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At least 109 records · Page 6Linked to original sources
USGS2016

Predation on Pacific salmonid eggs and carcass's by subyearling Atlantic salmon in a tributary of Lake Ontario

A binational effort to reintroduce Atlantic salmon ( Salmo salar ) that were extirpated in the Lake Ontario ecosystem for over a century is currently being undertaken by the New York State Department of Environmental Conservation and the Ontario Ministry of Natural Resources. Reintroduction actions include the release of several life stages including fry, fall fingerlings, and yearling smolts. In this study we describe the diet of recently released fall fingerling Atlantic salmon in a tributary of the Salmon River, New York. A specific objective of the study was to determine if juvenile Atlantic salmon would utilize the high caloric food source provided by introduced Pacific salmonids ( Oncorhynchus spp .) that includes eggs and carcass flesh. Salmon eggs and carcass flesh comprised 20.5% of the October to January diet in 2013–14 and 23.9% in 2014–15. The consumption of steelhead ( O. mykiss ) eggs was a major part of the diet in April in both 2014 (54.1%) and 2015 (33.2%). This study documented that recently released Atlantic salmon will consume the high caloric food material provided by Pacific salmonids and that the consumption of this material extends for several months.

New York↗
USGS2016

Spatial and temporal heterogeneity of infectious hematopoietic necrosis virus in Pacific Northwest salmonids

The aquatic rhaboviral pathogen infectious hematopoietic necrosis virus (IHNV) causes acute disease in juvenile fish of a number of populations of Pacific salmonid species. Heavily managed in both marine and freshwater environments, these fish species are cultured during the juvenile stage in freshwater conservation hatcheries, where IHNV is one of the top three infectious diseases that cause serious morbidity and mortality. Therefore, a comprehensive study of viral genetic surveillance data representing 2590 field isolates collected between 1958 and 2014 was conducted to determine the spatial and temporal patterns of IHNV in the Pacific Northwest of the contiguous United States. Prevalence of infection varied over time, fluctuating over a rough 5–7 year cycle. The genetic analysis revealed numerous subgroups of IHNV, each of which exhibited spatial heterogeneity. Within all subgroups, dominant genetic types were apparent, though the temporal patterns of emergence of these types varied among subgroups. Finally, the affinity or fidelity of subgroups to specific host species also varied, where UC subgroup viruses exhibited a more generalist profile and all other subgroups exhibited a specialist profile. These complex patterns are likely synergistically driven by numerous ecological, pathobiological, and anthropogenic factors. Since only a few anthropogenic factors are candidates for managed intervention aimed at improving the health of threatened or endangered salmonid fish populations, determining the relative impact of these factors is a high priority for future studies.

Infection, Genetics and Evolution↗
USGS2016

A comparative examination of cortisol effects on muscle myostatin and HSP90 gene expression in salmonids

Cortisol, the primary corticosteroid in teleost fishes, is released in response to stressors to elicit local functions, however little is understood regarding muscle-specific responses to cortisol in these fishes. In mammals, glucocorticoids strongly regulate the muscle growth inhibitor, myostatin, via glucocorticoid response elements (GREs) leading to muscle atrophy. Bioinformatics methods suggest that this regulatory mechanism is conserved among vertebrates, however recent evidence suggests some fishes exhibit divergent regulation. Therefore, the aim of this study was to evaluate the conserved actions of cortisol on myostatin and hsp90 expression to determine if variations in cortisol interactions have emerged in salmonid species. Representative salmonids; Chinook salmon (Oncorhynchus tshawytscha), cutthroat trout (Oncorhynchus clarki), brook trout (Salvelinus fontinalis), and Atlantic salmon (Salmo salar); were injected intraperitoneally with a cortisol implant (50 lg/g body weight) and muscle gene expression was quantified after 48 h. Plasma glucose and cortisol levels were significantly elevated by cortisol in all species, demonstrating physiological effectiveness of the treatment. HSP90 mRNA levels were elevated by cortisol in brook trout, Chinook salmon, and Atlantic salmon, but were decreased in cutthroat trout. Myostatin mRNA levels were affected in a species, tissue (muscle type), and paralog specific manner. Cortisol treatment increased myostatin expression in brook trout (Salvelinus) and Atlantic salmon (Salmo), but not in Chinook salmon (Oncorhynchus) or cutthroat trout (Oncorhynchus). Interestingly, the VC alone increased myostatin mRNA expression in Chinook and Atlantic salmon, while the addition of cortisol blocked the response. Taken together, these results suggest that cortisol affects muscle-specific gene expression in species-specific manners, with unique Oncorhynchus-specific divergence observed, that are not predictive solely based upon mammalian stress responses.

General and Comparative Endocrinology↗
USGS2026

Time course of effects and tissue concentrations of 6PPDQ in three sensitive salmonids with additional data for two centrarchid species

Studies of 6PPD-quinone (6PPDQ) toxicity have identified both sensitive and resistant salmonid species at environmentally relevant concentrations. However, comparisons between species are complicated by varying testing conditions, which can limit the application to derivation of environmental quality guidelines. Furthermore, few studies have reported 6PPDQ tissue concentrations in fish with known exposure concentrations. Using standard methods with flow-through exposures to provide stable 6PPDQ concentrations, we compared time courses of mortality in three sensitive salmonid species (coho salmon Oncorhynchus kisutch , brook trout Salvelinus fontinalis , rainbow trout Oncorhynchus mykiss ), evaluated the potential for latent (delayed) mortality, and measured tissue concentrations in both fish that died during exposure and those that survived an additional 7 days in clean water. Further experiments documented insensitivity in two centrarchids (smallmouth bass Micropterus dolomieu and largemouth bass Micropterus nigricans ). Our study provided evidence for two mortality time courses: one in which nearly all mortality occurs in the first 24 h and one in which mortalities continue to accumulate throughout the exposure, and 96-h and 24-h LC50s are quite different. We did not observe evidence for the delayed onset of mortality due to 6PPDQ exposure. Most fish that survived exposure had undetectable 6PPDQ concentrations after 1 week in clean water, potentially informing biomonitoring strategies for wild populations.

Environmental Science & Technology↗
USGS2025

Salmonid sensory system development is affected by climate change driven temperature increases

Increases in water temperature due to global climate change are known to alter the course and timing of fish development. The mechanosensory lateral line (LL) system mediates flow-sensing behaviors vital for survival in fishes, but the effects of increased water temperatures resulting from climate change on its development have not been examined. Here LL development was documented in a cold-water salmonid (brook trout, Salvelinus fontinalis ) reared at the thermograph of a long-term study stream (ambient) and two higher temperatures (+ 2 and + 4 °C) that reflect projected increases within their native range. At these two higher temperatures, fish reach crucial early life history transitions earlier (e.g., hatch, “swim-up” from gravel nests into the water column) and are larger in size through the parr (juvenile) stage. Early forming canal neuromast receptor organs are larger, and the process of canal morphogenesis is also accelerated suggesting potential consequences for neuromast function and presumably for LL-mediated behaviors. A potential mismatch between the timing of transitions in early life history stages, the ability to carry out LL-mediated behaviors (e.g., prey detection), and the timing of the seasonal emergence of their preferred prey, could have serious implications for cold-water salmonid ecology and survival.

Scientific Reports↗
USGS2005

Habitat associations of age-0 cutthroat trout in a spring stream improved for adult salmonids

Native cutthroat trout ( Oncorhynchus clarki ) in the Snake River watershed use streams formed by large springs for spawning and nursery habitat. Several spring streams have been modified to enhance abundance of adult salmonids, but the habitat associations of age-0 cutthroat trout in these systems are undescribed. We assessed the frequency of collection of age-0 cutthroat trout in riffles, riffle margins, pool margins, and backwaters from late June to the middle of August 2000 in a spring stream with such modifications. The proportion of sites in which age-0 cutthroat trout were collected increased up to the middle of July and then decreased. We found substantially lower frequencies of collection of age-0 cutthroat trout in riffles compared to the three stream-margin habitat types. Age-0 cutthroat trout appeared to select shallow, low-velocity, stream-margin habitat with cover that provided protection from piscivorous adult salmonids and avian predators. Our observations suggest that modification of spring streams for production of cutthroat trout should include efforts to manage stream margins so they provide cover in the form of aquatic macrophytes or overhanging vegetation for age-0 fish.

Journal of Freshwater Ecology↗
USGS1957

The nutrition of salmonid fishes. I. Chemical and histological studies of wild and domestic fish

Salmonids reared under artificial conditions show marked consistent differences in body composition in comparison with wild salmonids. Protein and mineral levels are lower and lipid values are higher in hatchery fish than in wild fish. As the period of artificial rearing is increased, these differences become more extreme. In hatchery fish, there is generally more microscopically visible fat in the liver and viscera than in these organs in wild fish although extremes are seen in both groups. In young hatchery fish and in wild fish, there is no correlation between fat deposition in the liver and in the pancreas, but in older hatchery fish, both of these organs are fatty and there is a simultaneous increase in total body lipid. In wild fish, ceroid deposition is greater, suggesting that the fatty acids are more highly unsaturated. There is little difference in disease incidence between the two groups, but parasitism is more pronounced in wild fish. The significant variables between wild and artificially produced fish appear to be limited to diet and environment. From the factors discussed above, diet alone is probably the most important single factor in producing the changes observed in body composition.

Alaska, British Columbia, California, Oregon, Wash↗
USGS1957

The nutrition of salmonid fishes. II. Studies on production diets

In 69 production diets fed to hatchery salmonids, there was a wide variation in the ingredients of the diets and in their content of protein, fat, carbohydrate and ash. There was a close correlation between the body composition of hatchery-raised fish and the composition of the diets fed. The data indicated, however, that differences in hatchery management, such as level of feeding, were also important contributing factors in producing the observed body composition of hatchery fish. Wild fish had a markedly different body composition characterized by a much lower level of fat and relatively higher protein and mineral content The effect on survival of differences in body composition between wild and hatchery fish is discussed. There is a clearly defined need for additional research on the nutritional requirements of salmonids, the relationship between body composition and ability to survive, and for quality control in hatchery nutrition.

Journal of Nutrition↗
USGS2026

Beyond pro-vs-anti hatchery: A typology of fishing community perceptions of salmonid hatcheries in Oregon

Objectives: Pacific salmon and steelhead hatcheries are central to fisheries management along the West Coast of North America, yet they remain a source of persistent controversy. While often framed in binary terms of pro- or anti-hatchery, public perspectives are more nuanced. Methods: We conducted 18 in-depth interviews with members of Oregon’s non-tribal fishing communities, including recreational anglers, professional fishers, non-governmental organizations, hatchery workers, and policymakers, to explore perceptions of salmonid hatcheries. Results: We developed a typology of perceptions of salmonid hatcheries in Oregon, identifying five distinct belief-based types, which we label Advocates, Reformers, Balancers, Skeptics, and Restorers. These types differed in how they evaluated hatcheries’ social and ecological impacts, governance legitimacy, and management acceptability. While Advocates and Reformers emphasized hatcheries’ social, economic, cultural, and ecological benefits, Skeptics and Restorers prioritized minimizing ecological harm and questioned hatchery effectiveness. Balancers acknowledged both social benefits and ecological risks, supporting context-specific management. All groups articulated different meanings of the term “wild,” suggesting that different perspectives across typologies may exacerbate fundamental miscommunications. Conclusion: Our findings highlight the complexity of stakeholder views and the limitations of binary framings. We suggest that tailored communication and engagement strategies, informed by typologies, may foster more inclusive and productive dialogue in hatchery policy and management.

Oregon↗
USGS2026

Region-specific understanding of virus transmission to support salmonid health at hatcheries in three regions of the Pacific Northwest, North America

Juvenile salmonid mortality due to infectious haematopoietic necrosis virus (IHNV) can be a major burden on fish hatcheries. We consider possible IHNV transmission routes and specialist–generalist patterns across three regions in the Pacific Northwest of North America: Coastal Washington and Oregon (CWO), Lower Columbia River Basin (LCRB) and Snake River Basin (SRB) to obtain multi-region inference about IHNV transmission and specialization. While individual regions have been studied previously, our consideration of three regions to identify consistent trends or localized patterns is novel. The most consistent patterns we found were that most exposure to IHNV was from migrating adult salmonids and that the IHNV lineage MD specialized in steelhead and rainbow trout. Our results were consistent with LCRB being a source of IHNV and the SRB and CWO being sinks. Results specific to particular regions include the role of local geography on exposure and influence of hatchery complexes on transmission, which highlights the need to understand local hatchery operations before disease ecology can be understood and suitable hatchery management can be planned. Results demonstrate the need for spatially and temporally explicit quantitative approaches to understand disease dynamics and inform management.

Oregon, Washington↗
USGS2026

Epigenetics in captivity: Restoring wild phenotypes in captive-reared salmonids

Captive rearing is a common practice for the stocking, conservation, and supplementation of fish species worldwide, but captive-reared fish can exhibit altered phenotypes leading to reduced fitness in nature compared to wild conspecifics. In salmonids, certain studies have found limited genetic differentiation between wild and captive-reared fish. However, documented changes in gene expression in hatchery fish have led scientists to investigate epigenetic mechanisms, such as DNA methylation, as a source of these differences. In this binational collaborative piece, we synthesize the knowledge and efforts of academics and government scientists to highlight how interactions between captive rearing and the epigenome elicit parallel phenotypic changes across salmonid species. We examine the known and potential links between DNA methylation and the phenotypic effects of captive rearing including changes in behavior, color, gut microbiomes, and developmental abnormalities. We review efforts to minimize these phenotypic and epigenetic effects including attempts to modify the hatchery environment and rearing protocols. We provide a framework to integrate epigenetic considerations into hatchery rearing protocols by weighing the heritable nature of DNA methylation with the goals of different captive rearing programs and explore whether minimizing the phenotypic and epigenetic effects of captive rearing is worthwhile. We examine heritability and persistence of epigenetic effects, and we propose the exploitation of heritable bet-hedging as an epigenetic buffer to increase post-release survival. We also suggest novel applications of epigenomic biomarkers as a non-lethal method for post-release monitoring. Ultimately, collaborative multi-disciplinary research across species is needed to understand the comprehensive effects of captive rearing, reduce the ecological impacts of captive fish in the wild, and increase population resilience. Integrating epigenetics into fish hatchery management will provide new opportunities for optimizing and improving captive rearing.

Evolutionary Applications↗
USGS2016

Islands in the ice stream: were spawning habitats for native salmonids in the Great Lakes created by paleo-ice streams?

Lake trout Salvelinus namaycush , lake whitefish Coregonus clupeaformis and cisco Coregonus artedi are salmonid fishes native to the Laurentian Great Lakes that spawn on rocky substrates in the fall and early winter. After comparing the locations of spawning habitat for these species in the main basin of Lake Huron with surficial substrates and the hypothesized locations of fast-flowing Late Wisconsinan paleo-ice streams, we hypothesize that much of the spawning habitat for these species in Lake Huron is the result of deposition and erosion by paleo-ice streams. This hypothesis may represent a new framework for the identification and protection of spawning habitat for these native species, some of which are currently rare or extirpated in some of the Great Lakes. We further suggest that paleo-ice streams may have been responsible for the creation of native salmonid spawning habitat elsewhere in the Great Lakes and in other glaciated landscapes.

Lake Huron↗
USGS2025

Effects of riparian forest thinning on resident salmonid fishes in coastal northern California catchments

Resource managers are interested in whether thinning second-growth forests may be a viable restoration strategy for stream and riparian habitats, but may be concerned about the potential impacts that increases in stream temperature associated with riparian thinning treatments may have on cold-water salmonid fishes. We evaluated the effects of riparian forest thinning on resident populations of coastal cutthroat trout ( Oncorhynchus clarkii clarkii ) in coastal northern California catchments using a manipulative field experiment with a replicated before-after-control-impact design (pre-treatment data collected in 2016, thinning treatments occurred in 2017, and post-treatment data collected in 2018). Experimental thinning treatments reduced riparian shade by 20%–30% along five 150–200 m stream reaches. To provide a process-based evaluation of the implications of riparian thinning for coastal cutthroat trout, we combined seasonal observations of trout density, biomass, and growth with bioenergetics modelling. Cutthroat trout density increased by 8%–31% and biomass increased by 27%–111% in thinned reaches 1 year post-treatment, but responses varied widely across sites and seasons so did not always differ statistically. Growth rates of cutthroat trout varied more among seasons than among reach types (upstream reference, thinned, and downstream), peaking in spring and overwinter relative to summer. Bioenergetics modelling indicated that cutthroat trout responded to thinning-induced increases in stream temperature and shifts in prey energy density via higher consumption rates (i.e., fish fed more frequently) in thinned reaches. Additionally, reach-scale consumption estimates indicated that the energy intake of cutthroat trout increased at the population level in thinned reaches. However, thinned reaches exhibited relatively small changes in consumption, suggesting that riparian thinning was unlikely to enhance growth opportunities for cutthroat trout, supporting our empirical growth observations. Collectively, our field experiment suggests that salmonid fishes may be resilient to thinning second-growth riparian forests when treatments do not substantially increase water temperatures. Moreover, our results highlight that pairing empirical data with bioenergetics modelling can provide valuable insights into the mechanisms driving fish responses to riparian forest restoration.

California↗
USGS2023

Shrinking body size and climate warming: Many freshwater salmonids do not follow the rule

Declining body size is believed to be a universal response to climate warming and has been documented in numerous studies of marine and anadromous fishes. The Salmonidae are a family of coldwater fishes considered to be among the most sensitive species to climate warming; however, whether the shrinking body size response holds true for freshwater salmonids has yet to be examined at a broad spatial scale. We compiled observations of individual fish lengths from long-term surveys across the Northern Hemisphere for 12 species of freshwater salmonids and used linear mixed models to test for spatial and temporal trends in body size (fish length) spanning recent decades. Contrary to expectations, we found a significant increase in length overall but with high variability in trends among populations and species. More than two-thirds of the populations we examined increased in length over time. Secondary regressions revealed larger-bodied populations are experiencing greater increases in length than smaller-bodied populations. Mean water temperature was weakly predictive of changes in body length but overall minimal influences of environmental variables suggest that it is difficult to predict an organism's response to changing temperatures by solely looking at climatic factors. Our results suggest that declining body size is not universal, and the response of fishes to climate change may be largely influenced by local factors. It is important to know that we cannot assume the effects of climate change are predictable and negative at a large spatial scale.

Global Change Biology↗
USGS2014

Interspecific habitat associations of juvenile salmonids in Lake Ontario tributaries: implications for Atlantic salmon restoration

Diel variation in habitat use of subyearling Chinook salmon ( Oncorhynchus tshawytscha ), subyearling coho salmon ( O. kisutch ), yearling steelhead ( O. mykiss ), and yearling Atlantic salmon ( Salmo salar ) was examined during the spring in two tributaries of Lake Ontario. A total of 1318 habitat observations were made on juvenile salmonids including 367 on steelhead, 351 on Chinook salmon, 333 on Atlantic salmon, and 261 on coho salmon. Steelhead exhibited the most diel variation in habitat use and Chinook the least. Juvenile salmonids were generally associated with more cover and larger substrate during the day in both streams. Interspecific differences in habitat use in both streams occurred with Atlantic salmon (fast velocities) and coho salmon (pools) using the least similar habitat. Chinook salmon and Atlantic salmon used similar habitat in both streams. These findings should help guide future management actions specific to habitat protection and restoration of Atlantic salmon in Lake Ontario tributaries.

New York↗
USGS2023

Timing of reproduction underlies fitness tradeoffs for a salmonid fish

Life history diversity is generated and maintained in part by density-dependent fitness tradeoffs that inhibit a single trait value from reaching fixation. While central to our understanding of evolution, demonstrating density dependence in the strength of fitness tradeoffs is difficult in natural systems. The timing of reproduction is a key life history trait that determines access to breeding habitat and exposure of offspring to competitive interactions and environmental conditions. Understanding the processes underlying diversity in reproductive timing will aid efforts to increase adaptive capacity under global environmental change. Here, we used detailed field studies, genetic parentage assignment, and simulation modeling to evaluate the fitness tradeoffs associated with the timing of reproduction for Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri in groundwater-dominated tributaries to the upper Snake River, Wyoming, USA. We conducted our study across two years to understand how the strength of tradeoffs changes with population density. We found that early breeders experienced reduced reproductive success relative to later breeders due to the negative impact of nest superimposition (where later breeders construct nests overlapping those constructed previously) on embryo survival. However, as the risk of superimposition declined in the low-density year and early breeders experienced fewer losses, reproductive success became more similar among individuals breeding at different times. Further, in the spring following the critical period for growth and survival, offspring of early breeders had experienced longer growing seasons, attained larger body sizes, and were equally abundant relative to those of later breeders, suggesting that fitness losses due to superimposition may be offset by size-dependent competitive ability and overwinter survival. Our results illustrate a mechanism underlying diversity in the timing of reproduction for salmonids. This type of life history diversity will help to ensure the resilience and stability of salmonid populations attempting to adapt to changing local stressors associated with global climate change.

Oikos↗
USGS2018

Effects of land use on summer thermal regimes in critical salmonid habitats of the Pacific Northwest

The effect of climate change on stream temperature regimes is of significant concern to natural resource managers focused on protecting cold-water-dependent species. Nevertheless, understanding of how human land-use activities may act to exacerbate the effects of climate change on stream temperature regimes is limited. Using extensive stream temperature data with high-resolution climate and habitat data, we quantified how land management activities are related to summer stream temperatures across the Pacific Northwest, USA. We then described the distribution of land management practices influencing summer thermal regimes relative to the distribution of salmonid fish species of conservation concern. After accounting for climatic and geophysical variation, we detected a strong relationship between livestock grazing and summer thermal regimes. Maximum, average, and diel variation in water temperature was greater where livestock grazing was present. Livestock grazing was widespread, occurring in 43%–100% of sites supporting salmonid species of conservation concern. Thus, current land management practices may be intensifying the effects of ongoing climate change in freshwater habitats, acting to further threaten cold-water fishes of conservation concern.

Washington, Oregon, Idaho, Montana↗
USGS2023

Who spawns where? Temperature, elevation, and discharge differentially affect the distribution of breeding by six Pacific salmonids within a large river basin

Within the geographic range of salmonid fishes, many apparently suitable rivers and streams are used for reproduction by some species but not others. This is widely known but seldom addressed, as studies often examine factors determining the distribution of one or only a few species. We examined physical factors associated with the spawning distribution of six native Pacific salmonids (pink, chum, coho, and Chinook salmon, bull trout, and steelhead) in the Skagit River basin, Washington. Annual mean temperature and catchment elevation had the strongest association with spawning assemblage distribution, but stream length, annual discharge, seasonal hydrology, and land use were also influential. Some species (e.g., pink and Chinook salmon) were more closely associated with each other and with common variables than others, and bull trout were the most distinctive. For interpretation, we investigated the roles of adult body size, timing of spawning, and duration of juvenile rearing, but none of these factors explained groupings in the data. Interspecific differences in habitat association remained, suggesting fundamental constraints on species distributions with implications for conservation and restoration.

Washington↗