The Yukon River Border Sonar Program

Alaska Department of Fish and Game (ADF&G) and Fisheries and Oceans Canada (DFO) actively manage Chinook and chum salmon fisheries in the Yukon River drainage. According to the Yukon River Salmon Agreement, Alaska is obligated to manage Yukon River salmon fisheries with a view to delivering an agreed spawning objective plus the Canadian guideline harvest to the Alaska-Yukon border. A daily estimate of salmon crossing the border between Alaska and Canada is crucial to meeting the obligations laid out in the Yukon River Salmon Agreement. Until 2005, DFO provided the only estimate of mainstem salmon passage across the Alaska/Canada border through a mark and recapture study. In 2003, ADF&G carried out a study to identify a suitable location to estimate the daily and seasonal passage of adult Chinook and fall chum salmon using hydroacoustic techniques. It was found that Six-Mile Bend approximately 11.5 km downriver of Eagle Alaska was an excellent site with linear bottom profiles on both sides of the river without large obstructions; a single channel; available beach above water level for topside equipment, and sufficient current, i.e., areas without eddies or slack-water. In 2005, a full-scale sonar project was conducted to estimate Chinook salmon passage using DIDSON on the right bank and split-beam sonar on the left bank, and to use gill net sampling to estimate run timing and characterize age and sex composition of the Canadian bound fish. The project duration was extended in 2006 to also provide an estimate of fall chum salmon passage. Split-beam and DIDSON technology have been used each year since then to estimate Chinook and chum salmon bound for Canadian waters. ADF&G and DFO share joint responsibility for project cost and operations. There has been productive bi-lateral cooperation and consultation throughout the development of this project, leading to increased confidence in, and agreement upon, salmon border passage estimates.