Identification of Eurasian watermilfoil using hydroacoustics

Successful Eurasian watermilfoil (Myriophyllum spicatum L.) management requires the ability to rapidly establish the presence and relative abundance of the plant. Using hydroacoustics (BioSonics DT-X equipped with a 430-kHz transducer), we have developed a method to quickly survey the littoral zone for the presence of Eurasian watermilfoil. The algorithm developed to interpret hydroacoustics data makes it possible to distinguish Eurasian watermilfoil from native species. Physical growth parameters, including depth, lateral extent, percentage of water column occupied by the plant, and other parameters are used to locate or identify the plant based upon hydroacoustics data. After establishing the ability to accurately identify milfoil quickly and effectively, the method was utilized in 5 bays in the southern end of Lake George, New York. Survey results identified 6 previously unknown Eurasian watermilfoil sites and confirmed the existence of an additional 10 known locations.