Restoration of American shad Alosa sapidissima populations in the Susquehanna and Delaware Rivers, USA

Historically, both the Delaware and Susquehanna Rivers were major producers of American shad Alosa sapidissima on the Atlantic coast of the United States. However, significant environmental problems led to the virtual extirpation of American shad in the Susquehanna River and a severe population reduction in the Delaware River stock. The Susquehanna shad population was lost due to the construction of four large hydroelectric dams in the lower 90 km during 1904-1931. Fish re-introduction and project evaluation activities have been undertaken over a three-decade period by numerous state, federal, and utility company partners. These activities included the culture and release of over 150 million marked larval and fingerling shad, and trap and transport of over 200,000 pre-spawned adults to suitable spawning waters above blockages. The shad population returning to the lowermost dam on the Susquehanna grew from only a few hundred to over 200,000 fish in the past 17 years. Survival of out-migrating juvenile shad through hydroelectric turbines has been evaluated and, where necessary, improved with project operational changes during peak movement periods. Settlement agreements reached with each of the utility companies led to construction of large capacity fish elevators and ladders at the four lower river dams during 1991-2000.