Adult Salmon Research Articles

How riparian and floodplain restoration modify the effects of increasing temperature on adult salmon spawner abundance in the Chehalis River, WA.

Stream temperatures in the Pacific Northwest are projected to increase with climate change, placing additional stress on cold-water salmonids. We modeled the potential impact of increased stream temperatures on four anadromous salmonid populations in the Chehalis River Basin (spring-run and fall-run Chinook salmon Oncorhynchus tshawytscha, coho salmon O. kisutch, and steelhead O. mykiss), as well as the potential for floodplain reconnection and stream shade restoration to offset the effects of future temperature increases. In the Chehalis River Basin, peak summer stream temperatures are predicted to increase by as much as 3°C by late-century, but restoration actions can locally decrease temperatures by as much as 6°C. On average, however, basin-wide average stream temperatures are expected to increase because most reaches have low temperature reduction potential for either restoration action relative to climate change. Results from the life cycle models indicated that, without restoration actions, increased summer temperatures are likely to produce significant declines in spawner abundance by late-century for coho (-29%), steelhead (-34%), and spring-run Chinook salmon (-95%), and smaller decreases for fall-run Chinook salmon (-17%). Restoration actions reduced these declines in all cases, although model results suggest that temperature restoration alone may not fully mitigate effects of future temperature increases. Notably, floodplain reconnection provided a greater benefit than riparian restoration for steelhead and both Chinook salmon populations, but riparian restoration provided a greater benefit for coho. This pattern emerged because coho salmon tend to spawn and rear in smaller streams where shade restoration has a larger effect on stream temperature, whereas Chinook and steelhead tend to occupy larger rivers where temperatures are more influenced by floodplain connectivity. Spring-run Chinook salmon are the only population for which peak temperatures affect adult prespawn survival in addition to rearing survival, making them the most sensitive species to increasing stream temperatures.

An information theory-based approach to characterize drivers of upstream salmon migration

The migration timing of Pacific salmon in the Columbia River basin is subject to multiple influences related to climate, human water resource management, and lagged effects such as oceanic conditions. We apply an information theory-based approach to analyze drivers of adult Chinook salmon migration within the spring and fall spawning seasons and between years based on salmon counts at dams along the Columbia and Snake Rivers. Time-lagged mutual information and information decomposition measures, which characterize lagged and nonlinear dependencies as reductions in uncertainty, are used to detect interactions between salmon counts and lagged streamflows, air and water temperatures, precipitation, snowpack, climate indices and downstream salmon counts. At a daily timescale, these interdependencies reflect migration timing and show differences between fall and spring run salmon, while dependencies based on variables at an annual resolution reflect long-term predictability. We also highlight several types of joint dependencies where predictability of salmon counts depends on the knowledge of multiple lagged sources. This study illustrates how co-varying human and natural drivers could propagate to influence salmon migration timing or overall returns, and how nonlinear types of dependencies between variables enhance predictability of a target. This information-based framework is broadly applicable to assess driving factors in other types of complex water resources systems or species life cycles.

Live transport of Atlantic salmon in open and closed systems: Water quality, stress and recovery

The goal of the study was to compare open and closed transports of adult Atlantic salmon in terms of water quality and stress (blood chemistry and white muscle biochemistry). The study comprised of two phases: (i) live transport from a commercial farm by vessel (open system) and vehicle (closed system) to flow-through laboratory tanks and (ii) after post-transport recovery, simulated live transports in open and closed systems. The stress reaction the salmon experienced during transfer from fish farm to laboratory tanks was severe. Some delayed mortalities were observed possibly related to extreme acidosis. The fish were left to recover for 65 h before the simulated open and closed transports were carried out. By then, they had not yet fully recovered to baseline levels. The simulated transports did not cause excessive stress reactions relative to the partially recovered fish. However, deteriorating water quality during closed transport eventually affected fish behaviour where fish welfare could be questioned. The main finding was that crowding and transport due to commercial transport overshadowed stress-related results obtained during the laboratory study. The results may also be viewed as effects of repeated fish handling operations, a typical feature of salmon farming.

Optimum timing and size at release of chum salmon: Improving survival by modifying hatchery practices

AbstractAn existing conceptual model that assessed the timing of and size at release of juvenile Japanese chum salmon in Japanese waters is modified using data obtained from young salmon collected in coastal waters off Kombumori, eastern Hokkaido, Japan. The early life histories of Tokachi River late‐migrating chum salmon are estimated based on microstructural analysis of thermally marked otoliths from recaptured fish. A revised model is presented that reveals the optimal timing of and size at release of chum salmon juveniles to be dependent upon their size at sea entry and sea surface temperature (SST) near Tokachi River mouth. Juvenile salmon are assumed to grow at a fixed rate after sea entry and to reach a target fork length upon arrival in Kombumori waters when SST conditions are within a specific optimal range. However, because of annual variation in SST, the size at and timing of juvenile chum salmon sea entry following their release from hatcheries represents a moving target, which flexible hatchery release practices are required to meet. Return rates of adult chum salmon to Tokachi River correlate positively with the number of days elapsed between the period when SST is suitable near the river mouth where they enter the sea, and SST conditions in Kombumori waters, which suggests that in years when SST increases rapidly the survival of salmon tends to decline. Windows of optimal times of and sizes at release are proposed for juvenile chum salmon to improve their survival and hatchery success.

Diving and feeding of adult Atlantic salmon when migrating through the coastal zone in Norway

Atlantic salmon post-spawners from a population in northern Norway were tagged with data storage tags (N = 773), and the depth use and diving behaviour of recaptured individuals within the coastal zone were examined, both on their outward migration to sea (N = 44) and their return to the natal river after overwintering at sea (N = 34). In addition, the stomach contents of 909 returning adults caught in the fjord were examined to determine the extent to which, how recently and on what species they had fed. The tagged individuals migrated through surface waters and performed aperiodic dives, regardless of whether they were leaving the fjord as post-spawners (kelts) or returning after a winter or more at sea. However, diving behaviour differed between the fjord and outer coast. During both outward and return migration, dives when fish were likely in the fjord were shallower than on the outer coast. Deep dives of longer duration were more frequent on the outer coast than in the fjord. The stomach content analysis of salmon captured in the fjord did not show strong evidence of recent feeding: 58% of the salmon had empty stomachs, and most stomach contents were highly digested fish (mainly herring, but some capelin and unidentifiable species). We conclude that the inferred diving behaviour in the coastal zone, both on outward migration to sea and on return to the natal river, did not provide sufficient evidence of foraging within the water column, and hypothesize that diving in search for navigation cues is a more likely explanation.

Effect of food amount and temperature on growth rate and aerobic scope of juvenile chum salmon

Offshore migration of Pacific salmon Oncorhynchus spp. is partly triggered by increasing body size and high motility in the early stages of life. The survival of juvenile salmon may depend on their growth rate during the first few months in the sea, and this factor partly regulates the dynamics of adult populations. Here, we assessed the effects of water temperature and food availability on the growth of juvenile chum salmon O. keta. In addition, by combining the measurements of metabolic performance for growth and activity (Absolute Aerobic Scope: AAS) with a bioenergetics model, we estimated the energy allocation for different activities in the juveniles. Under high temperatures (14 °C), juveniles reared at low food levels (1% body weight) allocated less than half their energy for growth than those reared at high food levels (4% body weight). These findings suggest that high temperature and low food level constrain the growth of juveniles, providing an insight into the effect of the recent increase in warm and low-nutrient water masses on survival of juveniles and catches of adult chum salmon on the Pacific side of Honshu Island, Japan.

Using a mechanistic framework to model the density of an aquatic parasite Ceratonova shasta.

Ceratonova shasta is a myxozoan parasite endemic to the Pacific Northwest of North America that is linked to low survival rates of juvenile salmonids in some watersheds such as the Klamath River basin. The density of C. shasta actinospores in the water column is typically highest in the spring (March–June), and directly influences infection rates for outmigrating juvenile salmonids. Current management approaches require quantities of C. shasta density to assess disease risk and estimate survival of juvenile salmonids. Therefore, we developed a model to simulate the density of waterborne C. shasta actinospores using a mechanistic framework based on abiotic drivers and informed by empirical data. The model quantified factors that describe the key features of parasite abundance during the period of juvenile salmon outmigration, including the week of initial detection (onset), seasonal pattern of spore density, and peak density of C. shasta. Spore onset was simulated by a bio-physical degree-day model using the timing of adult salmon spawning and accumulation of thermal units for parasite development. Normalized spore density was simulated by a quadratic regression model based on a parabolic thermal response with river water temperature. Peak spore density was simulated based on retained explanatory variables in a generalized linear model that included the prevalence of infection in hatchery-origin Chinook juveniles the previous year and the occurrence of flushing flows (≥171 m3/s). The final model performed well, closely matched the initial detections (onset) of spores, and explained inter-annual variations for most water years. Our C. shasta model has direct applications as a management tool to assess the impact of proposed flow regimes on the parasite, and it can be used for projecting the effects of alternative water management scenarios on disease-induced mortality of juvenile salmonids such as with an altered water temperature regime or with dam removal.

Биологические особенности нерестовой части популяции атлантического лосося (Salmo salar Linnaeus, 1758) бассейна реки Северная Двина

Salmon fishing in the lower reaches of the Northern Dvina River is based on the use of the spawning part of the Atlantic salmon population. Fisheries regulation measures are developed using knowledge of the biology of the species. Thus, the aim of the research is a comprehensive understanding of the biology of the spawning part of the salmon population in the Northern Dvina River basin based on the generalization of materials from commercial catches for the period 1931-2014. After feeding in the northeastern part of the Atlantic Ocean, adult salmon return to spawn at the age of 5+. The reproductive part of salmon populations is dominated by females. The average size and weight indicators of salmon making spawning migrations are 77,42 cm and 5,43 kg. It has been established that in the last decade of observations, the size and weight characteristics of the reproductive part of the Atlantic salmon populations in the Severodvinsk basin have stabilized. This allows us to conclude that there are effective measures to regulate the legal salmon fishery.

Thermal selection and delayed migration by adult sockeye salmon (Oncorhynchus nerka) following escape from simulated in-river fisheries capture

Two hypotheses were tested concerning the consequences to adult sockeye salmon (Oncorhynchus nerka) of escape from commonly used fishing gear (gillnet, seine net and tangle net). First, by experimentally exposing 214 fish to three commonly used fishing gear types (gillnets, tangle nets, or seine nets) and releasing to complete migration after PIT-tagging, we tested the hypothesis that migration success and behaviour are differentially impacted according to the type of fishing gear interaction and escape. Also, by fitting salmon with thermal loggers, we tested whether salmon behaviourally selected cooler lake water following an escape encounter. Migration success was unaffected after escape from the simulated gear types compared to control fish. Surviving sockeye salmon that had gillnet or seine net encounter, but not a tangle net encounter, on average took approximately 2 days longer to migrate to the spawning area (averaging 14.7 days and 14.9 days, respectively) compared to control fish (12.6 days). Furthermore, escaped fish migrated at cooler temperatures through a lake system (average of 14.0 °C) compared to control fish (15.3 °C), which would reduce their absolute cost of transport during this migration by reducing the standard metabolic rate by about 10%. Consequently, in addition to demonstrating that fish escapement from a fishing gear will alter their subsequent migration behaviour, we introduce the possibility that the associated increase in energy expenditure and migration delay can be partially compensated for by behavioural selection of cooler water, if it is available, to lower basic energy turnover in a fish that is entirely reliant on energy stores to fuel its spawning migration.

Origin, Postrelease Survival, and Imprinting of Pen‐Acclimated and Direct‐Stocked Chinook Salmon in Lake Ontario

AbstractWe determined the stocking origin of the Chinook Salmon Oncorhynchus tshawytscha harvest and compared the relative survival and tributary returns of pen‐acclimated and direct‐stocked salmon at eight sites in Lake Ontario. Chinook Salmon parr were coded‐wire‐tagged in 2010, 2011, and 2013, and adult salmon were recovered in the lake and tributaries from 2011 to 2017. Lake harvest counts indicated that pen acclimation provided significantly better smolt‐to‐lake harvest survival, with averages of 1.7, 2.3, and 2.3 times greater contribution (SE = 0.15, 0.21, 0.23), respectively, to the lake fishery than direct stocking. After accounting for lake survival, pen acclimation also provided significantly better smolt‐to‐adult return rates to tributary harvest than direct stocking at some sites, with average return ratios of 0.8, 1.1, and 1.6 (SE = 0.2, 0.2, 0.3), respectively, for the three year‐classes. Port‐specific lake harvest from June to August consisted of salmon stocked at sites throughout the lake, indicating a well‐mixed population prior to the prespawn staging period. Of the eight lake ports analyzed, a minority of the Chinook Salmon harvested by anglers in June–August were stocked at each site (mean = 13%, SE = 2%) or at nearby sites (mean = 22%, SE = 4%), with most originating from stocking sites greater than 30 km away. In September, stocked Chinook Salmon became more segregated in the lake, with harvest at each site consisting of a higher percentage (mean = 38%, SE = 4%) of salmon stocked at those sites and nearby sites (mean = 29%, SE = 5%), suggesting that salmon began staging in this period. In contrast, most salmon harvested by tributary anglers in October were stocked at those sites (mean = 67%, SE = 4%), indicating good imprinting of both pen‐acclimated and direct‐stocked Chinook Salmon. Most strays in tributaries were from nearby stocking sites. Increased Chinook Salmon catch rates in the lake fishery coincided with increased use of pen acclimation and a declining prey fish population, underscoring the importance of evaluating outcomes of new stocking policies that may increase predator survival and predation pressure on prey.

Estimating Adult Pacific Salmon Energy Use in Coastal British Columbia and the Fraser River Estuary with Acoustic Accelerometer Transmitters

Estimating Adult Pacific Salmon Energy Use in Coastal British Columbia and the Fraser River Estuary with Acoustic Accelerometer Transmitters

First juvenile chum salmon confirms successful reproduction for Pacific salmon in the North American Arctic

The distributional extent of Pacific salmon (Oncorhynchus spp.) in the North American Arctic is unresolved. While adult Pacific salmon have a recurring presence across the Alaskan North Slope and into the Canadian Arctic, it is uncertain if these fish are part of established Arctic populations, vagrants from outside sources reproducing unsuccessfully, or both. Here we present the first confirmed record of a juvenile chum salmon (Oncorhynchus keta) captured in the nearshore marine ecosystem in the North American Arctic. This provides the first scientific evidence of successful spawning and early marine survival of Pacific salmon in the North American Arctic. It was caught near Kaktovik, Alaska, in August 2017 with a group of similarly sized age-0 Mackenzie River Arctic cisco (Coregonus autumnalis). Stable isotope and otolith microchemistry analyses are consistent with use of the nearshore estuarine corridor from the Mackenzie River west along the northern coast. This contributes critical information needed to identify, manage, and conserve biodiversity at the northern range edge and will help to clarify the status of Pacific salmon as potentially emerging fisheries develop in the North American Arctic due to climate warming.

Strong Parallel Differential Gene Expression Induced by Hatchery Rearing Weakly Associated with Methylation Signals in Adult Coho Salmon (O. kisutch).

Human activities and resource exploitation led to a massive decline of wild salmonid populations, consequently, numerous conservation programs have been developed to supplement wild populations. However, many studies documented reduced fitness of hatchery-born relative to wild fish. Here, by using both RNA sequencing and Whole Genome Bisulfite Sequencing of hatchery and wild-born adult Coho salmon (Oncorhynchus kisutch) originating from two previously studied river systems, we show that early-life hatchery-rearing environment-induced significant and parallel gene expression differentiation is maintained until Coho come back to their natal river for reproduction. A total of 3,643 genes differentially expressed and 859 coexpressed genes were downregulated in parallel in hatchery-born fish from both rivers relative to their wild congeners. Among those genes, 26 displayed a significant relationship between gene expression and the median gene body methylation and 669 single CpGs displayed a significant correlation between methylation level and the associated gene expression. The link between methylation and gene expression was weak suggesting that DNA methylation is not the only player in mediating hatchery-related expression differences. Yet, significant gene expression differentiation was observed despite 18 months spent in a common environment (i.e., the sea). Finally, the differentiation is observed in parallel in two different river systems, highlighting the fact that early-life environment may account for at least some of the reduced fitness of the hatchery salmon in the wild. These results illustrate the relevance and importance of considering both epigenome and transcriptome to evaluate the costs and benefits of large-scale supplementation programs.

Art’s Work in the Age of Biotechnology: Shaping Our Genetic Futures

Art’s Work in the Age of Biotechnology: Shaping Our Genetic Futures

Larval salmon lice Lepeophtheirus salmonis exhibit behavioral responses to conspecific pre-adult and adult cues.

In the larval stage of the parasitic copepod Lepeophtheirus salmonis, the free-living copepodid must locate and settle on a salmonid host. Chemosensory mechanisms play a role in determining whether a potential host is suitable for attachment, yet the full suite of chemical cues and resulting behavioral mechanisms used are unknown. After maturing, pre-adult female and adult male salmon lice aggregate upon salmonid hosts for reproduction. Copepodid salmon lice have been observed preferentially infesting hosts that harbor conspecific adults. The aim of this study was to investigate the possibility that salmon lice copepodids perceive and respond to cues from pre-adult female, adult-male, and/or gravid female salmon lice. Behavioral bioassays were conducted in vitro with copepodids exposed to water conditioned with 3 stages of conspecific lice (pre-adult female, adult male, or gravid female), and seawater conditioned with Atlantic salmon Salmo salar Linnaeus, 1758. Experiments demonstrated that copepodids exposed to water conditioned with the salmon host, pre-adult female, or adult male salmon lice significantly altered their behavior, whereas salmon lice exposed to water conditioned with gravid females did not. These results are potentially valuable in the development of novel methods for mitigation of L. salmonis in the salmon aquaculture industry.

Modeling and Control Design for an Autonomous Underwater Vehicle Based on Atlantic Salmon Fish

Biologically inspired autonomous underwater vehicles (AUVs) or biomimetic AUVs are made to replicate the structural and physiological features of aquatic species. Thus, incorporation of its design in AUV modelling provides higher efficiency at low speeds and improves maneuverability and controllability. This paper develops a biomimetic AUV design based on structural parameters and physiology of an adult Atlantic Salmon fish and proposes a robust control scheme for propelling the fins. For the biomimetic model design of AUV, a 3D CAD model is developed using the actual parameters of Atlantic Salmon fish. The hydrodynamic analysis is performed to calculate the effect of different angles of fin orientations on the value of drag and lift coefficients. Further, kinematic analysis of the tail propulsion system is carried out using the Denavit Hartenberg convention in the Matlab®. Based on the obtained modeling parameters of AUV, a robust sliding mode controller is proposed for tracking the desired tail propulsion response using a DC motor under model uncertainties and disturbances. Moreover, the closed-loop asymptotic stability is also guaranteed through Lyapunov theory, which ensures the convergence of system states to the desired angular movement. Lastly, the proposed algorithm is validated using simulation results with comparative performance analysis to illustrate its efficacy.

Low summer river flows associated with low productivity of Chinook salmon in a watershed with shifting hydrology

Abstract Climate change and human activities are transforming river flows globally, with potentially large consequences for freshwater life. To help inform watershed and flow management, there is a need for empirical studies linking flows and fish productivity. We tested the effects of river conditions and other factors on 22 years of Chinook salmon productivity in a watershed in British Columbia, Canada. Freshwater conditions during adult salmon migration and spawning, as well as during juvenile rearing, explained a large amount of variation in productivity. August river flows while salmon fry reared had the strongest effect on productivity—our model predicted that cohorts that experience 50% below average flow in the August of rearing have 21% lower productivity. These contemporary relationships are set within long‐term changes in climate, land use, and hydrology. Over the last century, average August river discharge decreased by 26%, air temperatures warmed, and water withdrawals increased. Seventeen percent of the watershed was logged in the last 20 years. Our results suggest that, in order to remain stable, this Chinook salmon population being assessed for legal protection requires substantially higher August flow than previously recommended. Changing flow regimes—driven by watershed impacts and climate change—can threaten imperilled fish populations.

Cultural and educational releases of salmon in areas blocked by major hydroelectric projects on the Columbia River

Abstract Salmon are revered by Pacific Northwest Tribes as a central figure in their cultural and spiritual identity and have been a critical food resource for millennia. Historic commercial overfishing and hydropower development on the Columbia River have devastated salmon runs and altered tribal communities. Before European settlement of North America, most Pacific Northwest Tribal economies were based on obtaining salmon for food and bartering for other commodities. Despite extensive efforts to promote salmon recovery in downstream areas, most salmon populations continue to struggle throughout the Columbia River Basin. Over 1,800 km of historical salmon habitat remain inaccessible upstream of Chief Joseph and Grand Coulee dams due to lack of fish passage at these facilities. The Indian Tribes of the upper Columbia Basin are working collectively on salmon reintroduction efforts through both a long-term scientific phased approach and near-term cultural and educational releases. This paper will briefly outline the Phased approach and provide detail on the initial results of some recent cultural and educational releases of salmon in the blocked area. The cultural and educational releases had a goal of reconnecting the people with the salmon and the salmon with historic habitats. These salmon release events were diverse and included school children releasing juvenile fish they raised in the classroom, releasing adult salmon to swim free and reproduce, and tribal members harvesting salmon from their ancestral waters. Ceremonies were held to celebrate the significance of salmon to the tribal cultures and the salmon's return home. In addition to the ceremonies, some fish were tagged to evaluate survival and behavior and to begin to document the effectiveness of trap and haul efforts. The effort resulted in anadromous salmon reintroduction to their traditional waters for the first time in 60 to 110 years. These efforts have generated tremendous interest from the press and given the people of the region a glimpse at what is possible, building momentum for the larger Phased reintroduction effort.

Protective Immunization of Atlantic Salmon (Salmo salar L.) against Salmon Lice (Lepeophtheirus salmonis) Infestation.

Vaccination against salmon lice (Lepeophtheirus salmonis) is a means of control that averts the negative effects of chemical approaches. Here, we studied the immunogenicity and protective effect of a vaccine formulation (based on a salmon lice-gut recombinant protein [P33]) against Lepeophtheirus salmonis infestation in Atlantic salmon in a laboratory-based trial. Our findings revealed that P33 vaccine can provide a measure of protection against immature and adult salmon lice infestation. This protection seemed to be vaccine dose-dependent, where higher doses resulted in lower parasitic infestation rates. We also provide immunological evidence confirming that P33-specific immune response can be triggered in Atlantic salmon after P33 vaccination, and that production of P33-specific antibodies in blood can be detected in vaccinated fish. The negative correlation between P33-specific IgM in salmon plasma and salmon lice numbers on vaccinated fish suggests that protection against lice can be mediated by the specific antibody in salmon plasma. The success of P33 vaccination in protecting salmon against lice confirms the possibility of employing the hematophagous nature of the parasite to deliver salmon-specific antibodies against lice-gut proteins.

Patterns in spatial use of land-locked Atlantic salmon (Salmo salar) in a large lake

Understanding the spatial use of reintroduced fish is useful for fisheries management and evaluating restoration success. Atlantic salmon (Salmo salar) were reintroduced into Lake Ontario in the 1990s; however, the movement ecology of these land-locked fish is unknown. Using acoustic telemetry and Floy tag mark-recaptures, we examined seasonal home range and space use of Atlantic salmon in Lake Ontario. Hatchery-raised adult Atlantic salmon were tagged with acoustic transmitters (n = 14; 8 with depth sensors) or Floy tags (n = 1915) and released. Both acoustic telemetry and Floy tag recaptures (n = 90) indicated cross lake movements, and home ranges encompassed nearly the entire lake in summer but was smaller in winter. Movements were nearshore (<2 km from shore) from spring to summer at ∼20 m bathymetric depths, with movements closer to shore in the fall, and further offshore (∼5.5 km from shore and 45 m bathymetric depths) in winter. Depth use was relatively shallow (<4 m) with occasional deeper dives (max = 28.5 m), and small diel vertical movements (1–5 m), moving deeper during daytime, consistent with ocean movements of Atlantic salmon. There appears to be spatial segregation among Atlantic salmon and other Lake Ontario salmonids, however, overlap likely occurs in nearshore waters during the spring. Wide-ranging movements of Atlantic salmon in binational (Canada/USA) waters reflects the importance of government agencies collaborating to ensure sustainable fisheries and the coordination of species restoration activities. This is the first study to provide detailed spatial use of Lake Ontario Atlantic salmon to assist in the management of this reintroduced species.