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Furey N.B.,University of British Columbia | Vincent S.P.,Seymour Salmonid Society | Hinch S.G.,University of British Columbia | Welch D.W.,Kintama Research Services Ltd
PLoS ONE | Year: 2015

Variability in animal migratory behavior is expected to influence fitness, but few empirical examples demonstrating this relationship exist. The initial marine phase in the migration of juvenile salmon smolts has been identified as a potentially critical life history stage to overall population productivity, yet how fine-scale migration routes may influence survival are unknown. Large-scale acoustic telemetry studies have estimated survival rates of outmigrant Pacific salmon smolts through the Strait of Georgia (SOG) along the British Columbian coastline to the Pacific Ocean, but these data have not been used to identify and characterize fine-scale movements. Data collected on over 850 sockeye salmon (Oncorhynchus nerka) and steelhead (Oncorhynchus mykiss) smolts detected at an array in the Strait of Georgia in 2004-2008 and 2010-2013 were analyzed to characterize migration routes and link movements to subsequent survival at an array 250 km further along the marine migration pathway. Both species exhibited disproportionate use of the most eastern route in the Strait of Georgia (Malaspina Strait). While many smolts moved across the northern Strait of Georgia acoustic array with no indication of long-term milling or large-scale east-to-west movements, large proportions (20-40% of sockeye and 30-50% of steelhead) exhibited a different behavior, apparently moving in a westward or counterclockwise pattern. Variability in migratory behavior for both species was linked to subsequent survival through the Strait of Georgia. Survival for both species was influenced by initial east-to-west location, and sockeye were further influenced by migration timing and duration of time spent near the northern Strait of Georgia array. Westward movements result in a net transport of smolts from Malaspina Strait to the Strait of Georgia, particularly for steelhead. Counterclockwise movements may be due to the currents in this area during the time of outmigration, and the higher proportion of steelhead smolts exhibiting this counterclockwise behavior may reflect a greater exposure to wind-altered currents for the more surface-oriented steelhead. Our results provide an empirical example of how movements can affect migration survival, for which examples remain rare in movement ecology, confirming that variability in movements themselves are an important part of the migratory process. Copyright: © 2015 Furey et al. Source

Melnychuk M.C.,University of British Columbia | Korman J.,Ecometric Research | Hausch S.,University of Calgary | Welch D.W.,Kintama Research Services Ltd | And 2 more authors.
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2014

We observed large survival differences between wild and hatchery-reared steelhead trout (Oncorhynchus mykiss) during the juvenile downstream migration immediately after release, which persisted through adult life. Following a railway spill of sodium hydroxide into the Cheakamus River, British Columbia, a short-term conservation hatchery rearing program was implemented for steelhead. We used acoustic telemetry and mark-recapture models to estimate survival of wild and (or) hatchery-reared steelhead during 4 years of the smolt migration, with both groups released in 2008. After adjusting for estimated freshwater residualization, 7%-13% of wild smolts and 30%-40% of hatchery smolts died in the first 3 km of the migration. Estimated survival from release to ocean entry was 71%-84% for wild fish and 26%-40% for hatchery fish and to exit from the Strait of Georgia system was 22%-33% for wild fish and 3.5%-6.7% for hatchery fish. A calculated 2.3-fold survival difference established during the downstream migration was similar to that after the return of adult spawners, as return rates were 8.0% for wild fish and 4.1% for hatchery fish. Contrary to current understanding, a large proportion of salmon mortality in the smolt-to-adult period, commonly termed "marine mortality", may actually occur prior to ocean entry. Source

Balfry S.,University of British Columbia | Balfry S.,Center for Aquaculture and Environmental Research | Welch D.W.,Kintama Research Services Ltd | Atkinson J.,University of British Columbia | And 2 more authors.
PLoS ONE | Year: 2011

Early marine migratory behaviour and apparent survival of hatchery-reared Seymour River steelhead (Oncorhynchus mykiss) smolts was examined over a four year period (2006-2009) to assess the impact of various management strategies on improving early marine survival. Acoustically tagged smolts were released to measure their survival using estuary and coastal marine receivers forming components of the Pacific Ocean Shelf Tracking (POST) array. Early marine survival was statistically indistinguishable between releases of summer run and winter run steelhead races, night and day releases, and groups released 10 days apart. In 2009, the survival of summer run steelhead released into the river was again trialed against groups released directly into the ocean at a distance from the river mouth. Apparent survival was improved significantly for the ocean released groups. The health and physiological status of the various release groups were monitored in years 2007-2009, and results indicate that the fish were in good health, with no clinical signs of disease at the time of release. The possibility of a disease event contributing to early marine mortality was further examined in 2009 by vaccinating half of the released fish against common fish diseases (vibriosis, furunculosis). The results suggest that marine survival may be enhanced using this approach, although not to the extent observed when the smolts were transported away from the river mouth before release. In summary, direct experimental testing of different release strategies using the POST array to measure ocean survival accelerated the scientific process by allowing rapid collection of data which enabled the rejection of several existing theories and allowed tentative identification of several new alternative approaches that might improve early marine survival of Seymour River steelhead. © 2011 Balfry et al. Source

Collins A.L.,University of British Columbia | Hinch S.G.,University of British Columbia | Welch D.W.,Kintama Research Services Ltd | Cooke S.J.,Carleton University | Clark T.D.,Australian Institute of Marine Science
Transactions of the American Fisheries Society | Year: 2013

Juvenile hatchery-reared Sockeye Salmon Oncorhynchus nerka from Cultus Lake, British Columbia, were implanted during their smolt phase with one of three sizes of dummy acoustic tags to assess how tag burden (tag mass: body mass ratios ranging from 1.3% to 13.6% in air) influenced prolonged swimming performance, survival, and postsurgical wound healing in freshwater for up to 16.5 d and following a transition to seawater for 9 d. Tagged fish were compared with surgical shams and control fish (no tag, no surgery). Fish subjected to sham surgery treatments had mean swim times similar to those of control fish; however, tagged fish had a significantly lower probability of swimming the mean time of nontagged control fish. In addition, we found that the effect of tagging on swimming performance was exacerbated by tag burden and that higher tag burdens decreased the swimming performance of tagged individuals. Fish with tag burdens ≥8% had shorter swimming durations than fish with tag burdens <8%. The incisions of fish implanted with smaller tags healed more quickly than those of fish implanted with the largest tag. Overall, survival was high (≥95%) and in freshwater mortalities only occurred in fish that had tag burdens greater than 6%. These findings have important implications for studies using tagging technologies to examine the behavior and survival of migrating salmon smolts.Received October 13, 2011; accepted October 22, 2012. © 2013 Copyright Taylor and Francis Group, LLC. Source

Tucker S.,Canadian Department of Fisheries and Oceans | Trudel M.,Canadian Department of Fisheries and Oceans | Trudel M.,University of Victoria | Welch D.W.,Canadian Department of Fisheries and Oceans | And 6 more authors.
Marine Ecology Progress Series | Year: 2012

While recent studies have evaluated the stock-specific coastal migration of juvenile Chinook salmon, it remains unclear if these seasonal patterns are consistent between years, particularly when ocean conditions change dramatically. Here we contrast the abundance, distribution and seasonal stock compositions of juvenile Chinook salmon between years in 3 oceanographic regions of the Pacific from southern British Columbia to southeast Alaska. Between 1998 and 2008, we surveyed salmon in various months from June through March, in different regions along the shelf. Variable conditions in the North Pacific Ocean, as well as large overall shifts in ocean regimes were extensively documented over this decade. We employed genetic stock identification to identify mixed-stock compositions; fish (n = 6274) were allocated to one of 15 regional and 40 subregional stocks. Catch-per-unit-effort and distribution of salmon, as denoted by centre of mass, varied significantly between seasons, regions and years. In a similar manner, fish body size and dryweight varied significantly between years, seasons and regions. Despite these inter-annual differences in catch, distribution, fish growth performance and large variations in ocean conditions encountered by salmon over the time period of the study, we observed no response in terms of shifts in stock-specific distributions. Regional stock composition was similar between years, suggesting migration patterns for all stocks remain consistent despite fluctuations in the marine environment: local stocks remain resident in respective coastal areas during their first year at sea, except for Columbia River salmon, which move quickly into waters north of Vancouver Island in summer. © 2012 Fisheries and Oceans Canada. Source

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