This 1999 USGS research report by Alex Haro and others was produced in response to the possible decline in American eel populations. Prompted by the lack of information on the behavior of downstream migrant eels at hydroelectric dams and other obstructions, researchers used hydroacoustic monitoring to attempt to monitor "the spatial and temporal patterns of behavior of large (> 70 cm) eels in hydroelectric forebays." The report may be browsed online or downloaded as a self-extracting file (1300K).