The Alaska Department of Fish and Game first installed sonar to count Chilkat sockeye salmon in 2007 and collected its first full year of data in 2008. The Chilkat sonar project site uses a type of sonar technology known as DIDSON. Before sonar, ADF&G monitored Chilkat sockeye salmon escapement using a weir. Sonar has improved escapement estimates by enabling ADF&G technicians to monitor escapement uninterrupted, even during flow reversal, severe whether events and periods of high boat traffic or turbidity.
Technicians still install the weir each year, but instead of using it to block fish passage for visual counting they install it as a tool to funnel salmon within the DIDSON’s detection range. Technicians install a single DIDSON unit along the upstream edge of a 33-foot gate opening in the weir. Technicians also used the weir to help them collect fish samples. (See Other Tools)
Sonar site operations begin June 7 and continue until mid-October.