The purpose of this project was to continue the development of lower river live capture, tagging and sampling facilities that would, in conjunction with catch monitoring and hydroacoustics, provide reliable species specific estimates of abundance for salmon returns to the Fraser River. A combination of annual mark-recapture efforts using conventional external tags and periodic radio-telemetry studies to assess mark-recapture assumptions and the nature of any in-river losses could provide managers with more reliable estimates of spawning escapement, harvest, environmental impacts and enroute losses. The facility could provide a continuous source of salmon for biological sampling to assess species and stock composition, fish health, size, age and sex composition.
The primary objectives for the project were to: 1) implement a full-scale live capture and tagging facility at Mission and in the Fraser canyon for each salmon species; 2) tag a representative sample of all salmon species, steelhead and sturgeon caught in these fishwheels, and collect DNA samples for sockeye, Chinook and steelhead; 3) use the mark-recapture data from fisheries and fishwheel samples to compute in-season escapement estimates for each of the target species; 4) provide biosampling data needed for species and stock composition estimates; and 5) provide an adequate supply of sockeye for future periodic assessments of in-river survival using radio-telemetry techniques.
Summary of Findings
- Fishwheels were successfully operated from July-October 2008 at the Crescent Island site.
- Tags were applied to most of the adult salmon, steelhead and sturgeon caught by the fishwheels. Detailed analysis of the sockeye size data from fishwheels and in-river gillnet test fisheries revealed that fishwheels on the lower Fraser River tend to catch slightly smaller sockeye than the other test fisheries.
- Fishwheel catch rates were too low and the mark-rate data from fishery sampling programs were neither sufficient nor timely enough to compute in-season estimates of abundance for the target species.
- Fishwheel provide an excellent source of fish for sampling size, age (scales), species and stock composition (DNA) for that portion of each species that migrates close to the shoreline.
- The methods used at Qualark provided reliable information on the numbers of radio-tags and total sockeye passing the Qualark site. Radio-telemetry combined with the Qualark hydroacoustic enumeration approach is a viable method for in-season evaluation of Mission sockeye abundance estimates.
- Substantial differences were observed in species composition between the off-shore Whonnock gillnet test fishery and the near-shore fishwheel sites. It is important that both areas be reliably sampled to provide an accurate estimate of the daily species composition for the daily Mission hydroacoustic counts. Mission hydroacoustic counts should be separated between the near-shore and off-shore strata and Whonnock test fishery data be used to estimate the species composition of the off-shore counts and fishwheel data be used to estimate the species composition of the near-shore counts.