Fraser River Sockeye Fisheries and Fisheries Management - Cohen ...

ecommendations by the Mission Hydroacoustic Facility Working Group (1994), PSCand DFO formed a joint research program to examine various assumptions about fishbehaviour associated with the single-beam abundance-estimation model (Banneheka et al.1995). The quantitative results from these studies answered key questions and resultedin the development of a new estimation model (Xie et al, 1997, and Xie et al, 2002, Xie2002). From these findings, the PSC-DFO Hydroacoustic working group concluded that asplit-beam sonar system would be a more reliable and robust estimator for estimatingsalmon passage at the Mission site.From 1999-2002, a Phase 2 study demonstrated that the split-beam technology andestimation model could be implemented at the site. In 2003, the split-beam estimator wasfirst put into operational phase during the field season to test the ability of the system toprovide real-time information for in-season management. The results were satisfactoryand, the Fraser River Panel approved the implementation of the split-beam system as theprimary estimator of abundance for the in-season management of Fraser River sockeye in2004. A major change to the sample methods was associated with the change intechnology; in addition to a transecting vessel, a fixed shore based sampling platform wasestablished on the south bank.In 2004-2005, the Southern Boundary Restoration & Enhancement Fund (SEF) providedfunding for a project to investigate the use of Dual-Frequency Identification Sonar(DIDSON) to examine fish behaviour in the Fraser River. This project verified many ofthe assumptions of, and estimates of daily salmon flux by the current split-beam estimator(described in detail in Xie et al 2005). It also indicated that DIDSON technologies couldprovide reliable estimates of daily salmon passage in near-shore areas of the river.Finally, since 2005, a stationary split-beam system similar to that on the south bank wasdeveloped and implemented on the north bank.Due to the large sampling fractions, precision of estimates is already very high(Banneheka et al. 1995; Xie et al. 2005). However, two sources of potential bias remainin the estimation of sockeye daily abundance: (1) the mobile portion of the estimator, as itrelies on the statistics of fish behaviour from the shore-based split beam systems and isalso subject to possible negative bias as a result of salmon avoiding the transectingvessel; (2) Estimation of species composition of the salmon migration upstream.In March 2006 the PSC sponsored a workshop on the application of hydroacoustics forsalmon management (PSC 2007). This workshop was part of an initiative sponsored bythe SEF Committee which had requested that a group be formed to develop a StockAssessment Framework for Fraser River sockeye in 2006.J-2