Dataset Information

Supplementation stocking of Lake Trout (Salvelinus namaycush) in small boreal lakes: Ecotypes influence on growth and condition.

ABSTRACT: Supplementation stocking is a commonly used management tool to sustain exploited fish populations. Possible negative consequences of supplementation on local stocks are a concern for the conservation of wild fish populations. However, the direct impacts of supplementation on life history traits of local populations have rarely been investigated. In addition, intraspecific hybridization between contrasting ecotypes (planktivorous and piscivorous) has been seldom considered in supplementation plans. Here, we combined genetic (genotype-by-sequencing analysis) and life history traits to document the effects of supplementation on maximum length, growth rates, body condition and genetic admixture in stocked populations of two Lake Trout ecotypes from small boreal lakes in Quebec and Ontario, Canada. In both ecotypes, the length of stocked individuals was greater than local individuals and, in planktivorous-stocked populations, most stocked fish exhibited a planktivorous-like growth while 20% of fish exhibited piscivorous-like growth. The body condition index was positively related to the proportion of local genetic background, but this pattern was only observed in stocked planktivorous populations. We conclude that interactions and hybridization between contrasting ecotypes is a risk that could result in deleterious impacts and possible outbreeding depression. We discuss the implications of these findings for supplementation stocking.

SUBMITTER: Morissette O

PROVIDER: S-EPMC6042763 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Publications

Supplementation stocking of Lake Trout (Salvelinus namaycush) in small boreal lakes: Ecotypes influence on growth and condition.

Morissette Olivier O Sirois Pascal P Lester Nigel P NP Wilson Chris C CC Bernatchez Louis L

PloS one 20180712 7

Supplementation stocking is a commonly used management tool to sustain exploited fish populations. Possible negative consequences of supplementation on local stocks are a concern for the conservation of wild fish populations. However, the direct impacts of supplementation on life history traits of local populations have rarely been investigated. In addition, intraspecific hybridization between contrasting ecotypes (planktivorous and piscivorous) has been seldom considered in supplementation plan ...[more]

PMID: 30001412

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Project description:Abstract Kinship‐based methods of population assessment such as close‐kin mark‐recapture require accurate and efficient genotyping methods capable of resolving complex relationships among kin. Inference of such relationships can be difficult using biallelic loci due to the large number of markers required to obtain the necessary power. Sequencing‐based microsatellite panels offer an efficient alternative, combining high polymorphism with efficient next‐generation methods. Here we construct, optimize, and test one such panel for lake trout (Salvelinus namaycush) using a combination of previously‐published loci adapted for sequencing and de novo loci mined from a genome assembly. We performed three rounds of primer optimization, yielding a final panel of 131 loci, followed by testing with two different levels of PCR multiplexing (all primers in one or two groups) and two different reaction volumes (5 and 10 μL). Our results showed that the use of the largest multiplex and smallest reaction volume did not substantially change results, allowing significant cost and time savings. To test panel accuracy, we used both a set of 153 known‐origin samples from origins of management interest and a series of hatchery crosses representing nine families with parent‐offspring, half‐sibling, and largely‐unrelated pairs. Our results indicate that sequencing‐based microsatellite panels can efficiently and accurately provide the information required for a population genetics analyses including population assignment, calculation of between‐population FST, and kinship‐based population estimation techniques. Such techniques are seeing increasing applications for a wide range of taxa; our findings should provide insight and guidance for the development of the necessary molecular resources. Kinship‐based methods of population assessment such as close‐kin mark‐recapture require accurate and efficient genotyping methods capable of resolving complex relationships among kin, but inference of such relationships can be difficult using biallelic loci. Sequencing‐based microsatellite panels offer an efficient alternative, combining high polymorphism with efficient next‐generation methods. Here we construct, optimize, and test one such panel for lake trout (Salvelinus namaycush) using a combination of historical loci adapted for sequencing and de novo loci mined from a genome assembly.

Project description: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.

Dataset Information

Supplementation stocking of Lake Trout (Salvelinus namaycush) in small boreal lakes: Ecotypes influence on growth and condition.

Publications

Supplementation stocking of Lake Trout (Salvelinus namaycush) in small boreal lakes: Ecotypes influence on growth and condition.

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