesh). Fish (2-60 mm TL) dominated pit trap collections wi th Fundulus heteroclitus and Fundulus luciae significantly more abundant at Spartina sites. Fundulus heteroclitus was also the dominant fish (15-275 m m TL) collected in flumes but collections with this gear, including a numbe r of species not collected in pit traps, showed no distinct preferences for different marsh vegetation types. Decapod crustaceans (1-48 mm CW) collect ed in pit traps were generally less abundant than fishes with Callinectes s apidus and Palaemonetes spp. most abundant in Spartina, while Rhithropanope us harrisii was most abundant in Phragmites. The same decapod crustacean sp ecies (2-186 mm CW) dominated the flume collections and, similar to the pat tern of fish collected by the flumes, there were no distinct habitat prefer ences for different marsh vegetation types. As a result of these observatio ns, with different sampling techniques, it appears there is an overall nega tive effect of Phragmites on larval and small juvenile fish but less or no effect on larger fish and decapods crustaceans.