The Hudson River was once known as a nursery for large numbers of anadromous fishes including American Shad, Alewife (Alosa pseudoharengus), Blueback Herring (Alosa aestivalis), and Striped Bass (Morone saxatilis). Currently, American Shad stocks in the Hudson River and along the Atlantic coast are at an all-time low, and there is concern that stocks may not recover naturally. In addition, Striped Bass stocks have recently been in decline, although these stocks are still considered to be in good condition. Because spawning timing and duration of several fish species are directly related to water temperatures, looking at long-term temperature data allows for an examination of trends in reproductive temporal scale. In this study, we investigate changes in spawning phenologies of American Shad and Striped Bass over time in order to determine if temperature changes can explain some of the recent declines in these species. A model is developed to predict future temperature changes in the Hudson River estuary in order to predict the likelihood of spawning failure of the signature fishes of the Hudson River.