in the Hudson River are not in the river long enough to be affected by PCBs and other contaminants (however, fishing for or possessing American shad [including catch and release] in the Hudson River or Marine District is now prohibited). Pollution, however, may impact shad reproduction and studies have been undertaken to determine whether fingerlings suffer DNA damage. Most of the rivers across the historic range of shad are now heavily dammed, eliminating many of the spawning grounds. For example, the number of shad harvested in the Merrimack River declined from almost 900,000 in 1789 to none in 1888, likely due to the inability to reach their spawning ground following a period of heavy dam construction. Since then, fish passage efforts have begun to remedy this situation, including the Chesapeake Bay program. While recreational angling has almost no measurable impact on shad populations, they are susceptible to commercial overfishing. Because of their highly migratory life history and their recreational and commercial importance, American shad are co-managed by the U.S. Fish and Wildlife Service, the National Marine Fisheries Service, and state fisheries agencies. The Atlantic States Marine Fish Commission serves as a key forum for coordinating the collective effort to conserve American shad. Introduced in the North Pacific American shad were introduced into the San Francisco Bay/Sacramento River system in California in the 1800s, and they have spread throughout many river systems on the West Coast of North America. A large shad population occurs in the Columbia River. In recent years, shad counts at Bonneville and The Dalles Dams have ranged from over two million to over five million fish per year. Spawning shad return to the Columbia in May and June and migrate above Lower Granite Dam on the Snake River and above Priest Rapids Dam on the Upper Columbia. Unlike many introduced species, American shad have not been confirmed to have serious negative effects on the environment or other native fish species in the Columbia. American shad are also occasionally found on the Northwest Pacific coast in Kamchatka, Russia. Shad fishing Shad are also valued as a sport fish that exhibit complex and little-understood feeding behaviors while spawning. Unlike salmon, shad retain the ability to digest and assimilate food during the anadromous migration. Like other fish, their feeding instinct can be triggered by a variety of factors such as turbidity and water temperature. Society and culture Shad serve notable