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Hinch S.G.,University of British Columbia | Cooke S.J.,Carleton University | Farrell A.P.,University of British Columbia | Miller K.M.,Canadian Department of Fisheries and Oceans | And 2 more authors.
Journal of Fish Biology | Year: 2012

Adult sockeye salmon Oncorhynchus nerka destined for the Fraser River, British Columbia are some of the most economically important populations but changes in the timing of their homeward migration have led to management challenges and conservation concerns. After a directed migration from the open ocean to the coast, this group historically would mill just off shore for 3-6 weeks prior to migrating up the Fraser River. This milling behaviour changed abruptly in 1995 and thereafter, decreasing to only a few days in some years (termed early migration), with dramatic consequences that have necessitated risk-averse management strategies. Early migrating fish consistently suffer extremely high mortality (exceeding 90% in some years) during freshwater migration and on spawning grounds prior to spawning. This synthesis examines multidisciplinary, collaborative research aimed at understanding what triggers early migration, why it results in high mortality, and how fisheries managers can utilize these scientific results. Tissue analyses from thousands of O. nerka captured along their migration trajectory from ocean to spawning grounds, including hundreds that were tracked with biotelemetry, have revealed that early migrants are more reproductively advanced and ill-prepared for osmoregulatory transition upon their entry into fresh water. Gene array profiles indicate that many early migrants are also immunocompromised and stressed, carrying a genomic profile consistent with a viral infection. The causes of these physiological changes are still under investigation. Early migration brings O. nerka into the river when it is 3-6° C warmer than historical norms, which for some late-run populations approaches or exceeds their critical maxima leading to the collapse of metabolic and cardiac scope, and mortality. As peak spawning dates have not changed, the surviving early migrants tend to mill in warm lakes near to spawning areas. These results in the accumulation of many more thermal units and longer exposures to freshwater diseases and parasites compared to fish that delay freshwater entry by milling in the cool ocean environment. Experiments have confirmed that thermally driven processes are a primary cause of mortality for early-entry migrants. The Fraser River late-run O. nerka early migration phenomenon illustrates the complex links that exist between salmonid physiology, behaviour and environment and the pivotal role that water temperature can have on population-specific. © 2012 The Authors. Journal of Fish Biology © 2012 The Fisheries Society of the British Isles.

Martins E.G.,University of British Columbia | Hinch S.G.,University of British Columbia | Patterson D.A.,Simon Fraser University | Hague M.J.,Simon Fraser University | And 5 more authors.
Global Change Biology | Year: 2011

Mean summer water temperatures in the Fraser River (British Columbia, Canada) have increased by ~1.5 °C since the 1950s. In recent years, record high river temperatures during spawning migrations of Fraser River sockeye salmon (Oncorhynchus nerka) have been associated with high mortality events, raising concerns about long-term viability of the numerous natal stocks faced with climate warming. In this study, the effect of freshwater thermal experience on spawning migration survival was estimated by fitting capture-recapture models to telemetry data collected for 1474 adults (captured in either the ocean or river between 2002 and 2007) from four Fraser River sockeye salmon stock-aggregates (Chilko, Quesnel, Stellako-Late Stuart and Adams). Survival of Adams sockeye salmon was the most impacted by warm temperatures encountered in the lower river, followed by that of Stellako-Late Stuart and Quesnel. In contrast, survival of Chilko fish was insensitive to the encountered river temperature. In all stocks, in-river survival of ocean-captured sockeye salmon was higher than that of river-captured fish and, generally, the difference was more pronounced under warm temperatures. The survival-temperature relationships for ocean-captured fish were used to predict historic (1961-1990) and future (2010-2099) survival under simulated lower river thermal experiences for the Quesnel, Stellako-Late Stuart and Adams stocks. A decrease of 9-16% in survival of all these stocks was predicted by the end of the century if the Fraser River continues to warm as expected. However, the decrease in future survival of Adams sockeye salmon would occur only if fish continue to enter the river abnormally early, towards warmer periods of the summer, as they have done since 1995. The survival estimates and predictions presented here are likely optimistic and emphasize the need to consider stock-specific responses to temperature and climate warming into fisheries management and conservation strategies. © 2010 Blackwell Publishing Ltd.

Andres Araujo H.,Canadian Department of Fisheries and Oceans | Holt C.,Canadian Department of Fisheries and Oceans | Curtis J.M.R.,Canadian Department of Fisheries and Oceans | Perry R.I.,Canadian Department of Fisheries and Oceans | And 2 more authors.
Progress in Oceanography | Year: 2013

We evaluated the effects of biophysical conditions and hatchery production on the early marine survival of coho salmon Oncorhynchus kisutch in the Strait of Georgia, British Columbia, Canada. Due to a paucity of balanced multivariate ecosystem data, we developed a probabilistic network that integrated physical and ecological data and information from literature, expert opinion, oceanographic models, and in situ observations. This approach allowed us to evaluate alternate hypotheses about drivers of early marine survival while accounting for uncertainties in relationships among variables. Probabilistic networks allow users to explore multiple environmental settings and evaluate the consequences of management decisions under current and projected future states. We found that the zooplankton biomass anomaly, calanoid copepod biomass, and herring biomass were the best indicators of early marine survival. It also appears that concentrating hatchery supplementation during periods of negative PDO and ENSO (Pacific Decadal and El Niño Southern Oscillation respectively), indicative of generally favorable ocean conditions for salmon, tends to increase survival of hatchery coho salmon while minimizing negative impacts on the survival of wild juveniles. Scientists and managers can benefit from the approach presented here by exploring multiple scenarios, providing a basis for open and repeatable ecosystem-based risk assessments when data are limited. © 2013 Elsevier Ltd.

Beacham T.D.,Canadian Department of Fisheries and Oceans | Mcintosh B.,Canadian Department of Fisheries and Oceans | MacConnachie C.,Canadian Department of Fisheries and Oceans | Spilsted B.,Canadian Department of Fisheries and Oceans | White B.A.,Pacific Salmon Commission
Fishery Bulletin | Year: 2012

Population structure of pink salmon (Oncorhynchus gorbuscha) from British Columbia and Washington was examined with a survey of microsatellite variation to describe the distribution of genetic variation. Variation at 16 microsatellite loci was surveyed for approximately 46,500 pink salmon sampled from 146 locations in the odd-year broodline and from 116 locations in the even-year broodline. An index of genetic differentiation, F ST, over all populations and loci in the odd-year broodline was 0.005, with individual locus values ranging from 0.002 to 0.025. Population differentiation was less in the even-year broodline, with a F ST value of 0.002 over all loci, and with individual locus values ranging from 0.001 to 0.005. Greater genetic diversity was observed in the odd-year broodline. Differentiation in pink salmon allele frequencies between broodlines was approximately 5.5 times greater than regional differentiation within broodlines. A regional structuring of populations was the general pattern observed, and a greater regional structure in the odd-year broodline than in the even-year broodline. The geographic distribution of microsatellite variation in populations of pink salmon likely reflects a distribution of broodlines from separate refuges after the last glaciation period.

Putman N.F.,Oregon State University | Putman N.F.,National Oceanic and Atmospheric Administration | Jenkins E.S.,Pacific Salmon Commission | Michielsens C.G.J.,Pacific Salmon Commission | And 2 more authors.
Journal of the Royal Society Interface | Year: 2014

Animals navigate using a variety of sensory cues, but how each is weighted during different phases of movement (e.g. dispersal, foraging, homing) is controversial. Here, we examine the geomagnetic and olfactory imprinting hypotheses of natal homing with datasets that recorded variation in the migratory routes of sockeye (Oncorhynchus nerka) and pink (Oncorhynchus gorbuscha) salmon returning from the Pacific Ocean to the Fraser River, British Columbia. Drift of the magnetic field (i.e. geomagnetic imprinting) uniquely accounted for 23.2% and 44.0% of the variation in migration routes for sockeye and pink salmon, respectively. Ocean circulation (i.e. olfactory imprinting) predicted 6.1% and 0.1% of the variation in sockeye and pink migration routes, respectively. Sea surface temperature (a variable influencing salmon distribution but not navigation, directly) accounted for 13.0% of the variation in sockeye migration but was unrelated to pink migration. These findings suggest that geomagnetic navigation plays an important role in long-distance homing in salmon and that consideration of navigation mechanisms can aid in the management of migratory fishes by better predicting movement patterns. Finally, given the diversity of animals that use the Earth's magnetic field for navigation, geomagnetic drift may provide a unifying explanation for spatio-temporal variation in the movement patterns of many species. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Macdonald J.S.,Pacific Research Fisheries Center | Patterson D.A.,Simon Fraser University | Hague M.J.,Simon Fraser University | Guthrie I.C.,Pacific Salmon Commission
Transactions of the American Fisheries Society | Year: 2010

The impact of freshwater environmental factors on spawning migration mortality was modeled to provide a predictive tool for fisheries management of four run timing groups of Fraser River sockeye salmon Oncorhynchus nerka: early Stuart (Stuart Lake), early summer, summer, and late. We tested the significance of different measures of water temperature, discharge, fish abundance, and entry timing for forecasting discrepancies between lower-river and upriver escapement estimates using multiple regressions of principal component scores. Descriptive discrepancy models (i.e., "management adjustment" models) identified using Akaike's information criterion were consistent with the known biology of each group. For example, temperature and discharge thresholds were selected for early Stuart run discrepancy models, reflecting the extremes in both variables experienced by these early migrants. Predictive discrepancy models were also generated for each run timing group by using the limited number of environmental variables that are available in-season to fisheries managers. Even predictive discrepancy models using simple environmental metrics of average river temperature, flow, and river entry timing provide a valuable tool for forecasting relative indices of spawning migration mortality. This study provides an example of how environmentally based predictive tools can be used to inform fisheries management decisions and improve the probability of achieving spawning escapement targets. © American Fisheries Society 2010.

Hague M.J.,Simon Fraser University | Hague M.J.,Pacific Salmon Commission | Patterson D.A.,Simon Fraser University
North American Journal of Fisheries Management | Year: 2014

Warming rivers and an improved knowledge of thermal impacts on fish are fueling a need for simple tools to generate water temperature forecasts that aid in decision making for the management of aquatic resources. Although there is strong evidence for temperature-dependent mortality in freshwater fish populations, the application of water temperature models for in-season fisheries management is still limited due to a lack of appropriate temperature thresholds and due to uncertainty in forecasts. We evaluated the ability of statistical models based on seasonal trends, air temperature, and discharge to produce daily forecasts of water temperature in the Fraser River, British Columbia, including explicit quantification of uncertainty in predictor variables. For all models evaluated (with and without air temperature and/or discharge predictor variables), the top model choice varied as a function of environmental conditions, uncertainty in the air temperature forecasts used to predict water temperature, and the selection of quantitative performance criteria (i.e., defining the "best" model based on the smallest mean raw error or based on the ability to accurately forecast extreme water temperatures). Water temperature forecasts averaged across 10 d produced by simple models that were fitted only to historical seasonal water temperature trends were as accurate as forecasts generated from uncertain air temperature predictions. Models fitted to air temperature were critical for forecasting high temperature thresholds; even the use of uncertain air temperature forecasts predicted high water temperatures with greater accuracy than models that lacked an air temperature covariate. In contrast, models that were fitted to discharge variables lowered the rate of false-negative and false-positive errors associated with estimating below-average temperatures. On the basis of our findings, we suggest that fisheries managers should quantify the effect of uncertainties in model predictor variables when assessing water temperature models and should evaluate model performance in the context of system-specific conditions and management objectives. Received May 15, 2013; accepted September 13, 2013. © 2014 Copyright Taylor and Francis Group, LLC.

Mckinnell S.,C o Institute of Ocean science | Reichardt M.,Pacific Salmon Commission
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2012

Mortality of salmon in the ocean is considered to be greatest during the first few months and that its magnitude is an inverse of growth. First year marine growth (M1) in two Fraser River sockeye salmon (Oncorhynchus nerka) populations was positively correlated, reflecting a shared oceanic experience as postsmolts. M1 declined abruptly in both populations after 1977, corresponding to a well-documented change in climate. The reduction in average M1 was not accompanied by a detectable reduction in average survival. In both populations, M1 was significantly greater in even years when juvenile pink salmon (Oncorhynchus gorbuscha) are abundant in the Strait of Georgia, suggesting that interspecific competition there has little effect on M1. All correlations of M1 with regional pink salmon or sockeye salmon abundances, lagged to align ocean entry years, were negative, but few (pink) or none (sockeye) were statistically significant. The negative correlations were due to the long-term changes (pink salmon abundance increasing, sockeye M1 smaller). Odd year dominance of juvenile pink salmon in northern British Columbia, Canada, is persistent and corresponds with the biennial pattern of M1 variation in Fraser River sockeye salmon and may be the source of the significant odd-even year line effect on M1.

Xie Y.,Pacific Salmon Commission | Martens F.J.,Pacific Salmon Commission
North American Journal of Fisheries Management | Year: 2014

Systematic hourly sampling is a logistically favorable method for hydroacoustic estimation of fish passage through constricted passageways or finite sections of a river monitored by fixed-location sonar systems. Similar to simple random and hourly stratified random sampling, systematic hourly sampling produces unbiased estimates of fish passage. Variances of estimates produced by systematic hourly sampling are determined by the sampling fraction, f, variance of the underlying process, S2, and correlations among all hourly strata of the process. This intrahour correlation dependency makes it difficult to accurately evaluate the precision of the estimate when the complete temporal pattern of the process is unavailable. Fish passage is rarely counted continuously, so the uncertainty of estimated mean by systematically subsampled fish counts is traditionally estimated using variance estimators. Variance estimates by these estimators are likely biased and subject to potentially large errors. We present an alternative approach for estimating the precision of systematic hourly sampling using an empirical relation between precision and sampling fraction established from continuous fish counts acquired by imaging sonar for a wide range of migration scenarios of Pacific salmon Oncorhynchus spp. in the lower Fraser River. The empirical relation indicates that a CV (100·SD/mean) of 5.5% can be achieved by the systematic hourly counting of fish passage at a counting effort of 10 min/h, while increasing the counting effort to 20 min/h only leads to a marginally improved CV of 4.1%. The data-based analysis also shows that the precision of systematic sampling can be gained more efficiently and consistently by increasing the sampling rate than by lengthening the sampling time.Received June 6, 2013; accepted January 21, 2014. © 2014 © American Fisheries Society 2014.

Xie Y.,Pacific Salmon Commission | Michielsens C.G.J.,Pacific Salmon Commission | Martens F.J.,Pacific Salmon Commission
ICES Journal of Marine Science | Year: 2012

Hydroacoustic data acquired for estimating fish populations contain information on both fish and non-fish targets, so sonar technicians traditionally rely on their knowledge of fish behaviour and experience with hydroacoustics to remove non-fish targets from the hydroacoustic data. This process is often labour-intensive and time-consuming, making real-time assessment of fish populations difficult. Simple solutions are not always available for all circumstances. However, the split-beam sonar data collected in the lower Fraser River, British Columbia, Canada, showed distinct signatures between actively swimming fish and non-fish objects such as drifting debris, surface bubbles, and stationary objects in the water column and off the river bottom. Acoustic tracks of fish and non-fish targets were characterized by differentiable statistical patterns that were amenable to discriminant function analysis (DFA). An application of DFA to segregate fish and non-fish targets detected by a split-beam sonar system in the lower Fraser River is presented, characteristics of user-identified fish and non-fish acoustic tracks being utilized as learning samples for the DFA. Also, a method to rank the discriminating power of individual variables is presented, providing guidance for constructing efficient and effective discriminant functions with variables that offer high discriminating power. The DFA yielded classification accuracies of 96 for fish and 91 for non-fish tracks and reduced the manual sorting time by 5075. © 2012 International Council for the Exploration of the Sea.

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