Trophic dynamics and habitat ecology of the dominant fish of Delaware Bay (United States of America) marsh creeks.

摘要

Delaware Bay's extensive salt marshes serve as foraging habitat for the juveniles and later life stages of numerous fish species, including many of recreational, commercial and ecological importance. I examined the seasonal occurrence and trophic dynamics of six numerically dominant fish species ( Cynoscion regalis, weakfish; Leiosfomus xanthurus, spot; Micropogonias undulatus, Atlantic croaker; Morone americana, white perch; Morone saxatilis, striped bass; and Anchoa mitchilli, bay anchovy) using salt marsh creeks at five marsh sites located along the New Jersey coast of the bay. The goals of this research included determining the relative value of the sites as foraging habitat and assessing ontogenetic, seasonal and geographic trends in the food habits and trophic ecology of these species.; All species underwent ontogenetic changes in their food habits, generally corroborating the results of earlier studies with notable differences, perhaps due to the location of the current study, methodological differences that made this study more accurate, or a combination of factors. An analysis of geographic patterns of abundance and stomach fullness indicated that marine transient species appeared to recruit preferentially to sites of high resource abundance in the lower bay while the resident M. americana was restricted by physico-chemical tolerance to limited nurseries in the upper bay where it may have experienced intraspecific resource competition.; The seasonal timing of entry, residence and exit from the sites by the transient species was highly staggered and the fish often showed strong trophic niche partitioning when they did co-occur, suggesting an assemblage that has been shaped by natural selection to avoid resource competition and thus contradicting many previous studies that have concluded that young fish using salt marshes are trophic opportunists that share abundant resources.; One of the marsh study sites was a former salt hay farm that underwent restoration one year before my study commenced. Fish abundance, stomach fullness, diet composition, fish condition (indicated by weight-at-length) and tidal feeding periodicity were all at least similar at the restored and reference site, and were often found to be enhanced at the restored site, leading to the conclusion that the restored marsh was providing suitable fish foraging habitat.