19 Cohen, A. N. Carlton, J. T. 1996 Executive Summary: Nonindigenous Aquatic Species in a United States Estuary: A Case Study of the Biological Invasions of the San Francisco Bay and Delta, reprinted in National Invasive Species Act of 1996 Hearing before the Subcommittee on Drinking Water, Fisheries and Wildlife of the Committee on Environment and Public Works, U. S. Senate, 104th Congress, Second Session on S. 1660, U. S. GPO, Washington, July 17, 1996 pp. 178-185 BI