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At least 469 records · Page 26Linked to original sources
USGS2024

Genome-wide association analysis of the resistance to infectious hematopoietic necrosis virus in two rainbow trout aquaculture lines confirms oligogenic architecture with several moderate effect quantitative trait loci

Infectious hematopoietic necrosis (IHN) is a disease of salmonid fish that is caused by the IHN virus (IHNV), which can cause substantial mortality and economic losses in rainbow trout aquaculture and fisheries enhancement hatchery programs. In a previous study on a commercial rainbow trout breeding line that has undergone selection, we found that genetic resistance to IHNV is controlled by the oligogenic inheritance of several moderate and many small effect quantitative trait loci (QTL). Here we used genome wide association analyses in two different commercial aquaculture lines that were naïve to previous exposure to IHNV to determine whether QTL were shared across lines, and to investigate whether there were major effect loci that were still segregating in the naïve lines. A total of 1,859 and 1,768 offspring from two commercial aquaculture strains were phenotyped for resistance to IHNV and genotyped with the rainbow trout Axiom 57K SNP array. Moderate heritability values (0.15–0.25) were estimated. Two statistical methods were used for genome wide association analyses in the two populations. No major QTL were detected despite the naïve status of the two lines. Further, our analyses confirmed an oligogenic architecture for genetic resistance to IHNV in rainbow trout. Overall, 17 QTL with notable effect (≥1.9% of the additive genetic variance) were detected in at least one of the two rainbow trout lines with at least one of the two statistical methods. Five of those QTL were mapped to overlapping or adjacent chromosomal regions in both lines, suggesting that some loci may be shared across commercial lines. Although some of the loci detected in this GWAS merit further investigation to better understand the biological basis of IHNV disease resistance across populations, the overall genetic architecture of IHNV resistance in the two rainbow trout lines suggests that genomic selection may be a more effective strategy for genetic improvement in this trait.

Frontiers in Genetics↗
USGS2021

Evaluating coexistence of fish species with coastal cutthroat trout in low order streams of western Oregon and Washington, USA

When multiple species of fish coexist there are a host of potential ways through which they may interact, yet there is often a strong focus on studies of single species without considering these interactions. For example, many studies of forestry–stream interactions in the Pacific Northwest have focused solely on the most prevalent species: Coastal cutthroat trout. To examine the potential for interactions of other fishes with coastal cutthroat trout, we conducted an analysis of 281 sites in low order streams located on Washington’s Olympic Peninsula and along the central Oregon coast. Coastal cutthroat trout and juvenile coho salmon were the most commonly found salmonid species within these streams and exhibited positive associations with each other for both presence and density. Steelhead were negatively associated with the presence of coastal cutthroat trout as well as with coho salmon and sculpins (Cottidae). Coastal cutthroat trout most frequently shared streams with juvenile coho salmon. For densities of these co-occurring species, associations between these two species were relatively weak compared to the strong influences of physical stream conditions (size and gradient), suggesting that physical conditions may have more of an influence on density than species interactions. Collectively, our analysis, along with a review of findings from prior field and laboratory studies, suggests that the net effect of interactions between coastal cutthroat trout and coho salmon do not appear to inhibit their presence or densities in small streams along the Pacific Northwest.

Washington↗
USGS2022

Individual characteristics and abiotic factors influence out-migration dynamics of juvenile bull trout

Fragmentation of rivers through anthropogenic modifications poses an imminent threat to the persistence of migratory fish, necessitating direct actions such as trap-and-haul programs to restore and conserve the migratory life-history component in populations of partially migratory species such as bull trout Salvelinus confluentus. We used a PIT-tag system to assess how biological and abiotic factors influence the out-migration dynamics of juvenile bull trout in Graves Creek, Montana, USA. The largest fish within a cohort were more likely to out-migrate at age 1 when compared to smaller fish within the cohort, and this was particularly evident in a high-density year-class (2018), where large bull trout out-migrated an average of 115 days earlier than bull trout in the medium size category, and 181 days earlier than bull trout in the small size category. Relative changes in abiotic factors, including discharge, water temperature, and photoperiod, appeared to act as cues to out-migration, with the direction of change varying by season. These results highlight the complex interplay between individual characteristics, population dynamics, and environmental conditions, which influence out-migration dynamics and can be used to inform management actions to conserve the migratory component in bull trout populations.

Idaho, Montana↗
USGS1979

Membrane immunoglobulin is present on thymic and splenic lymphocytes of the trout Salmo gairdneri

Three rabbit antisera raised to trout IgM showed positive immunofluorescent reactions with lymphocytes of trout spleen and thymus. These antisera showed no detectable cross-reactivity with keyhole limpet hemocyanin, as determined by direct radioimmune precipitation and adsorption, and did not appeare to react significantly with carbohydrate moieties on trout IgM, as determined by the failure of proteolytic digests of trout IgM to inhibit in radioimmunoassay against intact trout IgM. Membrane immunoglobulin determinants were detectable on the membrane of both thymocytes and splenocytes with the lactoperoxidase-catalyzed iodination reaction. Radioimmunoassay of lysates of lymphocytes confirmed the association of immunoglobulin with trout thymocytes. By radioimmunoassay, lysates of thymic and splenic lymphocytes contained similar amounts of immunoglobulin, equivalent to approximately 8 × 10 4 molecules of IgM per cell (calculated as the monomer µ 2 L 2 ).

Journal of Immunology↗
USGS2004

Spawning ecology of finespotted Snake River cutthroat trout in spring streams of the Salt River valley, Wyoming

We studied spawning ecology of cutthroat trout (Oncorhynchus clarki) in streams that originate as springs along the Salt River, a Snake River tributary in western Wyoming. We assessed (1) relative numbers of upstream-migrant and resident adults present during the spawning period in spring streams, (2) influence of habitat modification on use of spring streams for spawning, and (3) habitat features used for spawning in spring streams. Four spring streams were studied, 2 with substantial modification to enhance trout habitat and 2 with little or no modification. Modifications consisted primarily of constructing alternating pools and gravel-cobble riffles. Only a small portion of adult fish in spring streams during the spawning period had migrated upstream from the Salt River between March and the middle of June. Larger numbers of adult fish and more redds were observed in the 2 modified streams compared with the 2 streams with little or no modification. Most spawning occurred on constructed riffles with small gravel and over a narrow range of depths and velocities. Cutthroat trout, rainbow trout (Oncorhynchus mykiss), and their hybrids were observed in 1 stream with habitat modifications, indicating that measures to halt invasion by rainbow trout, as well as habitat improvement, are needed to preserve this native trout within the Salt River valley.

Western North American Naturalist↗
USGS2005

Fish assemblage structure in an Oklahoma Ozark stream before and after rainbow trout introduction

Rainbow trout Oncorhynchus mykiss have been widely stocked throughout the United States as a popular sport fish. Our study was initiated to evaluate potential effects of rainbow trout introduction on native fishes to inform future decisions about trout stocking in northeastern Oklahoma streams. We sampled fish assemblages in pools, glides, and riffles in Brush Creek, Delaware County, Oklahoma, from February 2000 to September 2002, and experimentally stocked rainbow trout into the stream from November 2000 to March 2001 and November 2001 to March 2002. We used a combination of multivariate analyses to evaluate seasonal and habitat effects on native fish assemblages and to compare assemblage structure between prestocking, the first year of stocking, and the second year of stocking. Mesohabitat type significantly affected assemblage structure among years, whereas we did not detect an effect of season. We did not detect differences in assemblage structure among years in glide or riffle habitats. Native fish assemblage structure in pool habitats before rainbow trout introduction differed from assemblage structure in both the first and second year of stocking. Declines in seven species, including two native game fish (smallmouth bass Micropterus dolomieu and bluegill Lepomis machrochirus), contributed to assemblage dissimilarity in pool habitats between prestocking conditions and the second year of stocking. Our results indicate that stocking rainbow trout may cause local disruption in assemblage structure in pool habitats. ?? 2004 by the American Fisheries Society.

American Fisheries Society Symposium↗
USGS2005

Diet overlap of introduced rainbow trout and three native fishes in an Ozark stream

Private angling groups in Oklahoma have requested permission to stock rainbow trout Oncorhynchus mykiss into streams of northeastern Oklahoma although little is known regarding interactions between introduced rainbow trout and native fishes in these systems. Our study objectives were to assess diet overlap between introduced rainbow trout and native smallmouth bass Micropterus dolomieu, shadow bass Ambloplites ariommus, and bluegill sunfish Lepomis macrochirus in Brush Creek, Oklahoma, a small spring-fed Ozark stream. Rainbow trout diet composition differed from that of all three native fishes in the 2 months of comparison (March and May 2001), and rainbow trout diets contained relatively low numbers of prey. It is unlikely that exploitative competition for food resources occurred between rainbow trout and these three native fishes. ?? 2004 by the American Fisheries Society.

American Fisheries Society Symposium↗
USGS1974

Hydrology and trout populations of cold-water rivers of Michigan and Wisconsin

Statistical multiple-regression analyses showed significant relationships between trout populations and hydrologic parameters. Parameters showing the higher levels of significance were temperature, hardness of water, percentage of gravel bottom, percentage of bottom vegetation, variability of streamflow, and discharge per unit drainage area. Trout populations increase with lower levels of annual maximum water temperatures, with increase in water hardness, and with increase in percentage of gravel and bottom vegetation. Trout populations also increase with decrease in variability of streamflow, and with increase in discharge per unit drainage area. Most hydrologic parameters were significant when evaluated collectively, but no parameter, by itself, showed a high degree of correlation with trout populations in regression analyses that included all the streams sampled. Regression analyses of stream segments that were restricted to certain limits of hardness, temperature, or percentage of gravel bottom showed improvements in correlation. Analyses of trout populations, in pounds per acre and pounds per mile and hydrologic parameters resulted in regression equations from which trout populations could be estimated with standard errors of 89 and 84 per cent, respectively.

Michigan, Wisconsin↗
USGS2016

Mink predation on brown trout in a Black Hills stream

In the early 2000’s, declines in the brown trout (Salmo trutta) fishery in Rapid Creek, South Dakota, caused concern for anglers and fisheries managers. We conducted a radio telemetry study in 2010 and 2011 to identify predation mortality associated with mink, using hatchery-reared (2010) or wild (2011) brown trout. Estimated predation rates by mink (Mustela vison) on radio-tagged brown trout were 30% for hatchery fish and 32% for wild fish. Size frequency analysis revealed that the size distribution of brown trout lost to predation was similar to that of other, radio-tagged brown trout. In both years, a higher proportion of predation mortality (83–92%) occurred during spring, consistent with seasonal fish consumption by mink. Predation by mink appeared to be a significant source of brown trout mortality in our study.

South Dakota↗
USGS2019

Trout as native and non-native species: A management paradox

Native trout are threatened worldwide by introductions of non-native trout that in many cases are themselves threatened within their native range and historical habitats. This chapter focuses on this paradox and addresses how information gained to protect and restore a species in its native range can be used to suppress the same species outside its native range, where it may be invasive. We describe examples of three trout species, Lake Trout, Brown Trout, and Brook Trout, which are managed for the opposing goals of restoration versus suppression, in relation to their opposing roles as both native and non-native species in aquatic communities. We also attempt to develop insights into how this information might be used to accomplish both seemingly incompatible ends.

Book chapter↗
USGS2024

Great Lakes lake trout (Salvelinus namaycush) thiamine monitoring program annual report

Thiamine deficiency in lake trout eggs has been identified to induce early life-stage mortality in the Great Lakes in the 1960s through the 1990s and potentially affecting lake trout recruitment. As a results, the U.S. Geological Survey’s Great Lakes Science Center (GLSC), Eastern Ecological Science Center, and Columbia Environmental Research Center (CERC), and the State University of New York (SUNY) Brockport, in collaboration with partner agencies, have conducted a cooperative program to monitor thiamine concentrations in lake trout Salvelinus namaycush eggs since the late 1990s. In 2023, egg thiamine concentrations were highly variable at each sampling site. No egg samples with thiamine concentrations less than the 4 nmol/g threshold recommended for successful lake trout reproduction were collected in Lakes Superior or Huron. In contrast, 3 to 52% of the lake trout collected at sites in Lakes Michigan, Huron, Ontario and Champlain, and Cayuga Lake had eggs below 4 nmol/g. Time series of mean lake trout egg thiamine concentrations showed high temporal and spatial variability within the Great Lakes region.

Cayuga Lake, Lake Champlain, Lake Erie, Lake Huron↗
USGS2026

Lake Ontario August gillnet survey and lake trout assessment, 2025

Lake Ontario Lake Trout ( Salvelinus namaycush ) rehabilitation has been assessed with fishery dependent and independent surveys to evaluate program benchmarks and compare observations with management objectives since 1983. These surveys provide information on the abundance, strain composition, and performance of stocked Lake Trout, as well as information on levels of natural recruitment, and Sea Lamprey ( Petromyzon marinus ) wounding rates. Lake Trout catch per unit effort (CPUE) in the August gillnet survey was notably lower in 2025. Percentage of naturally produced Lake Trout in US waters continued to be relatively low for mature and immature fish. Sea Lamprey wounding rates on Lake Trout > 432 mm in 2025 were below management target in US waters with zero A1 wounds observed. Overall, the 2025 survey results suggest that Lake Trout indicators continue to meet some of the management objectives but are not showing signs of meaningful recruitment to the adult stock.

Lake Ontario↗
USGS1995

Patterns of egg deposition by lake trout and lake whitefish at Tawas artificial Reef, Lake Huron, 1990-1993

In August 1987, the Michigan Department of Natural Resources (MDNR), with the help and co-sponsorship of Walleyes for Iosco County, constructed Tawas artificial reef to improve recreational fishing in Tawas Bay. Post-construction assessment in October, 1987, by the MDNR found twice as many adult lake trout in a gill net set on the reef as in a similar net set off the reef, indicating that lake trout already had begun to investigate this new habitat. Similar netting efforts in October 1989 caught three times as many adults on the reef as off it, even though the on-reef net was set for less than one third as long a period. Using a remotely operated vehicle (ROV), we detected prespawning aggregations of lake trout on the reef in fall 1989, and MDNR biologists set emergent fly traps on the reef in April-May 1990-1991. These fry traps captured several newly emerged lake trout and lake whitefish fry, demonstrating that eggs of both species has hatched successfully. Gill netting in 1992-1993 by U.S. Fish and Wildlife Service biologists netted large numbers of ripe lake trout in late October and ripe lake whitefish in early to mid-November. The purpose of this paper is to describe the relative quantities of eggs deposited and the spatial patterns of egg deposition by lake trout and lake whitefish at Tawas artificial reef during 1990-1993.

Book chapter↗
USGS2019

Improved detection of rare, endangered and invasive trout using a new large-volume sampling method for eDNA capture

Environmental DNA (eDNA) detection probability increases with volume of water sampled. Common approaches for collecting eDNA samples often require many samples since these approaches usually use fine filters, which restrict the volume of water that can be sampled. An alternative to collecting many, small volume water samples using fine filters may be to collect fewer, large volume water samples using coarse filters that do not clog as rapidly. We used mesocosm experiments and field evaluations to compare coarse filter‐large water volume samples (hereafter large volume filter samples) versus fine filter‐small water volume samples (hereafter small volume filter samples) for detection and quantification of rainbow trout ( Oncorhynchus mykiss ) and bull trout ( Salvelinus confluentus ) DNA. We found that large volume filter sampling can be an effective approach for detecting DNA of low‐density target taxa. In mesocosm experiments, large‐volume and small‐volume water samples detected similar quantities of rainbow trout DNA. In the field, large volume samples more frequently detected bull trout DNA, had higher bull trout DNA copy number, and higher total DNA concentrations than small volume samples. However, sampling higher water volumes increased the potential for PCR inhibition so the DNA workflow had to be altered for large volume samples. Combining larger water volume samples with other strategies, like increasing PCR sensitivity and the number of PCR replicates, will improve detection of rare species, which is crucial for advancing conservation and ecological understanding.

Montana↗
USGS2014

Chronic sensitivity of white sturgeon (Acipenser transmontanus) and rainbow trout (Oncorhynchus mykiss) to cadmium, copper, lead, or zinc in laboratory water-only exposures

Chronic toxicity of cadmium, copper, lead, or zinc to white sturgeon ( Acipenser transmontanus ) and rainbow trout ( Oncorhynchus mykiss ) was evaluated in water-only exposures started with newly hatched larvae or approximately 1-mo-old juveniles. The 20% effect concentration (EC20) for cadmium from the sturgeon tests was higher than the EC20 from the trout tests, whereas the EC20 for copper, lead, or zinc for the sturgeon were lower than those EC20s for the trout. When the EC20s from the present study were included in compiled toxicity databases for all freshwater species, species mean chronic value for white sturgeon was in a relatively low percentile of the species sensitivity distribution for copper (9th percentile) and in the middle percentile for cadmium (55th percentile), zinc (40th percentile), or lead (50th percentile). However, the species mean chronic value for rainbow trout was in a high percentile for copper, lead, and zinc (∼68th–82nd percentile), but in a low percentile for cadmium (23rd percentile). The trout EC20s for each of the 4 metals and the sturgeon EC20s for cadmium or lead were above US Environmental Protection Agency chronic ambient water quality criteria (AWQC) or Washington State chronic water quality standards (WQS), whereas the sturgeon EC20s for copper or zinc were approximately equal to or below the chronic AWQC and WQS. In addition, acute 50% effect concentrations (EC50s) for copper obtained in the first 4 d of the chronic sturgeon test were below the final acute value used to derive acute AWQC and below acute WQS for copper.

Environmental Toxicology and Chemistry↗
USGS1994

Effects of water temperature and pH on toxicity of terbufos, trichlorfon, 4-nitrophenol and 2,4-dinitrophenol to the amphipod Gammarus pseudolimnaeus and rainbow trout (Oncorhynchus mykiss)

Acute toxicity tests were conducted to determine (a) the individual and interactive effects of water temperature (7, 12, 17°C), pH (6 5, 7 5, 8 5, 9 5), and time on the toxicity of terbufos, trichlorfon, 4 nitrophenol, and 2,4-dinitrophenol to rainbow trout ( Oncorhynchus mykiss ) and the amphipod Gammarus pseudohmnaeus , and (b) the individual and interactive effects of water temperature and pH on chemical bioconcentration during acute tests with rainbow trout and Gammarus exposed to terbufos, 4 nitrophenol, and 2,4 dinitrophenol The toxicity of all four chemicals was significantly affected by pH in all tests, except for Gammarus exposed to terbufos The toxicity of terbufos to rainbow trout and Gammarus was less at pH 7 5 than at higher or lower pH The toxicity of both nitrophenols decreased as pH increased, whereas the toxicity of trichlorfon increased with pH The effect of pH on trichlorfon toxicity decreased with temperature Temperature significantly affected the toxicity of all four chemicals to both species Toxicity increased with temperature in all tests, except for rainbow trout exposed to nitrophenols, toxicity decreased as temperature increased for rainbow trout Chemical bioconcentration was also significantly af fected by temperature and pH and was directly related to toxicity in most tests Significant interactive effects between toxicity modifying factors were also frequently observed Temperature and pH effects on chemical toxicity need to be consid ered in chemical hazard assessment to ensure adequate protection of aquatic organisms

Environmental Toxicology and Chemistry↗
USGS2021

Historical data provide important context for understanding declines in Cutthroat Trout

We used historical stocking and population survey records of Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri and other salmonids in the North Fork Shoshone River drainage, Wyoming to summarize fish stocking history and population trends. Based on 98 years of historical records, we found that despite extensive stocking of Yellowstone Cutthroat Trout and minimal stocking of nonnative salmonids after about 1950, populations of wild Yellowstone Cutthroat Trout declined relative to those of nonnative salmonid species. The timing of increases in nonnative salmonids (1970s) did not coincide with their period of most intensive stocking (1935–1950). It is plausible that Yellowstone Cutthroat Trout populations persisted because of high levels of supplemental stocking from 1935 to 1965 and declined with reduced stocking efforts in the 1970s, thereby allowing the increase of introduced nonnative salmonids. The establishment of nonnative salmonids likely further reduced stocking success of Yellowstone Cutthroat Trout due to competition and hybridization. This study demonstrates that an understanding of long-term stocking records and population survey data can be useful for developing and implementing successful management frameworks for the conservation of imperiled fish populations across the United States.

Wyoming↗
USGS2022

Engaging stakeholders to develop a decision support model of conservation risk and management capacity to prioritize investments in Bull Trout recovery

Rarely are sufficient resources available to support the full suite of management actions to promote recovery of a species across their entire distribution. Decision support models are a tool that can inform natural resource management decisions with consideration of the perspectives from a variety of stakeholders who work across large geographic and jurisdictional extents. We offer an example of a decision support model that was developed by several Federal and State natural resource agencies to rank Bull Trout Salvelinus confluentus core areas for prioritizing conservation investment within Oregon, USA. We engaged State level decision makers to identify parameters believed to be influential in determining funding allocations for Bull Trout core areas. Parameters were linked in a model framework that was further refined with input from local Bull Trout experts with knowledge specific to the various core areas. The model produces a relative priority value that is a combination of the conservation risk to the species and the management capacity to address threats. A series of sensitivity analyses suggests that Bull Trout persistence and threat score are most influential in determining the relative priority of a core area, and life-history and genetic diversity are least influential. One of the more powerful products from this work is an interactive web-based application ( https://das.ecosphere.fws.gov/public/obts/ ) that anyone can use to explore how their beliefs in parameter values will affect the relative priority of Bull Trout core areas across Oregon. Our modeling effort is an example of engaging stakeholders with different roles in species recovery and across a large geographic area to create a clearer path forward in allocating limited resources for species recovery. This approach can be employed to address a number of natural resource management situations across species and habitats.

Oregon↗