Salish Sea Marine Survival Project

58 Marine Release at West Van (n=160) and River Release at Seymour River (n=83). SUMMARY OF RESULTS TO DATE 1. Evaluate the migration and survival rates of juvenile salmon in the Strait of Georgia, the Discovery Islands and Johnstone Strait (Sock- eye and steelhead) 2015-2017. Seymour steelhead 2015: In 2015 age-1 hatchery steelhead smolts were tagged at the Seymour River Hatch- ery in North Vancouver and released at two locations to test route- and location-specific survival across outmigra- tion (Figure 2). Survival to the Queen Charlotte Strait array was higher for fish released at West Vancouver (27.3%) than fish released in the lower Seymour (9.1%) (Figure 3). Thus, transporting fish ~18 km resulted in a 3-fold increase in survival. Seymour River and Burrard Inlet were noted as regions of particularly low survival for migrating smolts. We are not sure why, but these areas may be predation hotspots. Travel rates were about 2-3 times faster through the same marine regions as they found with Sockeye smolts — see below (e.g., 15-20 km per day in the Strait of Georgia, 40-50 km per day in the Discovery Islands, 30-40 km per day at northern Vancouver Island). Their faster speeds are probably due to their much larger body sizes compared to Sockeye smolts. Chilko Sockeye 2010-2014: Age-2 Chilko Sockeye have been tagged with V7 tags, released at the outlet of Chilko Lake and tracked as they cross a number of arrays (Figure 4). Survival patterns were as follows (Figure 5): Release to 14 km (B): 63 – 90% survival Release to Fraser River Mouth (G): 21-48% survival Release to Queen Charlotte Strait (K): 3-10% survival Chilko Sockeye 2016: In 2016, with the availability of the small V4 tag, it was possible for the first time to tag smaller age-1 Sockeye smolts (important as these make up the majority of the Chilko Sockeye smolts) (Figure 6). Surprisingly, survival of age-1 fish was higher than that of age-2 smolts, at least in the Chilko River. However, age-1 fish had lower tag burdens, potentially influencing this result. The patterns of mortality were similar in each, with higher mortality in upper Chilko and Chilcotin Rivers (which appear to be a potential mortality hotspot), low mortality in the more turbid waters of the Fraser River and then higher mortality again when smolts enter the Strait of Georgia (Figure 7). Travel rates of smolts in the upper Chilko River was relatively slow at about 10-20 km per day though they were faster in the Chilcotin River at about 100 km per day. In the Fraser River, smolts migrated more quickly at about 180-190 km per day (in all sections there were no differences between the ages). In the marine segments smolts travelled at 10 km per day (Strait of Georgia) and 15 km per day (Discovery Islands) — only one year olds were abundant enough to assess these travel rates. Please see http://kintama.com/animator/ dep/Chilko2016_sockeye/ for an animation of the movements of tagged Chilko Sockeye during 2016. Figure 2. Release locations for Seymour steelhead study. Figure provided by Steve Healy. Figure 3. Relative survival of Seymour steelhead released in Seymour River vs West Van. Figure provided by Steve Healy. Figure 4. Release site (A) and array locations for Chilko Sockeye studies (A-K). Figure provided by Scott Hinch. Contents of a single bull trout stomach. Up to 69 sockeye smolts were found in a single trout. Photo by Nathan Furey.

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