Alosines are fishes of the subfamily Alosinae, commonly called shads, of the herring family (Clupeidae). This document reviews the biology and ecology of the four anadromous alosines in the Chesapeake Bay ecosystem. The anadromous alosines of the Chesapeake Bay are American shad Alosa sapidissima, hickory shad Alosa mediocris, blueback herring Alosa aestivalis, and alewife Alosa pseudoharengus (Murdy et al. 1997). As anadromous fish, they live most of their life at sea, where they mature, and return to freshwater habitats to spawn. The value of a species can be measured both by what is gained by its presence and lost by its absence. Historically, these alosines were among the most abundant and economically valuable fishes of the Chesapeake Bay (Loesch and Atran 1994; Hildebrand and Schroeder 1928); however, today they are largely regulated by a moratorium on directed fishing (Markham and Weinrich 1994; Olney and Hoenig 2001). Their serial decline in abundance, for more than a century, has left their fisheries in dismal shape and has threatened their prominent contribution to American heritage (Limburg and Waldman 2009).