RT Book, Whole DB /z-wcorg/ DS http://worldcat.org ID 70668433 LA English T1 Sonar estimation of chum salmon passage in the Aniak River, 2003 A1 Sandall, Heath D., Pfisterer, Carl T., Alaska., Division of Sport Fish., Alaska., Division of Commercial Fisheries., PB Alaska Dept. of Fish and Game, Division of Commercial Fisheries [i.e. Sport Fish], Research and Technical Services PP Anchorage YR 2006 AB The Aniak River sonar project has provided daily fish passage estimates for most years since 1980. During this time, the project has undergone important changes including changing from the original Bendix sonar to dual-beam and is in the process of migrating to a high frequency imaging sonar (DIDSON). This season, the project adopted a new sampling protocol in which the sonar operated for three 4-hour blocks each day (0000-0400, 0800-1200, and 1600-2000 hours). The Aniak River sonar project was operational from 28 June through 31 July in 2003. During this period, an estimated 393,396 fish (SE 7,871) passed through the ensonified area. The peak passage of 23,208 fish occurred on 14 July and the 50% passage date occurred on 17-July. The escapement estimate was primarily comprised of age-0.3 fish (80.6%), while age -0.4 (17.9%), -0.5 (1.1%) and -0.2 (0.4%) classes were also present. Side-by-side comparisons of counts obtained with the BioSonics and DIDSON equipment suggest undercounting with the BioSonics at high densities.