Time filter

Source Type

Nanaimo, Canada

Friedland K.D.,National Oceanic and Atmospheric Administration | Ward B.R.,University of British Columbia | Welch D.W.,Kintama Research Services | Hayes S.A.,National Oceanic and Atmospheric Administration
Marine and Coastal Fisheries

Abstract: The population of anadromous steelhead Oncorhynchus mykiss in the Keogh River has been studied intensively, in part because of its pattern of declining recruitment, which is largely attributed to poor marine survival. Climate variability has changed the productivity of salmonid species in all regions of the North Pacific, with areas alternately shifting between periods of enhanced and depressed productivity. The mechanisms governing marine survival and adult recruitment are central to contemporary resource management concerns but are also of concern with regard to the long-term prospects of managing biodiversity. We provide evidence that postsmolt growth contributes to the pattern of marine survival of Keogh River steelhead over the period corresponding to smolt years 1977–1999. Size at ocean entry did not appear to have sufficient contrast to significantly affect survival. However, assessment of scale growth suggested that the fish's initial growth at sea is not as important as the sustained growth conditions during summer and fall of the postsmolt year. The return rate of steelhead was negatively correlated with sea surface temperature in the ocean domains that were assumed to provide postsmolt nursery habitat, suggesting that growth is directly affected by warming conditions or that ocean warming affects the food web upon which steelhead depend. Steelhead appear to respond to changing climate and growth regimes in a manner similar to that of their North Atlantic analog, the Atlantic Salmon Salmo salar. Comparative data show that eastern basin Atlantic Salmon populations are negatively affected by a thermal regime of increasing temperature during the postsmolt year, suggesting a relationship between postsmolt growth and survival. © 2014, © American Fisheries Society 2014. Source

Morrison P.R.,Vancouver Island University | Morrison P.R.,University of British Columbia | Groot E.P.,Vancouver Island University | Welch D.W.,Kintama Research Services
Transactions of the American Fisheries Society

To assess the potential impact of "tag effect" on seaward-migrating Coho Salmon Oncorhynchus kisutch, presmolt juveniles were surgically implanted with acoustic transmitters followed by exposure to freshwater (FW, 0‰ salinity) or seawater (SW; 30‰ salinity) for 24 h and then subjected to repeated critical swimming speed (Ucrit) trials. Three different experimental tag-treatment groups were established: control (no surgery), sham (surgery but no tag), and tagged (surgically implanted tag), with a range of 9-12 fish in each group. Tagged fish were implanted with Vemco V6 dummy acoustic transmitters (DAT: 17.0 mm long × 6 mm diameter, 1.0 g in air). After completion of two Ucrit trials, separated by a recovery period, all fish were euthanized and sampled to determine hematocrit (Hct) and plasma osmolality. In the FW exposure, the mean Ucrit of the control treatment was significantly higher than that of the tagged treatment (P = 0.04). No significant differences in swimming performance were observed among the SW treatment groups, and no significant differences were observed between Ucrit trials (Ucrit1 and Ucrit2) for any of the experimental treatments groups. Seawater exposure did, however, result in slightly reduced, but not statistically different, swimming speeds and concomitantly higher plasma osmolalities (P < 0.001) compared with FW exposure. Predictions made with data from this study suggest that sample sizes (per tag treatment) of n = 25 are sufficient to detect a 15-20% difference in Ucrit sample means with 80% power. Collectively, these data do not provide substantial statistical evidence that the swimming performance of juvenile Coho Salmon tagged with surgically implanted acoustic transmitters is significantly reduced compared with untagged fish. © American Fisheries Society 2013. Source

Melnychuk M.C.,University of British Columbia | Melnychuk M.C.,University of Washington | Walters C.J.,University of British Columbia | Christensen V.,University of British Columbia | And 2 more authors.
Marine Ecology Progress Series

Marine survival rates of many juvenile salmon populations have declined in recent decades. Although several potential causes have been proposed, there has been little conclusive evidence for which factors are responsible or not responsible for these declines. We experimentally addressed the hypothesis that exposure of coho salmon Oncorhynchus kisutch or sockeye salmon O. nerka to solar ultraviolet-B radiation (UVB) during freshwater rearing of fry and parr life-history stages increases mortality at the time of smoltification and ocean entry. Juvenile coho and sockeye salmon were reared in outdoor hatchery tanks either exposed to full spectrum sunlight or shielded from UVB radiation by plastic screens for up to 9 mo prior to release. Smolts were tagged with acoustic transmitters and detected with hydrophone receivers during their downriver and early ocean migration. Survival of treatment groups was compared using Cormack-Jolly-Seber and Burnham mark-recapture models. While exposure to UVB resulted in decreased growth of juvenile coho salmon, survivorship during the early marine period was unaffected by the UVB treatment for both populations. This first attempt to experimentally address the hypothesis of impaired survival resulting from solar UVB radiation has shown that other factors are more likely responsible for observed declines in salmon marine survival rates. © Inter-Research 2012 and Crown in the Right of Canada. Source

Wilson S.M.,Carleton University | Hinch S.G.,University of British Columbia | Drenner S.M.,University of British Columbia | Martins E.G.,Carleton University | And 4 more authors.
Marine Ecology Progress Series

Although behaviour and physiology of the reproductive migration of Pacific salmon Oncorhynchus spp. have been studied for the upriver migration, equivalent information for the coastal marine migratory phase has been difficult to obtain. Acoustic acceleration transmitters equipped with pressure sensors provide a tool to study swimming activity and migration depth of salmon in both marine and fresh water. Ocean migrating sockeye salmon O. nerka bound for the Fraser River, British Columbia (Canada), were intercepted approximately 200 km from the river entrance, tagged and tracked as they crossed several acoustic receiver lines in coastal waters and the lower Fraser River. Acceleration data were converted to swim speed using an existing statistical model. Data from 55 tagged fish revealed that swim speed and depth varied among migratory locales. Migration difficulty (freshwater migration distance and elevation to natal stream) was related to swim speed in the marine environment. Some of the variability in swim speed and depth was explained by diel and tidal cycles. In the marine environment, average (±SEM) swim speed estimate was ∼1.23 body lengths (BL) s1 at an average depth of 13 ± 0.058 m (range = 0171 m), whereas the average swim speed in the river was significantly higher at ∼1.57 BL s1 at an average (±SEM) depth of ∼9 ± 0.018 m (range = 021 m). Consistent with the physiological literature, coastal migrating fish were swimming near metabolically optimal speeds (0.91.2 BL s1). Overall this study demonstrates that using acoustic accelerometer transmitters can provide valuable insights into behaviour of homing sockeye salmon in both marine and freshwater environments. © Inter-Research and Fisheries and Oceans Canada 2014. Source

Brosnan I.G.,Cornell University | Welch D.W.,Kintama Research Services | Rechisky E.L.,Kintama Research Services | Porter A.D.,Kintama Research Services
Marine Ecology Progress Series

The impact of oceanographic processes on early marine survival of Pacific salmon is typically estimated upon adult return, 1 to 5 yr after ocean entry, and many 1000s of kilometers after initial exposure. Here, we use direct estimates of early marine survival obtained from acoustic-tagged yearling Chinook salmon Oncorhynchus tshawytscha that entered the Columbia River plume (USA) after migrating down the river and then north to the coastal waters off Willapa Bay, Washington. Plume residence time averaged 7 d, and was of such short duration that predation, rather than feeding and growth conditions, was the likely primary cause of mortality. Plume survival ranged from 0.13 to 0.86, but was stable when scaled by plume residence time, and we find that a simple exponential decay model adequately describes plume survival. Plume survival, and perhaps adult returns, could be improved by reducing plume residence time if the drivers controlling residence time were amenable to management control. However, we show that a statistical model of plume residence time that includes only sea-surface temperature far outperforms models that include river discharge and coastal upwelling. Timing hatchery releases using marine environmental forecasts could potentially improve smolt survival by minimizing their residence time in regions of poor survival. Acoustic telemetry may be used to evaluate the value and effectiveness of such approaches. © Inter-Research 2014. Source

Discover hidden collaborations