Tag Archives: outmigration

Continuing the evaluation of abundance and stock composition of downstream migrating juvenile Sockeye Salmon in the lower Fraser River

While Fraser River sockeye salmon survival has declined over the past decade, it has also exhibited high interannual variability. The processes responsible for this trend and the variability are not understood and require investigation. This project builds on the previous work by adding a fifth year of sampling juvenile migrants immediately prior to their entry into the Strait of Georgia (SoG). The sampling platform will be identical to that employed successfully in 2013-2015, and GSI analysis will help to provide estimates of relative abundance and migration timing past Mission by stock. It is anticipated that sampling intensity in 2016, a juvenile Pink Salmon outmigration year, will be similar to that in 2014. In 2016, we propose to repeat the 2014 & 2015 study design and parameters assessed, including the assessment of the nocturnal migration patterns of Sockeye juveniles for a third year.
As in previous years, samples collected under this project will be compared to samples collected in other ongoing and proposed assessments, such as DFO’s annual SoG trawl survey occurring June-July and a similar trawl survey in Johnstone Strait. In combination, these three studies will add a third year to a comprehensive multi-stock assessment of Fraser River juvenile sockeye salmon relative abundance and condition, from nursery lake exit through early marine near-shore residency.
Sub-yearling ocean-migrant sockeye salmon (e.g. Harrison River stock) can be important contributors to Fraser River Sockeye production. The 2016 survey will continue to incorporate the bio-sampling of captured sub-yearling juveniles to identify their contribution, and migration timing at Mission by Conservation Unit (CU).
Lastly, the 2016 project will explore the feasibility of deploying an acoustic Doppler current profiler in an attempt to measure water current velocities over a depth range. This information may be important in determining absolute juvenile sockeye abundance at Mission.

Migration Timing of Juvenile Fraser River Sockeye in Johnstone Strait

In 2014, Fisheries and Oceans Canada proposed a 3-year program to evaluate the effect of smolt size and age on the migration timing of Fraser River Sockeye Salmon out of the Strait of Georgia by conducting a weekly sampling program in southern Johnstone Strait with a purse seine. We proposed to use DNA analyses to infer stock-specific migration timing through this area and, combined with the sampling in the Lower Fraser River (Evaluation of abundance and stock composition of downstream migrating juvenile Sockeye Salmon in the lower Fraser River), provide accurate estimates of residence time within the Strait of Georgia at the Conservation Unit (CU) level. In addition, by examining changes in the relative abundance of different CUs between the lower Fraser River and Johnstone Strait, this study was expected to determine whether mortality rates differ among CUs within the Strait of Georgia. In addition, we proposed to assess the feasibility of using hydroacoustics as a tool to monitor how the abundance of juvenile Salmon changes over time in this area.