- Noimative invasive species pose a growing threat to living aquatic resources in the United States. Shipping particularly use of ballast water represents a major pathway of introduction for these species and in 1996, Congress established a program of baseline surveys to measure the effectiveness of ballast water management. This report describes a three part project: a literature survey conducted to help identify native and non-native species present in the Middle Columbia and Lower Snake Rivers; an investigation of ship and barge ballasting practices on the rivers; and an evaluation of whether baseline surveys are appropriate measures of successful ballast water control. The first part of the project entailed a comprehensive literature review for the Middle ColumbialLower Snake Rivers Aquatic Nonindigenous Species Survey (MCRANS) which will be used to help establish a baseline for the presence of both native and non-native species in the main stems of the Middle Columbia and Lower Snake Rivers, and to assist in the development of a field sampling plan to monitor for potential introductions of nonindigenous species to these waters. Technical project reports, collection records, databases, and "gray literature" from various federal, state, and local agencies, academic institutions, and industries were researched to compile the lists of species present in the system. A listing of 781 organisms was tabulated from these resources, of which approximately 377 distinct organisms were identified to at least genus level, and of these 377, 44 were identified as nonnative to the system. During the MCRANS literature review, several papers were discovered in which appearances or discoveries of new species in various stretches of the rivers were attributed to introductions via ballast waters from tug and barge traffic. The second part of this project entailed an investigation of ballasting procedures by commercial tug and barge companies, governmental shipping contractors, and commercial cruise line companies. However, interviews revealed that river tugs and barges do not routinely take on or discharge ballast waters during shipping operations as was widely believed outside of the shipping industry. The one exception involves Navy barges which carry spent nuclear reactors (and possibly ballast water) from the Puget Sound Naval Shipyard up the Columbia River to the Port of Benton, in Richland Washington, where they undertake limited ballasting operations while unloading their cargo. Review of other baseline surveys revealed ambiguities that make pathway assignments for ANS difficult, including inconsistent methods and terminology used for monitoring, sampling and identification, uneven temporal and spatial distribution of surveys, and apparent spikes in vectors that may simply reflect increases in strengths of sampling efforts. Finally, this project resulted in the recognition that creation of a group or task force, focused on ANS issues in the Columbia River basin, is needed to Enhance regional coordination and collaboration for ANS monitoring and research, and for management of ANS pathways related to Columbia River shipping activities.