Assessing the impact of stocking northern-origin hatchery brook trout on the genetics of wild populations in North Carolina

Kazyak, David C.; Rash, Jacob M.; Lubinski, Barbara A.; King, Tim L.

doi:10.1007/s10592-017-1037-4

Cited by 21 publications

(52 citation statements)

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“…However, contemporary molecular data, collected herein, showed little to no signature of genetic hatchery introgression by northern stocks (Kazyak et al. ; D. C. Kazyak, personal observation). The only exception occurred within one sampled stream (Walker Camp Prong), where limited hatchery introgression appeared to have occurred, yet microsatellite genotypes were still largely consistent with those expected of Brook Trout native to the southern Appalachians.…”

Section: Methodsmentioning

confidence: 61%

Neutral Genetic and Phenotypic Variation within and among Isolated Headwater Populations of Brook Trout

et al. 2018

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Isolated populations are challenging to manage and conserve, as they are particularly vulnerable to genetic drift, allelic fixation, and inbreeding and may express markedly reduced phenotypic variability. We sought to improve our understanding of how spatial isolation, occupancy range, and restricted gene flow influence contemporary phenotypic variation within and among native populations of Brook Trout Salvelinus fontinalis by examining the neutral genetic and phenotypic characteristics of 35 isolated headwater populations from Great Smoky Mountains National Park. Across a suite of 13 neutral microsatellite loci, we observed high levels of allelic fixation and considerable genetic differentiation among populations, subwatersheds, and watersheds that were consistent with patterns of isolation. We found significant positive correlations between allelic diversity and estimates of effective population size. In contrast, we observed considerably less phenotypic structure among streams, subwatersheds, and watersheds. Much of the *Corresponding author: tcw5095@psu.edu 1 Retired. 2 Deceased.

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Section: Methodsmentioning

confidence: 61%

Neutral Genetic and Phenotypic Variation within and among Isolated Headwater Populations of Brook Trout

et al. 2018

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“…Negative genetic consequences of stocking on wild populations have been documented in many fish species, particularly in commonly stocked species such as salmonids (Wollebæk et al., ). However, most studies to date that quantify hatchery introgression into wild populations have focused primarily on accidental releases from captive facilities and legacy effects of terminated stocking programs (see Araki & Schmid, for a review, and Kazyak, Rash, Lubinski, & King, for a large‐scale study on brook trout, Salvelinus fontinalis ). Few studies have provided empirical estimates for introgression in populations managed with relatively long‐term (>10 years, in many cases) and recurring stocking events focused on population supplementation (but see Valiquette, Perrier, Thibault, and Bernatchez () and Létourneau et al () for examples of lacustrine lake ( Salvelinus namaycush ) and brook trout populations).…”

Section: Introductionmentioning

confidence: 99%

Limited hatchery introgression into wild brook trout (Salvelinus fontinalis) populations despite reoccurring stocking

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Miller

Dowell

et al. 2018

Evolutionary Applications

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Due to increased anthropogenic pressures on many fish populations, supplementing wild populations with captive‐raised individuals has become an increasingly common management practice. Stocking programs can be controversial due to uncertainty about the long‐term fitness effects of genetic introgression on wild populations. In particular, introgression between hatchery and wild individuals can cause declines in wild population fitness, resiliency, and adaptive potential and contribute to local population extirpation. However, low survival and fitness of captive‐raised individuals can minimize the long‐term genetic consequences of stocking in wild populations, and to date the prevalence of introgression in actively stocked ecosystems has not been rigorously evaluated. We quantified the extent of introgression in 30 populations of wild brook trout (Salvelinus fontinalis) in a Pennsylvania watershed and examined the correlation between introgression and 11 environmental covariates. Genetic assignment tests were used to determine the origin (wild vs. captive‐raised) for 1,742 wild‐caught and 300 hatchery brook trout. To avoid assignment biases, individuals were assigned to two simulated populations that represented the average allele frequencies in wild and hatchery groups. Fish with intermediate probabilities of wild ancestry were classified as introgressed, with threshold values determined through simulation. Even with reoccurring stocking at most sites, over 93% of wild‐caught individuals probabilistically assigned to wild origin, and only 5.6% of wild‐caught fish assigned to introgressed. Models examining environmental drivers of introgression explained <3% of the among‐population variability, and all estimated effects were highly uncertain. This was not surprising given overall low introgression observed in this study. Our results suggest that introgression of hatchery‐derived genotypes can occur at low rates, even in actively stocked ecosystems and across a range of habitats. However, a cautious approach to stocking may still be warranted, as the potential effects of stocking on wild population fitness and the mechanisms limiting introgression are not known.

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“…Geographic locations of 467 collections of wild Brook Trout included in the population genetic baseline. Black points indicate collections that were assessed for hatchery introgression by Kazyak et al (2018). Red stars depict the locations of additional populations used in the present study.…”

Section: Methodsmentioning

confidence: 99%

“…Brook Trout tissue samples were shipped to the U.S. Geological Survey’s Leetown Science Center (Kearneysville, West Virginia), where molecular analyses were conducted. Microsatellite genotypes were obtained for each individual by using the protocols described in Kazyak et al (2018). Briefly, DNA was extracted using the Puregene Kit (Gentra Systems, Minneapolis, Minnesota) or the E‐Z 96 Tissue DNA Kit (Omega Bio‐Tek, Norcross, Georgia).…”

Section: Methodsmentioning

confidence: 99%

“…Anthropogenic alterations to the landscape and introductions of nonnative salmonids (Rainbow Trout Oncorhynchus mykiss and Brown Trout Salmo trutta ) have reduced the range of Brook Trout in the state and throughout its native range (Larson and Moore 1985; Habera and Strange 1993). Intensive stockings of northern‐strain Brook Trout have diminished the genetic integrity of many native Brook Trout populations (Kazyak et al 2018). The North Carolina Wildlife Resources Commission (NCWRC) has been involved with a long‐term effort to identify and genetically type wild Brook Trout populations within the state.…”

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Development of Genetic Baseline Information to Support the Conservation and Management of Wild Brook Trout in North Carolina

Kazyak

Lubinski

Rash

et al. 2021

N American J Fish Manag

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After centuries of declines, there is growing interest in conserving extant wild populations of Brook Trout Salvelinus fontinalis and reintroducing Brook Trout populations of native ancestry. A population genetic baseline can enhance conservation outcomes and promote restoration success. Consequently, it is important to document existing patterns of genetic variation across the landscape and translate these data into an approachable format for fisheries managers. We genotyped 9,507 Brook Trout representing 467 wild collections at 12 microsatellite loci to establish a genetic baseline for North Carolina, USA. Rarefied allelic richness (mean = 3.12) and observed heterozygosity (mean = 0.42), which reflect within‐population diversity, were low to moderate relative to levels typically observed at higher latitudes. Effective population sizes (Ne) varied widely but were often very low (151 collections had an estimated Ne < 10). Despite decades of intensive stocking across the state, we found little to no evidence of hatchery introgression in most populations. Although genetic variation was significant at a variety of spatial scales (mean pairwise = FST′ 0.73), substantial genetic variation occurred between patches within individual watersheds. Analysis of molecular variance indicated that a substantial portion (28.5%) of the observed genetic variation was attributable to differences among populations, with additional genetic variation among hydrologic unit codes (HUCs; 16.0, 16.6, 12.1, and 9.4% of the overall variation among 12‐, 10‐, 8‐, and 6‐digit HUCs, respectively). We discuss a suite of potential applications for this type of genetic data to enhance management outcomes, such as conservation prioritization and selection of source stocks for reintroductions or genetic rescue.

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Assessing the impact of stocking northern-origin hatchery brook trout on the genetics of wild populations in North Carolina

Cited by 21 publications

References 50 publications

Neutral Genetic and Phenotypic Variation within and among Isolated Headwater Populations of Brook Trout

Neutral Genetic and Phenotypic Variation within and among Isolated Headwater Populations of Brook Trout

Limited hatchery introgression into wild brook trout (Salvelinus fontinalis) populations despite reoccurring stocking

Development of Genetic Baseline Information to Support the Conservation and Management of Wild Brook Trout in North Carolina

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