Juvenile Chinook Salmon Research Articles

Exposure to exogenous egg cortisol does not rescue juvenile Chinook salmon body size, condition, or survival from the effects of elevated water temperatures.

Climate change is leading to altered temperature regimes which are impacting aquatic life, particularly for ectothermic fish. The impacts of environmental stress can be translated across generations through maternally derived glucocorticoids, leading to altered offspring phenotypes. Although these maternal stress effects are often considered negative, recent studies suggest this maternal stress signal may prepare offspring for a similarly stressful environment (environmental match). We applied the environmental match hypothesis to examine whether a prenatal stress signal can dampen the effects of elevated water temperatures on body size, condition, and survival during early development in Chinook salmon Oncorhynchus tshawytscha from Lake Ontario, Canada. We exposed fertilized eggs to prenatal exogenous egg cortisol (1,000 ng/ml cortisol or 0 ng/ml control) and then reared these dosed groups at temperatures indicative of current (+0°C) and future (+3°C) temperature conditions. Offspring reared in elevated temperatures were smaller and had a lower survival at the hatchling developmental stage. Overall, we found that our exogenous cortisol dose did not dampen effects of elevated rearing temperatures (environmental match) on body size or early survival. Instead, our eyed stage survival indicates that our prenatal cortisol dose may be detrimental, as cortisol‐dosed offspring raised in elevated temperatures had lower survival than cortisol‐dosed and control reared in current temperatures. Our results suggest that a maternal stress signal may not be able to ameliorate the effects of thermal stress during early development. However, we highlight the importance of interpreting the fitness impacts of maternal stress within an environmentally relevant context.

California Current seascape influences juvenile salmon foraging ecology at multiple scales

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 634:159-173 (2020) - DOI: https://doi.org/10.3354/meps13185 California Current seascape influences juvenile salmon foraging ecology at multiple scales Megan C. Sabal1,*, Elliott L. Hazen2, Steven J. Bograd2, R. Bruce MacFarlane3, Isaac D. Schroeder2,4, Sean A. Hayes5, Jeffrey A. Harding3, Kylie L. Scales2,4,6, Peter I. Miller7, Arnold J. Ammann3, Brian K. Wells3 1University of California Santa Cruz, Department of Ecology and Evolutionary Biology, Santa Cruz, CA 95060, USA 2Environmental Research Division, Southwest Fisheries Science Center, National Marine Fisheries Service, NOAA, Monterey, CA 93940, USA 3Southwest Fisheries Science Center, National Marine Fisheries Service, NOAA, Santa Cruz, CA 95060, USA 4Institute of Marine Sciences, University of California Santa Cruz, Santa Cruz, CA 95064, USA 5Northeast Fisheries Science Center, National Marine Fisheries Service, NOAA, Woods Hole, MA 02543, USA 6Global Change Ecology Research Group, School of Science and Engineering, University of the Sunshine Coast, Maroochydore, QLD 4556, Australia 7Remote Sensing Group, Plymouth Marine Laboratory, Plymouth PL1 3DH, UK *Corresponding author: msabal@ucsc.edu ABSTRACT: Juvenile salmon Oncorhynchus spp. experience variable mortality rates during their first few months in the ocean, and high growth during this period is critical to minimize size-selective predation. Examining links between the physical environment and foraging ecology is important to understand mechanisms that drive growth. These mechanisms are complex and include interactions among the physical environment, forage availability, bioenergetics, and salmon foraging behavior. Our objectives were to explore how seascape features (biological and physical) influence juvenile Chinook salmon O. tshawytscha foraging at annual and feeding-event scales in the California Current Ecosystem. We demonstrate that forage abundance was the most influential determinant of mean salmon stomach fullness at the annual scale, while at the feeding-event scale, fullness increased with greater cumulative upwelling during the 10 d prior and at closer distances to thermal fronts. Upwelling promotes nutrient enrichment and productivity, while fronts concentrate organisms, likely resulting in available prey to salmon and increased stomach fullness. Salmon were also more likely to consume krill when there was high prior upwelling, and switched to non-krill invertebrates (i.e. amphipods, decapods, copepods) in weaker upwelling conditions. As salmon size increased from 72-250 mm, salmon were more likely to consume fish, equal amounts of krill, and fewer non-krill invertebrates. Broad seascape processes determined overall prey availability and fullness in a given year, while fine- and meso-scale processes influenced local accessibility of prey to individual salmon. Therefore, processes occurring at multiple scales will influence how marine organisms respond to changing environments. KEY WORDS: Salmon diets · Fullness · Krill · Upwelling · Fronts · Retention Full text in pdf format Supplementary material PreviousNextCite this article as: Sabal MC, Hazen EL, Bograd SJ, MacFarlane RB and others (2020) California Current seascape influences juvenile salmon foraging ecology at multiple scales. Mar Ecol Prog Ser 634:159-173. https://doi.org/10.3354/meps13185 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 634. Online publication date: January 23, 2020 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2020 Inter-Research.

Limitations of Active Removal to Manage Predatory Fish Populations

AbstractPrograms to control predatory fishes have successfully increased the survival of imperiled prey fishes in some cases, but efficacy depends on the population dynamics and ecological interactions between the predators, prey, and the rest of the community. In California's Sacramento–San Joaquin Delta, extremely low survival of downstream‐migrating juvenile salmonids has been ascribed in part to predation by abundant nonnative fishes that have become naturalized in the system. This study aimed to determine the effectiveness of removing some of these predatory fish to increase the survival of juvenile salmonids in the San Joaquin River. In 2014 and 2015, we used predation event recorders (PERs) to estimate predation rates before and after localized, experimental predatory fish removals and additions. We also estimated survival of juvenile Chinook SalmonOncorhynchus tshawytschabefore and after predator manipulations in 2014 using acoustic tags. We found no statistically significant evidence for an effect of predator removals or additions on survival rates of Chinook Salmon (as measured by acoustic tags) or on predation rates (as measured byPERs), despite a one‐time reduction of approximately 40–70% of all predators from “removal” sites and relocation to “addition” sites. We review examples of successful predator control programs elsewhere, highlighting key differences between those programs and our study in the Sacramento–San Joaquin Delta.

Magnetoreception in fishes: the effect of magnetic pulses on orientation of juvenile Pacific salmon.

A variety of animals sense Earth's magnetic field and use it to guide movements over a wide range of spatial scales. Little is known, however, about the mechanisms that underlie magnetic field detection. Among teleost fish, growing evidence suggests that crystals of the mineral magnetite provide the physical basis of the magnetic sense. In this study, juvenile Chinook salmon (Oncorhynchus tshawytscha) were exposed to a brief but strong magnetic pulse capable of altering the magnetic dipole moment of biogenic magnetite. Orientation behaviour of pulsed fish and untreated control fish was then compared in a magnetic coil system under two conditions: (1) the local magnetic field and (2) a magnetic field that exists near the southern boundary of the natural oceanic range of Chinook salmon. In the local field, no significant difference existed between the orientation of the control and pulsed groups. By contrast, orientation of the two groups was significantly different in the magnetic field from the distant site. These results demonstrate that a magnetic pulse can alter the magnetic orientation behaviour of a fish and are consistent with the hypothesis that salmon have magnetite-based magnetoreception.

Impact of Vertically-Suspended Environmental Enrichment and Two Densities of Fish on Circular Tank Velocity Profiles

Vertically-suspended environmental enrichment has been shown to produce improvements in fish growth during hatchery rearing in circular tanks. This study documented the effects of a novel suspended structure on the velocity profile of a 3.63-m diameter circular tank containing juvenile landlocked fall Chinook salmon (Oncorhynchus tshawytscha) at two different densities (9.0 and 34.3 kg/m3). The addition of vertically-suspended structure to the tank significantly decreased velocities at nearly every sampling point, with velocities typically dropping from 15 cm/s without structure to less than 6 cm/s when structure was present. Fish density also significantly impacted in-tank velocities, with an inverse relationship observed between the density of fish and water velocity. Significant interactions were present among the presence or absence of structure and fish density. When structure and fish were absent, the velocity at the edge of the tank was 15.63 cm/s, which was significantly higher than the 4.75 cm/s velocity when both structure and the lower fish density were added, which was in turn significantly higher than the 2.29 cm/s velocity observed with structure and higher fish density. Despite the potentially unique features of this study, vertically-suspended environmental enrichment and the presence of fish clearly alter circular tank water velocities, which may at least partially explain the improvements in fish rearing performance observed with the use of suspended structure.

Influence of Maternally‐Transferred Nitrogen and Carbon on Stable Isotope Ratios in Juvenile Chinook Salmon

AbstractIn freshwater fishes, the nitrogen and carbon stable isotopes ratios in tissues commonly reflect the environment in which a fish is feeding, assimilated through its diet. For many species, small‐bodied or younger individuals generally feed lower in the food chain, while large‐bodied mature individuals feed at higher trophic levels. This is reflected in the stable isotope (SI) ratios within fish tissue, with large‐bodied fish typically exhibiting more enriched isotope signatures. However, an inverse relationship has been seen in recently‐hatched, premigratory juvenile fishes of anadromous maternal stock. This has been documented previously in some salmonids, and it is due to the maternal contribution of marine‐derived nitrogen to juvenile fish, which fades with isotopic turnover as they grow and assimilate energy from freshwater food webs. However, this phenomenon has not been previously documented for wild Pacific salmonids, as we present here. We found that the isotope ratios of premigratory juvenile Chinook Salmon Oncorhynchus tshawytscha were elevated at posthatch, declined with increased body size, and converged with those of sympatric freshwater resident Brown Trout at 3.39 g body mass or 79 mm TL (at approximately 48–84 d posthatch). Given our findings, researchers should account for the lingering maternal isotopic enrichment of premigratory juvenile salmon to avoid introducing bias into SI‐based freshwater food web studies. Additionally, the maternal life history (sea‐run or resident) for the progeny of partially anadromous Pacific salmonids can likely be classified by examining SI information, which is supported by our results and by previous research on other anadromous salmonids. Therefore, SI analysis could be a useful tool for characterizing the relative contribution of anadromous females in partially migratory populations of other Pacific salmonids (e.g., steelhead Oncorhynchus mykiss) to help with the management and conservation of these sensitive fish species.

Characterizing Juvenile Chinook Salmon Residency and Early Growth in the Lower Fraser River Estuary

Characterizing Juvenile Chinook Salmon Residency and Early Growth in the Lower Fraser River Estuary

Assessing the Early Marine Ecology of Juvenile Chinook Salmon in a Warming Bering Sea

Assessing the Early Marine Ecology of Juvenile Chinook Salmon in a Warming Bering Sea

Spatial variation of juvenile Chinook Salmon (Oncorhynchus tshawytscha) survival in a modified California river

Spatial variation in habitat structure is a well-recognized characteristic of lotic ecosystems. The resulting patchwork mosaic provides opportunities for growth and survival as well as mortality risks for fish migrating through these systems. Dam construction within a watershed has numerous downstream tail water effects that alter creation and evolution of habitat features used by anadromous fishes that spawn and rear in these reaches. California Central Valley Pacific salmon (Oncorhynchus spp) are largely restricted to areas below impassable dams and these populations are undergoing widespread declines. High mortality of juvenile salmon in these reaches is thought to be a limitation to recovery. We conducted a radio telemetry study to evaluate spatial variation in juvenile Chinook Salmon (O. tschawytscha) survival and survival-environment relationships in three reaches of a Central Valley tail water. Additionally, we used mobile surveys to identify the location of last known detections to elucidate areas of disproportionate mortality. Our results indicated variation in flow and salmon size had greater explanatory power than year effects. However, relationships between flow, salmon size and survival were reach-specific indicating drivers of survival are spatially heterogeneous. Significant clumping of last known detections in the two lower reaches of the river suggests that mortality may be more frequent in these locations. Our results suggest that there is substantial spatial variation in migration mortality and both environmental conditions (flow) and salmon characteristics (size) have a strong influence on observed mortality. This information should be used to target actions that can support Chinook Salmon recovery.

Carcass additions increase juvenile salmonid growth, condition, and size in an interior Columbia River Basin tributary

Numbers of anadromous fish returning to freshwater ecosystems have declined precipitously across much of western North America, reducing a potentially important resource subsidy for juvenile salmonids. We added carcasses to three sections of a Snake River tributary and assessed juvenile Chinook salmon (Oncorhynchus tshawytcha) and steelhead trout (Oncorhynchus mykiss) growth, body condition, size, and diet responses in summer and early fall. Juvenile salmonids consumed an abundance of eggs and carcass tissue, which increased energy rations. Within 3 weeks of carcass additions, juvenile Chinook and steelhead growth rates were 1.1–5 and 6–23 times greater in treatment reaches relative to control reaches, respectively. We used long-term tagging and detection data from this system to assess the relationship between juvenile Chinook size and emigration survival for two different juvenile life histories. The increased growth rates and body size in response to carcass additions, coupled with a positive relationship between body size and survival, suggest that juvenile salmonid rearing productivity and emigration survival may be limited by depressed returns of anadromous fishes in this system and potentially other tributaries of the Columbia Basin.

Chemical tracers guide identification of the location and source of persistent organic pollutants in juvenile Chinook salmon (Oncorhynchus tshawytscha), migrating seaward through an estuary with multiple contaminant inputs

Understanding the spatial extent, magnitude, and source of contaminant exposure in biota is necessary to formulate appropriate conservation measures to reduce or remediate contaminant exposure. However, obtaining such information for migratory animals is challenging. Juvenile Chinook salmon (Oncorhynchus tshawytscha), a threatened species throughout the US Pacific Northwest, are exposed to persistent organic pollutants (POPs), including polybrominated diphenyl ether (PBDE) flame retardants and polychlorinated biphenyls (PCBs), in many developed rivers and estuaries. This study used three types of complementary chemical tracer data (contaminant concentrations, POP fingerprints, and stable isotopes), to determine the location and source of contaminant exposure for natural- and hatchery-origin Chinook salmon migrating seaward through a developed watershed with multiple contaminant sources. Concentration data revealed that salmon were exposed to and accumulated predominantly PBDEs and PCBs in the lower mainstem region of the river, with higher PBDEs in natural- than hatchery-origin fish but similar PCBs in both groups, associated with differences in contaminant inputs and/or habitat use. The POP fingerprints of the natural-origin-fish captured from this region were also distinct from other region and origin sample groups, with much higher proportions of PBDEs in the total POP concentration, indicating a different contaminant source or habitat use than the hatchery-origin fish. Stable isotopes, independent tracers of food sources and habitat use, revealed that natural-origin fish from this region also had depleted δ15N signatures compared to other sample groups, associated with exposure to nutrient-rich wastewater. The PBDE-enhanced POP fingerprints in these salmon were correlated with the degree of depletion in nitrogen stable isotopes of the fish, suggesting a common wastewater source for both the PBDEs and the nitrogen. Identification of the location and source of contaminant exposure allows environmental managers to establish conservation measures to control contaminant inputs, necessary steps to improve the health of Chinook salmon and enhance their marine survival.

How Small Can We Go? Evaluating Survival, Tag Retention, and Growth of Juvenile Chinook Salmon Implanted with a New Acoustic Microtag

AbstractRecently, an acoustic microtag, called the Eel–Lamprey Acoustic Tag (ELAT), was developed for use in juvenile American Eel Anguilla rostrata and Pacific Lamprey Entosphenus tridentatus. The ELAT (12.0 × 2.0 mm; 0.088 g in air) has the potential to be used to study other small‐bodied fishes. In this pilot study, juvenile Chinook Salmon Oncorhynchus tshawytscha 52–99 mm fork length (FL) were surgically implanted with an ELAT (n = 99) or remained untagged (control; n = 101). Fish were held for 30 d to evaluate survival, tag retention, and growth. Survival did not differ significantly between control (n = 98 or 97.0%) and tagged fish (n = 95 or 95.9%). Logistic regression analysis suggested that survival was influenced by initial FL and tag burden. Mortalities only occurred in tagged fish with initial FLs of ≤65 mm (FL range = 57–65 mm; tag burdens = 3.8–5.9%). However, a tagged fish with an initial FL of 62 mm or an initial tag burden of 4.1% (FL range = 58–64 mm) was predicted to have a 90% chance of survival, and the smallest fish that survived the study was 54 mm FL (1.8 g; tag burden = 4.9%). Tag retention was high (99%), with only one fish expelling an ELAT during the study. Control fish grew slightly larger than the tagged individuals, but differences in final pooled FLs and weight gains were not significant. Our results demonstrate the successful surgical implantation of the ELAT into Chinook Salmon as small as 54 mm FL (1.8 g).

Relating survival of fall-run Chinook Salmon through the San Joaquin Delta to river flow

Survival of juvenile fall-run Chinook Salmon Oncorhynchus tshawytscha from the San Joaquin River (SJR) during their migration through the Sacramento-San Joaquin Delta of California has been low in recent years, and there is uncertainty about the role of river flow on survival. Five years (2010–2014) of acoustic telemetry data from juvenile hatchery-reared salmon offer spatially detailed survival information through this region. Multinomial regression and generalized linear models were used to relate survival to river flow in the SJR and its distributary, Old River (OR), on various spatial and temporal scales. Higher survival to Delta exit (rkm 77 from Golden Gate Bridge) was associated with higher root mean square of OR flow in the strongly tidal interior Delta (rkm 123; P < 0.0001), but not with higher SJR flow either entering the Delta from upstream (rkm 196; P = 0.2795) or measured in the Delta near the riverine/tidal interface (rkm 150; P = 0.3845). Survival in the upstream, more riverine region of the Delta was positively associated with SJR flow measured at rkm 150 and average net flow in the interior Delta (P ≤ 0.0001 for each), suggesting different mechanisms driving survival in the upstream versus downstream reaches of the Delta. The spatial complexity of the survival-flow relationship suggests that efforts to maximize total Delta survival should focus on a sequence of smaller regions, tailoring management strategies to each region rather than a single strategy for the Delta as a whole. Highly variable environmental conditions in this region combined with very low survival require more data to fully address the complex survival-flow relationship, both more years of data on various spatial scales and larger sample sizes of acoustic-tagged fish.

Movement and Apparent Survival of Acoustically Tagged Juveline Late-Fall Run Chinook Salmon Released Upstream of Shasta Reservoir, California

Stakeholder interests have spurred the reintroduction of the critically endangered populations of Chinook Salmon to tributaries upstream of Shasta Dam, in northern California. We released two groups of acoustically tagged, juvenile hatchery, late-fall Chinook Salmon to determine how juvenile salmon would distribute and survive. We measured travel times to Shasta Dam, and the number of fish that moved between locations within Shasta Reservoir. We used mark-recapture methods to determine detection and apparent survival probabilities of the tagged fish as they traveled through five reaches of the Sacramento River from the McCloud River to San Francisco Bay (~590 km) over the two 3-month observation periods. After our first (February) release of 262 tagged fish, 182 fish (70%) were detected at least once at the dam, 41 (16%) were detected at least once downstream of Shasta Dam, and 3&nbsp;(1%) traveled as far as San Francisco Bay. After the second (November) release of 355 tagged fish, only 4 (1%) were detected at Shasta Dam. No fish were detected below Shasta Dam, so we could not estimate survival for this second release group. The first release of fish was fortuitously exposed to exceptionally high river flows and dam discharges, which may have contributed to the more distant downstream migration and detection of these fish — though other factors such as season, diploid versus triploid, and fish maturation and size may have also contributed to release differences. The reported fish travel times as well as detection and survival rates are the first estimates of juvenile salmon emigration from locations above Shasta Dam in more than 70 years. This information should help inform resource managers about how best to assess juvenile winter-run Chinook Salmon and assist in their reintroduction to watersheds upstream of Shasta Dam.

GrowChinook: an optimized multimodel and graphic user interface for predicting juvenile Chinook salmon growth in lentic ecosystems

Linked foraging and bioenergetics models allow for increased understanding of fish growth potential and behavior by incorporating prey availability coupled to environmental conditions including temperature and prey visibility. To inform our understanding of growth and vertical migration patterns of Chinook salmon (Oncorhynchus tshawytscha) inhabiting lentic ecosystems, we linked foraging and bioenergetics models to create GrowChinook ( http://growchinook.fw.oregonstate.edu/ ). This multimodel design and optimization routine has broad applications in examining growth potential and predicting habitat use in stratified environments. We demonstrate the use of GrowChinook for the spring–summer rearing period in three Willamette River basin reservoirs, Oregon, USA. These reservoirs support juvenile spring Chinook salmon that exhibit a novel reservoir-reared life history that includes larger juvenile fish compared with nearby stream-reared subyearlings. Model outputs of predicted growth and depth use patterns based on observed prey distributions and environmental conditions were corroborated by observed empirical size and growth data from other years. Our simulations support diel vertical migration as a tactic that increases growth potential and contribute to understanding juvenile Chinook salmon growth in stratified systems.

Differential north–south response of juvenile Chinook salmon (Oncorhynchus tshawytscha) marine growth to ecosystem change in the eastern Bering Sea, 1974–2010

Abstract Chinook salmon (Oncorhynchus tshawytscha, Salmonidae) returns to western Alaska were historically high and variable but recently reached record lows. Understanding the differential influence of climatic and oceanic conditions on the growth of juvenile Chinook salmon in the north and south eastern Bering Sea is key to understanding mechanisms and factors affecting the production dynamics of Chinook salmon from western Alaska and the Arctic. Summer growth was lower and more variable among years for Chinook salmon in the south than the north eastern Bering Sea. Summer growth decreased with a rise in sea temperatures in the north and south and increased with more sea ice coverage and a later time of ice retreat in the south but not in the north. Capelin (Mallotus villosus), an important prey for juvenile Chinook salmon in the north and during cold years may link increased growth to cooler sea temperatures. Reduced and more variable summer growth of juvenile Chinook salmon from the eastern Bering Sea with warming may have implications on overwintering survival.

Endangered wild salmon infected by newly discovered viruses.

The collapse of iconic, keystone populations of sockeye (Oncorhynchus nerka) and Chinook (Oncorhynchus tshawytscha) salmon in the Northeast Pacific is of great concern. It is thought that infectious disease may contribute to declines, but little is known about viruses endemic to Pacific salmon. Metatranscriptomic sequencing and surveillance of dead and moribund cultured Chinook salmon revealed a novel arenavirus, reovirus and nidovirus. Sequencing revealed two different arenavirus variants which each infect wild Chinook and sockeye salmon. In situ hybridisation localised arenavirus mostly to blood cells. Population surveys of >6000 wild juvenile Chinook and sockeye salmon showed divergent distributions of viruses, implying different epidemiological processes. The discovery in dead and dying farmed salmon of previously unrecognised viruses that are also widely distributed in wild salmon, emphasizes the potential role that viral disease may play in the population dynamics of wild fish stocks, and the threat that these viruses may pose to aquaculture.

Low-Lipid Diets Fed at Reduced Ration: Effects on Growth, Body Composition, and Survival of Juvenile Chinook Salmon

Abstract There is a growing demand within research and conservation hatcheries to rear fish that more closely approximate the smaller size and leaner body composition of their wild counterparts. Low-lipid diets may help achieve this goal as they can provide all the nutritional needs of young fish and can lead to slower growth and leaner bodies. We compared growth of Chinook Salmon Oncorhynchus tshawytscha fed three experimental low-lipid diets (11–12, 8–9, 4–6% lipid) at the onset of feeding with a commercially available high-lipid diet (18–20%) and an experimentally formulated high-lipid control (13.9% lipid). After 5 mo on their respective treatments, the size, growth rate, and daily growth index of fish on the commercial diet were significantly higher than those on the three low-lipid diets. We also compared whole-body lipid content across our five diet treatments. Whole-body lipid content was significantly different across the five diets, with fish fed the commercial diet having, on average, an almost twofold higher lipid content over fish fed the lowest lipid diet formulation. We present comparable data from a limited sample of wild juvenile conspecifics as observations. We suggest that low-lipid starter diets can be used to produce healthy fish that more likely emulate some of the variations in size and body composition of wild fish.

Vertical Distribution of Juvenile Salmon in a Large Turbid River

Abstract We know very little about the vertical distribution of downstream-migrating juvenile Pacific salmon Oncorhynchus spp. in large rivers. It is important for project engineers and fisheries managers to understand the potential interactions of fishes with in-river hydrokinetic devices, which harness a river's energy by spinning a turbine to produce electrical current without damming or impounding water. Currently, several rural Alaskan communities are considering development projects for hydrokinetic devices, including projects in the Tanana River, near Nenana, Alaska. Therefore, the goal of this study was to determine the vertical distribution of juvenile Chinook Salmon Oncorhynchus tshawytscha, Coho Salmon Oncorhynchus kisutch, and Chum Salmon Oncorhynchus keta, in the Tanana River, at a site (bottom depth ∼ 8, channel width ∼ 150 m) where communities may deploy future hydrokinetic turbines. Using a suspended wingless fyke net system during diurnal periods (0800–1800 hours), we found juveniles of all three species at all depths of the water column and no significant differences in catch-per-unit-effort among four depth categories (surface, midwater, deep water, bottom water). The occurrence of juvenile salmon throughout the water column indicates that they may interact with hydrokinetic devices, regardless of their depth. Future research to more comprehensively characterize fish distribution patterns and describe the outcomes of fish–turbine interactions may inform practices aimed at reducing potentially deleterious impacts of hydrokinetic devices on juvenile Pacific salmon.

Fish Response to Turbulence Generated Using Multiple Randomly Actuated Synthetic Jet Arrays

Hydroelectric power stations generate turbulent flow conditions, which represent a potentially significant hydraulic stressor to fish passing through the turbine system. A test facility has been developed using two randomly actuated synthetic jet arrays (RASJAs) of 25 independent submersible pumps to generate a turbulent flow field for biological dose-response testing. The novel elements of this approach include the ability to control the exposure duration within a test volume due to low mean flow velocity as well as the capacity to scale the turbulence levels as a function of pump capacity. Juvenile Chinook salmon (Oncorhynchus tshawytscha) were subjected to the turbulent flow regime with average turbulence kinetic energy per unit mass of 0.089 m 2 / s 2 for periods of 2 min and 10 min. No significant loss of equilibrium or disorientation was observed after exposure for either duration at the level of turbulence achieved in this prototype. Further scaling of this approach is required to generate a complete dose-response relationship.