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opencc-zeroDec 2013View details →

Data from: Divergent immunity and energetic programs in the gills of migratory and resident Oncorhynchus mykiss

Divergent life history strategies occur in steelhead or rainbow trout Oncorhynchus mykiss, and many populations produce both migrant (anadromous fish that move to the ocean after rearing) and resident (do not migrate and remain in fresh water) individuals. Mechanisms leading to each type are only partially understood; while the general tendency of a population is heritable, individual tendency may be plastic, influenced by local environment. Steelhead hatchery programmes aim to mitigate losses in wild stocks by producing trout that will migrate to the ocean and not compete with wild trout for limited freshwater resources. To increase our understanding of gill function in these migratory or resident phenotypes, here we compare gill transcriptome profiles of hatchery-released fish either at the release site (residents) or five river kilometres downstream while still in full fresh water (migrants). To test whether any of these genes can be used as predictive markers for smoltification, we compared these genes between migrant-like and undifferentiated trout while still in the hatchery in a common environment (prerelease). Results confirmed the gradual process of smoltification, and the importance of energetics, gill remodelling and ion transport capacity for migrants. Additionally, residents overexpressed transcripts involved in antiviral defences, potentially for immune surveillance via dendritic cells in the gills. The best smoltification marker candidate was protein s100a4, expression of which was highly correlated with Na(+) , K(+) ATPase (NKA) activity and smolt-like morphology in pre- and postrelease trout gills.

opencc-zeroDec 2017View details →

Data from: Increased natural reproduction and genetic diversity one generation after cessation of a steelhead trout (Oncorhynchus mykiss) conservation hatchery program

Spatial and temporal fluctuations in productivity and abundance confound assessments of captive propagation programs aimed at recovery of Threatened and Endangered populations. We conducted a 17 year before-after-control-impact experiment to determine the effects of a conservation hatchery program for anadromous steelhead trout (Oncorhynchus mykiss) on a key indicator of natural reproduction (naturally produced nests or 'redds'). The supplemented population exhibited a significant (2.6-fold) increase in redd abundance in the generation following supplementation. Four non-supplemented (control) populations monitored over the same 17 year period exhibited stable or decreasing trends in redd abundance. Expected heterozygosity in the supplemented population increased significantly. Allelic richness increased, but to a lesser (non-significant) degree. Estimates of the effective number of breeders increased from a harmonic mean of 24.4 in the generation before supplementation to 38.9 after supplementation. Several non-conventional aspects of the captive rearing program may have contributed to the positive response in the natural population.

opencc-zeroMay 2020View details →

Data from: Step-patterned survivorship curves: mortality and loss of equilibrium responses to high temperature and food restriction in juvenile rainbow trout (Oncorhynchus mykiss)

While survivorship curves typically exhibit smooth declines over time, step-patterned curves can occur with multiple stressors within a life stage. To explore this process, we examined the effects of heat (24 ºC) and food restriction on juvenile rainbow trout (Oncorhynchus mykiss Walbaum) in challenge experiments. We observed step-patterned survivorship curves determined by mortality and loss of equilibrium (LOE) endpoints. To examine the cause of heterogeneity in the stress responses from early to late mortality and LOE, we measured indices of energetic reserves. The step transition in the survivorship curves, the peak mortality rates, and start of when individuals reached a critical energetic threshold (14% dry mass; 4.0 kJ·g-1 energy) all occurred at around days 10-15 of the challenge. The coherence in these temporal patterns suggest heterogeneity in the cohort stress responses, in which an early subgroup died from heat stress and a late subgroup died from starvation. Thus, their endpoint sensitivities resulted in step-patterned survivorship curves. We discuss the implications of the study for understanding effects of multiple stressors on population heterogeneity and note the possible significance of stress response selection under climate change in which heat stress and food limitations occur in concert.

opencc-zeroDec 2012View details →

Data from: Large-scale parentage analysis reveals reproductive patterns and heritability of spawn timing in a hatchery population of steelhead (Oncorhynchus mykiss)

Understanding life history traits is an important first step in formulating effective conservation and management strategies. The use of artificial propagation and supplementation as such a strategy can have numerous effects on the supplemented natural populations and minimizing life history divergence is crucial in minimizing these effects. Here, we use single nucleotide polymorphism (SNP) genotypes for large-scale parentage analysis and pedigree reconstruction in a hatchery population of steelhead, the anadromous form of rainbow trout. Nearly complete sampling of the broodstock for several consecutive years in two hatchery programmes allowed inference about multiple aspects of life history. Reconstruction of cohort age distribution revealed a strong component of fish that spawn at 2 years of age, in contrast to programme goals and distinct from naturally spawning steelhead in the region, which raises a significant conservation concern. The first estimates of variance in family size for steelhead in this region can be used to calculate effective population size and probabilities of inbreeding, and estimation of iteroparity rate indicates that it is reduced by hatchery production. Finally, correlations between family members in the day of spawning revealed for the first time a strongly heritable component to this important life history trait in steelhead and demonstrated the potential for selection to alter life history traits rapidly in response to changes in environmental conditions. Taken together, these results demonstrate the extraordinary promise of SNP-based pedigree reconstruction for providing biological inference in high-fecundity organisms that is not easily achievable with traditional physical tags.

opencc-zeroDec 2016View details →

Data from: Contrasting genetic metrics and patterns among naturalized rainbow trout (Oncorhynchus mykiss) in two Patagonian lakes differentially impacted by trout aquaculture

Different pathways of propagation and dispersal of non-native species into new environments may have contrasting demographic and genetic impacts on established populations. Repeated introductions of rainbow trout (Oncorhynchus mykiss) to Chile in South America, initially through stocking and later through aquaculture escapes, provide a unique setting to contrast these two pathways. Using a panel of single nucleotide polymorphisms, we found contrasting genetic metrics and patterns among naturalized trout in Lake Llanquihue, Chile's largest producer of salmonid smolts for nearly 50 years, and Lake Todos Los Santos (TLS), a reference lake where aquaculture has been prohibited by law. Trout from Lake Llanquihue showed higher genetic diversity, weaker genetic structure and larger estimates for the effective number of breeders (Nb) than trout from Lake TLS. Trout from Lake TLS were divergent from Lake Llanquihue, and showed marked genetic structure and a significant isolation-by-distance pattern consistent with secondary contact between documented and undocumented stocking events in opposite shores of the lake. Multiple factors, including differences in propagule pressure, origin of donor populations, lake geomorphology, and habitat quality or quantity, may concomitantly explain contrasting genetic metrics and patterns for trout between lakes. We also discussed violations of assumptions that may lead to overestimating Nb . We contend that high propagule pressure from aquaculture may not only increase genetic diversity and Nb via demographic effects and admixture, but also may impact the evolution of genetic structure and increase gene flow, consistent with findings from artificially propagated salmonid populations in their native and naturalized ranges.

opencc-zeroDec 2016View details →

Data from: Restricted gene flow between resident Oncorhynchus mykiss and an admixed population of anadromous steelhead

The species Oncorhynchus mykiss is characterized by a complex life history that presents a significant challenge for population monitoring and conservation management. Many factors contribute to genetic variation in O. mykiss populations, including sympatry among migratory phenotypes, habitat heterogeneity, hatchery introgression, and immigration (stray) rates. The relative influences of these and other factors are contingent on characteristics of the local environment. The Rock Creek subbasin in the middle Columbia River has no history of hatchery supplementation and no dams or artificial barriers. Limited intervention and minimal management have led to a dearth of information regarding the genetic distinctiveness of the extant O. mykiss population in Rock Creek and its tributaries. We used 192 SNP markers and collections sampled over a 5-year period to evaluate the temporal and spatial genetic structures of O. mykiss between upper and lower watersheds of the Rock Creek subbasin. We investigated potential limits to gene flow within the lower watershed where the stream is fragmented by seasonally dry stretches of streambed, and between upper and lower watershed regions. We found minor genetic differentiation within the lower watershed occupied by anadromous steelhead (FST = 0.004), and evidence that immigrant influences were prevalent and ubiquitous. Populations in the upper watershed above partial natural barriers were highly distinct (FST = 0.093) and minimally impacted by apparent introgression. Genetic structure between watersheds paralleled differences in local demographics (e.g., variation in size), migratory restrictions, and habitat discontinuity. The evidence of restricted gene flow between putative remnant resident populations in the upper watershed and the admixed anadromous population in the lower watershed has implications for local steelhead productivity and regional conservation.

opencc-zeroDec 2021View details →

It takes time to heal a broken heart: Ventricular plasticity improves heart performance after myocardial infarction in rainbow trout, Oncorhynchus mykiss

Coronary arteriosclerosis is a common feature of both wild and farmed salmonid fishes and may be linked to stress-induced cardiac pathologies. Yet, the plasticity and capacity for long-term myocardial restructuring and recovery following a restriction in coronary blood supply is unknown. Here, we analyzed the consequences of acute (3 days) and chronic (from 33 to 62 days) coronary occlusion (i.e., coronary artery ligation) on cardiac morphological characteristics and in vivo function in juvenile rainbow trout, Oncorhynchus mykiss. Acute coronary occlusion resulted in elevated resting heart rate and decreased inter-beat variability, which are both markers of autonomic dysfunction following acute myocardial ischemia, along with severely reduced heart rate scope (maximum – resting heart rate) relative to sham-operated trout. We also observed a loss of myocardial interstitial collagen and compact myocardium. Following long-term coronary- ligation, resting heart rate and heart rate scope normalized relative to sham-operated trout. Moreover, a distinct fibrous collagen layer separating the compact myocardium into two layers had formed. This may contribute to maintain ventricular integrity across the cardiac cycle, or alternatively, demark a region of the compact myocardium that continues to receive oxygen from the luminal venous blood. Taken together, we demonstrate that rainbow trout may cope with the aversive effects caused by coronary artery obstruction through plastic ventricular remodeling, which, at least in part, restores cardiac performance and myocardium oxygenation.

opencc-zeroFeb 2022View details →

Assessing the population genetic structure of introduced rainbow trout (Oncorhynchus mykiss) in the Lake Tahoe basin: A case for understanding hybridization potential during the reintroduction of the native Endangered Species Act listed Lahontan cutthroat trout (O. clarkii henshawi)

Hybridization with introduced or invasive species is a major threat and driver of population declines in native salmonids. The rainbow trout (Oncorhynchus mykiss, RBT) has been widely introduced globally and represents an important invasive species, often establishing entrenched naturalized populations. The cutthroat trout (Oncorhynchus clarkii, CT), a close congener, is particularly susceptible to competition and hybridization from RBT introductions which has led to range-wide population declines and loss of CT genetic variation. The Lahontan CT (O. c. henshawi, LCT) whose historic distribution included the Lake Tahoe basin, was extirpated by the 1940s due to overfishing and introduction of nonnative salmonids, including now naturalized RBT. Here, we characterize genetic variation of RBT in a subset of Lake Tahoe tributaries to assess potential homing of RBT to streams for spawning, thereby informing LCT reintroduction. Diploid reproductively viable RBT were stocked annually into Lake Tahoe from the late 1800s until the mid-2000s by California and Nevada fish and wildlife agencies, planting the same commonly raised hatchery strains over time. Since 2007, triploid RBT comprise the bulk of RBT planted. Despite extensive dispersal from stocking locations, our analyses revealed variation in population differentiation among tributaries, with individuals from spatially proximate streams clustering across multiple population genetic analyses. Although subtle, we detected evidence for genetic differentiation among tributaries from the southern, western, and northern regions, including surprising structure involving a single tributary. These results illustrate the extent of differentiation within and among streams and could inform possibilities for and implications of RBT removal and LCT reintroduction.

opencc-zeroDec 2015View details →

Data from: Broodstock history strongly influences natural spawning success in hatchery steelhead (Oncorhynchus mykiss)

We used genetic parentage analysis of 6200 potential parents and 5497 juvenile offspring to evaluate the relative reproductive success of hatchery and natural steelhead (Onchorhynchus mykiss) when spawning in the wild between 2008 and 2011 in the Wenatchee River, Washington. Hatchery fish originating from two prior generation hatchery parents had <20% of the reproductive success of natural origin spawners. In contrast, hatchery females originating from a cross between two natural origin parents of the prior generation had equivalent or better reproductive success than natural origin females. Males originating from such a cross had reproductive success of 26–93% that of natural males. The reproductive success of hatchery females and males from crosses consisting of one natural origin fish and one hatchery origin fish was 24–54% that of natural fish. The strong influence of hatchery broodstock origin on reproductive success confirms similar results from a previous study of a different population of the same species and suggests a genetic basis for the low reproductive success of hatchery steelhead, although environmental factors cannot be entirely ruled out. In addition to broodstock origin, fish size, return time, age, and spawning location were significant predictors of reproductive success. Our results indicate that incorporating natural fish into hatchery broodstock is clearly beneficial for improving subsequent natural spawning success, even in a population that has a decades-long history of hatchery releases, as is the case in the Wenatchee River.

FIGURE 7 in Molecular Systematics of Redband Trout from Genome-Wide DNA Sequencing Substantiates the Description of a New Taxon (Salmonidae: Oncorhynchus mykiss calisulat) from the McCloud River

FIGURE 7. Phylogenetic network of individuals examined in this study produced by the neighbor net algorithm. Tips are labeled by individual codes described in Table 1. Each subspecies of Rainbow Trout (Oncorhynchus mykiss) is indicated. McCloud River Redband Trout (O. m. calisulat, ssp. nov.) and Sacramento River Redband Trout (O. m. stonei) are show in bold. The outgroup species, Lahontan Cutthroat Trout (O. clarkii henshawi) is indicated.

FIGURE 3 in Molecular Systematics of Redband Trout from Genome-Wide DNA Sequencing Substantiates the Description of a New Taxon (Salmonidae: Oncorhynchus mykiss calisulat) from the McCloud River

FIGURE 3. Admixture plots from the population genetics data set. Number of genetic clusters (K) presented for K = 2–6 from all samples (n = 318) analyzed in a population genetics framework. Admixture analysis was conducted in NGSAdmix with an optimal K = 3. Labeling of x-axis is according to Group as in Table 1: CAGT, California Golden Trout; KRRT, Kern River Rainbow Trout; LKGT, Little Kern Golden Trout; CRT, Coastal Rainbow Trout; EGLK, Eagle Lake Rainbow Trout; HRNB, Hatchery Rainbow Trout; MRRB, McCloud River Redband Trout; REDB, all other Redband Trout.

FIGURE 6 in Molecular Systematics of Redband Trout from Genome-Wide DNA Sequencing Substantiates the Description of a New Taxon (Salmonidae: Oncorhynchus mykiss calisulat) from the McCloud River

FIGURE 6. Species tree produced by SVDQuartets. The species tree branch lengths are equal and bootstrap support was maximal for all nodes and not shown. Each subspecies of Rainbow Trout (Oncorhynchus mykiss) is indicated with McCloud River Redband Trout (O. m. calisulat, ssp. nov.) and Sacramento Redband Trout (O. m. stonei) in bold text. For Rainbow Trout subspecies, sampling locations are labeled with a four-letter code corresponding to Figure 1 and Table 1. The two samples of Lahontan Cutthroat Trout (O. clarkii henshawi) are labeled as LCT.

FIGURE 2 in Molecular Systematics of Redband Trout from Genome-Wide DNA Sequencing Substantiates the Description of a New Taxon (Salmonidae: Oncorhynchus mykiss calisulat) from the McCloud River

FIGURE 2. Principal Component Analyses. The first two Principal Components (PCs) are presented for all samples (n = 318) in the population genetics analysis in A and Redband Trout samples (n = 204) in B. Genotype likelihoods were generated separately for the PCs presented in each panel. In A points are color coded by Group corresponding broadly to lineage, and further condensed into a Major Group by consolidating the California Golden Trout Complex and represented by shape (Table 1). In B, points are colored by watershed and the same shape applied to the Major Group (MRRB and REDB). Abbreviations for Major Group are explained in the text.

FIGURE 1 in Molecular Systematics of Redband Trout from Genome-Wide DNA Sequencing Substantiates the Description of a New Taxon (Salmonidae: Oncorhynchus mykiss calisulat) from the McCloud River

FIGURE 1. Map of key features and distributions of key lineages in this study. The distribution of Coastal Rainbow Trout (Oncorhynchus mykiss irideus) is shown in grey shading. Other lineages are labeled in different colors. Distributions were retrieved from the PISCES database (pisces.ucdavis.edu, "Historic Range—Expert Opinion") except for Warner Lakes Redband Trout (O. m. ssp.), which is represented by a polygon of hydrologic unit code (HUC) 17120007. Sampling locations used in phylogenetic analyses are indicated with a four-letter code that corresponds to Table 1 and Supplemental Table S1. Samples of O. m. gairdnerii from Idaho are not shown.

FIGURE 5 in Molecular Systematics of Redband Trout from Genome-Wide DNA Sequencing Substantiates the Description of a New Taxon (Salmonidae: Oncorhynchus mykiss calisulat) from the McCloud River

FIGURE 5. Maximum Likelihood (ML) tree (A) and ML consensus tree (B). In both panels subspecies of Rainbow Trout (Oncorhynchus mykiss) are indicated along with members of the Golden Trout Complex. McCloud River Redband Trout (O. m. calisulat, ssp. nov.) and Sacramento Redband Trout (O. m. stonei) are indicated with bold text. Individual sample names are provided at tips and further described in Table 1. In 5A, nodes receiving Shimodaira-Hasegawa approximate Likelihood Ratio Test scores> 80 and bootstrap support (BS)> 95% are indicated with a diamond. In 5B, two spans of bootstrap support are presented, with 100%> BS> 95% as solid black circles and 95%> BS> 90% as grey circles at nodes.

FIGURE 8 in Molecular Systematics of Redband Trout from Genome-Wide DNA Sequencing Substantiates the Description of a New Taxon (Salmonidae: Oncorhynchus mykiss calisulat) from the McCloud River

FIGURE 8. McCloud River Redband Trout, Onchorhynchus mykiss calisulat, ssp. nov., Sheepheaven Creek. A. WFB 5020, holotype, 120 mm SL. B. same specimen as in A, radiograph. C. TCWC 28772.01, paratype, 144 mm SL. D. Illustration of O. m. calisulat, ssp. nov., showing life colors, © J. Tomelleri, used with permission.

FIGURE 4 in Molecular Systematics of Redband Trout from Genome-Wide DNA Sequencing Substantiates the Description of a New Taxon (Salmonidae: Oncorhynchus mykiss calisulat) from the McCloud River

FIGURE 4. Admixture plots from McCloud river trout and other Redband Trout in population genetics dataset. Admixture results from NGSAdmix for genetic clusters (K) from 2-4 with the subset of samples collected as Redband Trout. Sample size of 204, optimal K = 2. The x-axis labels are labeled according to watershed.