A seasonal field testing program was conducted during 1986 and 1987 to evaluate the effectiveness of behavioral barriers at Central Hudson Gas & Electric Corporation's Roseton Generating Station located in the euryhaline section of the Hudson River. This station was selected as representative of power plants with shoreline riverine/estuarine intake systems. Three commercially available devices (air bubble curtain, pneumatic gun, and underwater strobe light) were tested alone and in combination to determine their effectiveness in reducing impingement. The primary testing method incorporated three or four 6-h impingement collections during each test date, each consisting of two randomly assigned 3-h samples: one was an experimental tests with a behavioral device in operation, the other a control test with no device operating. The effectiveness of the devices at excluding fish was determined by comparing impingement data from experimental and control periods. Results of the program do not establish that the deployment of underwater strobe lights, pneumatic guns, and air bubble curtain, or various combinations of the three devices will effectively lower fish impingement at power plants similar in design and location to the Roseton plant. Deterrent effectiveness was found to be species-specific and related to time of day. http://www.epri.com