Consequences of Stocking Headwater Impoundments on Native Populations of Brook Trout in Tributaries

Humston, Robert; Bezold, Kelly; Adkins, Nathaniel D.; Elsey, Ryan J.; Huss, Jessica; Meekins, Brent A.; Cabe, Paul R.; King, Timothy L.

doi:10.1080/02755947.2012.661385

Cited by 10 publications

(7 citation statements)

References 45 publications

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“…Our results corroborate those by Humston et al. () and suggest variable, but overall lower degrees of introgression than other studies of stream salmonids (see Fleming & Petersson, for comparison). Of note, all sites comprised of >10% introgressed individuals are not directly stocked by PFBC or cooperative nurseries, including one site (CONK) which has no record of stocking for over 50 years and is isolated by a downstream impoundment.…”

Section: Discussionsupporting

confidence: 92%

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

White

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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Section: Discussionsupporting

confidence: 92%

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

White

Miller

Dowell

et al. 2018

Evolutionary Applications

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“…Potential wild‐hatchery introgression was identified based on the proportion of membership ( q ) to a genetic cluster associated with a hatchery strain, with q ≥ 0.10 used as a minimum. Prior studies have determined this threshold q ‐value to produce the highest proportion of correctly assigned pure and hybrid individuals (Vähä & Primmer, ) and have been previously used to examine hatchery introgression in Brook Trout (Harbicht et al, ; Humston et al, ).…”

Section: Methodsmentioning

confidence: 99%

“…Prior studies have determined this threshold q-value to produce the highest proportion of correctly assigned pure and hybrid individuals (Vähä & Primmer, 2006) and have been previously used to examine hatchery introgression in Brook Trout (Harbicht et al, 2014;Humston et al, 2012).…”

Section: Population Admixture and Hatchery Introgressionmentioning

confidence: 99%

Genetic diversity, admixture, and hatchery influence in Brook Trout (Salvelinus fontinalis) throughout western New York State

Beer

Cornett

Austerman

et al. 2019

Ecology and Evolution

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Although Brook Trout are distributed across most of eastern North America, population numbers have declined in many regions due to habitat loss, climate change, and competition with non‐native species. In New York State, Brook Trout habitat has been substantially reduced, with many areas showing complete extirpation of Brook Trout populations, predominantly in the western portion of the state. Small, fragmented populations are at risk of genetic diversity loss, inbreeding depression, and reduced fitness, leading to a greater potential for local extirpation. Genetic monitoring is a practical tool that can facilitate further conservation‐decision making regarding small populations. In this study, we used 12 microsatellite loci to examine 3,436 sampled Brook Trout, representing 75 sites from the Allegheny, Erie/Niagara, Genesee, Oswego, Lake Ontario, and Susquehanna drainage basins throughout western New York State. Three Brook Trout hatchery strains were also genetically characterized to evaluate the degree of hatchery introgression between wild populations and hatchery strains stocked in the region. Overall, estimates of genetic diversity varied widely: Allelic richness ranged from 2.23 to 7.485, and expected heterozygosity ranged from 0.402 to 0.766. As observed for Brook Trout in other regions, we found a high degree of genetic differentiation among populations, with all comparisons except one showing significant F ST values. Hatchery introgression was found to be minimal, with estimates ranging from 1.96% to 3.10% of wild individuals exhibiting membership proportions to a hatchery strain cluster exceeding 10% ( q ≥ 0.10). Results from this investigation can be used to prioritize management efforts for Brook Trout in western New York State and act as a baseline to monitor future population trends.

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“…Natural resource agencies also trap juvenile salmon smolts and haul them downstream with barges and trucks in the Columbia River Basin to minimize cumulative mortality associated with multiple dam passages (Muir, Marsh, Sandford, Smith, & Williams, ; Naughton, Bennett, & Newman, ; Schreck, Stahl, Davis, Roby, & Clemens, ). Conservation hatchery operations rear at‐risk species such as Brook Trout Salvelinus fontinalis and Pallid Sturgeon Scaphirhynchus albus and translocate individuals to natural systems within their native range to augment populations (Humston et al, ; Steffensen, Powell, & Koch, ). Colorado River Cutthroat Trout O ncorhynchus clarki pleuriticus collected from donor populations were translocated to streams where models predicted reintroduction efforts would likely be successful (Harig & Fausch, ).…”

Section: Introductionmentioning

confidence: 99%

Identifying optimal hauling densities for adult Chinook salmon trap and haul operations

Colvin

Peterson

Sharpe

et al. 2018

River Research & Apps

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Trap and haul programmes are used to conserve fish populations by circumventing high mortality locations or events and enhancing population abundance by reintroducing fish to historical habitats and mitigating for fish passage limitations. Spring-run Chinook salmon are transported in trucks upstream of barrier dams in Willamette River Tributaries as part of fish conservation efforts. Fish mortalities occurring during hauling minimize the utility of the effort because natural origin fish are targeted for theses outplanting efforts. The objectives of this study were to develop models predicting hauling mortality and identify optimal hauling densities that minimize mortality risk and effort. We used an information-theoretic approach to evaluate multiple models predicting hauling mortality. Predictors identified varied between the two dams evaluated but were related to operations and annual or in-river conditions. The amount of time loading fish and the density of fish in tank trucks were positively associated with hauling mortality. Instream flows and thermal exposure were also identified as factors predicting with hauling mortality. We used the results of model selection to predict mortality risk and calculate daily hauling effort. Risk and effort were combined into a utility to identify optimal hauling densities for varying numbers of fish to haul and transport truck volume. Optimal hauling densities varied between dams reflecting whether loading time or hauling density was associated with hauling mortality. This analysis provides managers a way to integrate research, monitoring, and management to improve understanding of factors associated with hauling mortality and adjust optimal hauling densities using adaptive management.

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Consequences of Stocking Headwater Impoundments on Native Populations of Brook Trout in Tributaries

Cited by 10 publications

References 45 publications

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

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

Genetic diversity, admixture, and hatchery influence in Brook Trout (Salvelinus fontinalis) throughout western New York State

Identifying optimal hauling densities for adult Chinook salmon trap and haul operations

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