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 exchanges for many resident and transient species. In many areas along the East Coast of the U.S. the dominant vegetation, Spartina alterniflora, has been replaced by the common reed (Phragmites australis). This shift has caused concern about the impact of Phragmites on marsh fauna but research in this area has been limited. During 1997 and 1998, we examined the effect of Phragmites 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 (rectangular 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 with Fundulus heteroclitus and Fundulus luciae significantly more abundant at Spartina sites. Fundulus heteroclitus was also the dominant fish (15-275 mm TL) collected in flumes but collections with this gear, including a number of species not collected in pit traps, showed no distinct preferences for different marsh vegetation types. Decapod crustaceans (1-48 mm CW) collected in pit traps were generally less abundant than fishes with Callinectes sapidus and Palaemonetes spp. most abundant in Spartina, while Rhithropanopeus harrisii was most abundant in Phragmites. The same decapod crustacean species (2-186 mm CW) dominated the flume collections and, similar to the pattern of fish collected by the flumes, there were no distinct habitat preferences for different marsh vegetation types. As a result of these observations, with different sampling techniques, it appears there is an overall negative effect of Phragmites on larval and small juvenile fish but less or no effect on larger fish and decapods crustaceans.