Feeding Behavior of American Shad during Spawning Migration in the York River, Virginia

—Throughout its native range, American shad Alosa sapidissima is thought to cease feeding during anadromous migration. We examined the feeding habits of American shad during spawning migration by documenting changes in diet composition and feeding that occur in mature fish in the York River, Virginia. American shad were collected prior to and after spawning at various locations on a gradient from open ocean waters to the freshwater spawning grounds. During the estuarine phase of migration, American shad fed predominantly upon mysid shrimp Neomysis americana and calanoid copepods. Feeding occurred during prespawning migration but decreased on the spawning grounds where plant matter comprised the majority of the stomach contents. After spawning, feeding intensity increased significantly as American shad resumed feeding on mysid shrimp and copepods during downstream migration through estuarine waters. Comparisons of diet composition and feeding intensity between the oceanic environment and the estuary indicate that calanoid copepods and planktonic shrimp dominated the diet in both environments, although feeding intensity was reduced within the estuary during the spawning migration. These results indicate that American shad in the York River feed during anadromous migration, most heavily in the middle estuary where there is an abundance of mysid shrimp. While shad lose somatic weight during migration, indicating insufficient consumption to maintain body condition, the ability to feed during some portion of migration and then soon after spawning may be important in decreasing postspawning mortality.