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Multiple decades of stocking has resulted in limited hatchery introgression in wild brook trout (Salvelinus fontinalis) populations of Nova Scotia

Citation

Lehnert, Sarah et al. (2020), Multiple decades of stocking has resulted in limited hatchery introgression in wild brook trout (Salvelinus fontinalis) populations of Nova Scotia, Dryad, Dataset, https://doi.org/10.5061/dryad.rv15dv44w

Abstract

Many populations of freshwater fishes are threatened with losses, and increasingly, the release of hatchery individuals is one strategy being implemented to support wild populations. However, stocking of hatchery individuals may pose long-term threats to wild populations, particularly if genetic interactions occur between wild and hatchery individuals. One highly prized sport fish that has been heavily stocked throughout its range is the brook trout (Salvelinus fontinalis). In Nova Scotia, Canada, hatchery brook trout have been stocked since the early 1900s, and despite continued stocking efforts, populations have suffered declines in recent decades. Before this study, the genetic structure of brook trout populations in the province was unknown; however, given the potential negative consequences associated with hatchery stocking, it is possible that hatchery programs have adversely affected the genetic integrity of wild populations. To assess the influence of hatchery supplementation on wild populations, we genotyped wild brook trout from 12 river systems and hatchery brook trout from two major hatcheries using 100 microsatellite loci. Genetic analyses of wild trout revealed extensive population genetic structure among and within river systems and significant isolation-by-distance. Hatchery stocks were genetically distinct from wild populations, and most populations showed limited to no evidence of hatchery introgression (<5% hatchery ancestry). Only a single location had a substantial number of hatchery-derived trout and was located in the only river where a local strain is used for supplementation. The amount of hatchery stocking within a watershed did not influence the level of hatchery introgression. Neutral genetic structure of wild populations was influenced by geography with some influence of climate and stocking indices. Overall, our study suggests that long-term stocking has not significantly affected the genetic integrity of wild trout populations, highlighting the variable outcomes of stocking and the need to evaluate the consequences on a case-by-case basis

Methods

Details on data processing are provided in the manuscript. 

Usage Notes

Dataset of 100 microsatellite loci for wild and hatchery brook trout from Nova Scotia, Canada. Genetic data is provided as genepop format (Lehnert_Brooktrout_100Microsatellites.txt). Population code information are provided in a seperate csv file and in the manuscript (Pop_Names_Lehnert_Brooktrout_100micros.csv). Environmental and anthropogenic data are also included in csv format (Introgression_AnthroEnviro_data.csv) with a seperate csv describing variables (Introgression_AnthroEnviro_Description.csv). Proportion of hatchery introgression is provided with environemental and anthropogenic data. Least cost distance between sites is also provided in a csv file (LCDist_measured.csv). 

Funding

Nova Scotia Freshwater Fisheries Research Cooperative and Nova Scotia Department of Fisheries and Aquaculture

Fisheries and Oceans Canada (DFO) Genomics Research and Development Initiative (GRDI)