Abstract
This study investigates the influence of Phragmites australis (common reed) invasion on the habitat of the resident marsh fish, Fundulus heteroclitus (mummichog) in the Hackensack Meadowlands, New Jersey. These abundant fish play an important role in the transfer of energy from the marsh surface to adjacent subtidal waters and thus estuarine food webs. The objectives of this 2-yr study (1999 and 2000) were to compare the distribution and abundance of the eggs, larvae, juveniles, and adults of mummichog and their invertebrate prey inhabiting Spartina alterniflora-dominated marshes with Phragmites-dominated marshes, and to experimentally investigate the influence of marsh surface microtopography on larval fish abundance within Phragmites-dominated marshes. In 2000, we verified that egg deposition does occur in Phragmites-dominated marshes. In both years, the abundance of larvae and small juveniles (4-20 mm TL) in S. alterniflora was significantly greater than in Phragmites-dominated marshes, while larger juveniles and adults (> 20 mm TL) were similarly abundant in both habitat types. The overall abundance of larvae and small juveniles was significantly greater in experimental Phragmites plots in which microtopography was manipulated to resemble that of Spartina marshes than in Phragmites control plots. Major groups of invertebrate taxa differed between marsh types with potential prey for larval fish being significantly more abundant in S. alterniflora marshes. Phragmites-dominated marshes may not provide the most suitable habitat for the early life-history stages of the mummichog. The low abundance of larvae and small juveniles in Phragmites marshes is likely due to inadequate larval habitat and perhaps decreased prey availability for these early life history stages.