Enumeration of Fall Chum Salmon Using Split-beam Sonar in the Chandalar River, Yukon Flats National Wildlife Refuge, Alaska, 2002-2006

摘要

A fixed-location split-beam hydroacoustic study was initiated in 1994 to assess the population abundance of adult fall chum salmon Oncorhynchus keta in the Chandalar River, a tributary of the Yukon River. Annual passage estimates have been made since 1995 and daily in-season counts have been provided since 1996. This report presents the results for the 2002 - 2006 seasons and describes the annual variability in run size and timing. Sonar operations began on August 8 and continued through September 26 for all years except 2004 when the sonar was shutdown 4 days early due to low water conditions. With the exception of 2002 and 2004, all years experienced periods of high water that interrupted data collection. Fall chum salmon passage estimates at the sonar site for 2002 - 2006 were: 89,580, 214,416, 136,703, 496,484, 245,090 respectively. These counts represent conservative estimates of total passage because they only include fish that passed during the dates of sonar operation. The passage rates on the first day of counting for all years were less than 0.8% of the total estimated count for that season. The passage rates on the final day of counting were less than 1.7% of the total estimated count for each year for all years except 2004 (4.6%). Median passage dates for 2002 - 2006 were: Sept. 12, Sept. 3, Sept. 7, Sept. 6, Sept. 6 respectively. Positional data suggested that most fish were detected by the sonar with few targets observed near the vertical or outer range limits of acoustic detection. Migrating chum salmon were shore-oriented and traveled close to the river bottom.