In recent years, large numbers of late-run Fraser River sockeye salmon Oncorhynchus nerka have died in freshwater areas before they spawned. We used radiotelemetry techniques to determine river entry timing, migration rates, and survival for the summer and late runs of sockeye salmon in 2002 and 2003. Fishery removals and river detections accounted for 62% of the 873 fish tagged and released in marine areas in 2002. Some late-run fish migrated from release sites to the Mission hydroacoustic site in 8-10 d and migrated upstream with the summer run. Most late-run fish remained in the Strait of Georgia for 15-33 d and entered the river after the summer run. Tracking data indicated that individual sockeye salmon maintained essentially the same chronological order as they migrated up the Fraser and Thompson rivers. Summer-run stocks traveled faster between Mission and the Thompson Junction (33-39 km/d) than late-run fish (17-21 km/d). After accounting for fishery removals, the river survival rate for summer-run fish was 92%, and differences between the three release timing groups were not significant. In contrast, the first migration group of late-run fish that passed Mission had significantly lower survival (13%) than all other timing groups. The survival rate for the second and third river entry groups combined (74%) was significantly lower than that of the fourth group (92%). Period-specific survival rates were used to define a relationship between river entry timing and survival and to identify additional factors influencing river entry timing for late-run fish. These relationships may be useful in predicting river survival rates for late-run stocks in future years.

The migration of 1,263 adult radio-tagged steelhead Oncorhynchus mykiss was assessed in the Nass, Skeena, Bella Coola, Fraser, and mid-Columbia rivers from 1993 to 2001. Of the summer-run steelhead tagged in the mid-Columbia River, 80-87% eventually continued their upstream migration after being tagged, and 87-90% of those were detected in spawning areas. Similar results were seen for summer-run steelhead tracked on the Nass and Skeena rivers. Mid-Columbia summer-run steelhead stocks that passed five dams en route to their spawning destinations (Methow and Okanogan rivers) traveled at a median rate of 20 km/d, which exceeded the median rates for summer-run steelhead tracked on the Nass (3.8 km/d) and Skeena rivers (12-16 km/d). The upstream migration rates were best explained by river gradient and distance of the study area from the ocean. When the effects of river gradient and reach location were taken into account, impoundment was still a significant factor increasing the upstream migration speeds of summer-run steelhead. Kelting speeds varied widely among rivers and did not appear to be a function of gradient.[Article] tion rates is important to make informed decisions about in-river fisheries, especially in rivers shared by both targeted and protected stocks.Another goal of this paper was to compare migration and kelting rates between mid-Columbia River steelhead (which must navigate past as many as five dams between their release site and their spawning ground) and steelhead in naturally flowing BC rivers. Using radiotelemetry-derived estimates of migration and kelting rates (i.e., the directed downstream movements of steelhead after spawning), we explored whether the challenges presented in an impounded river system are more severe than those in more naturally flowing rivers. Decisions to build or breach dams should be made with an understanding of the effects of impoundment on the ecology of steelhead populations. FIGURE 1.-Map showing the watersheds of the five study areas (shaded areas in the lower left panel) and the locations of the fixed-station receivers (triangles) used in the Nass and Skeena (upper left panel), Fraser (upper right panel), and mid-Columbia River (lower right panel) studies. Monitoring arrays at the five mid-Columbia dams are marked with squares. 740 ENGLISH ET AL. 742 ENGLISH ET AL. 744 ENGLISH ET AL.