Developing models in support of ecosystem-based management requires knowledge of trophic dynamics of ecologically important species. A paucity of data on these dynamics for Long Island finfish is hindering development of ecosystem models required by recent legislation. In this study, we analyzed stomach contents of common fishes collected from Port Jefferson Harbor, Great South Bay, and Shinnecock Bay between May and October of 2007 and 2008. General diet composition was described by percent by number (%N), percent by weight (%W), percent frequency of occurrence (%0), and percent index of relative importance (%IRI) for seven species: Paralichthys dentatus (Summer Flounder), young-of-the-year (YOY) Pomatomus saltatrix (Bluefish), Prionotus evolans (Striped Searobin), Stenotomus chrysops (Scup), Scophthalmus aquosus (Windowpane Flounder), Raja eglanteria (Clearnose Skate), and Morone saxatilis (Striped Bass). Temporal diet composition was estimated for the consistently abundant YOY Bluefish, Summer Flounder, and Scup, where most n_season > 25. Subsampling of large catches of YOY Bluefish and Scup led to investigation of diet composition by cluster sampling. Important prey included Crangon sp. (sand shrimp), Cancer irroratus (Rock Crab), and forage fishes. Pseudopleuronectes americanus (Winter Flounder), once a common prey item in stomachs of piscivorous Long Island fishes, contributed ≤ 6.7 %O and ≤ 1.6 %W to the diets of Summer Flounder, Striped Searobin, Striped Bass, and YOY Bluefish. These changes may be due to shifts in the abundance of prey items or changes in spatial overlap of predator and prey.