Hydroacoustic programs have been conducted on the Fraser River at Mission, B.C. by the International Pacific Salmon Fisheries Commission (1977-1985) and the Pacific Salmon Commission (PSC; 1986 to the present) to estimate gross upstream passage of Fraser River sockeye salmon. The estimates of daily salmon passage provided by the hydroacoustics program, combined with information from test fishery, stock identification, and catch monitoring programs are used in models to provide estimates of stock abundance, timing, and escapement that are vital to the in-season management of Fraser River Sockeye Salmon.
Following years of discrepancies between the Mission and spawning ground estimates investigations have been undertaken to determine the causes of the discrepancies between these two estimates. As part of the investigations into these discepancies DFO conducted a 5-year experimental program from 1993-1998 at Qualark Creek to design, test and perfect specialized in-river equipment and analytical protocols for riverine acoustic measurements. When Qualark was in monitoring mode in the 1990’s, the pattern of upstream passage tended to track that at Mission, but occasionally showed noticeable differences.
DFO reactivated the Qualark Hydroacoustic Site in 2008 to test the feasibility of the site for estimating salmon abundance with dual-frequency imaging sonar (DIDSON). The daily salmon flux has been estimated in-season using a DIDSON system on each bank of the river between 2008 and 2016. Assessing the performance of the Qualark program through these operational years, DFO has concluded that the site at Qualark is an excellent location for acoustic enumeration of salmon flux in the Fraser River. The site has the ideal characteristics for detecting and tracking Sockeye Salmon as they move upstream, and produces reliable in-season estimates of salmon flux.
Qualark’s sampling system includes 2 DIDSON acoustic units, deployed one on each bank of the Fraser River and operated 24 hours per day during the period of Sockeye Salmon migration. The sampling system also includes integration of catch data from the the daily test fishing operation conducted at the Qualark site on the Fraser River by the Yale First Nation. Daily salmon migration flux is derived by simple time expansion of sub-sampled salmon flux over 3 acoustic data range bins.