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.
| Original language | English |
|---|---|
| Pages (from-to) | 1069-1089 |
| Number of pages | 21 |
| Journal | Evolutionary Applications |
| Volume | 13 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - May 1 2020 |
Bibliographical note
Funding Information:The authors are grateful to anonymous reviewers for their insightful comments about this study. We also thank M. Lawton for their work in the laboratory at the Marine Gene Probe Laboratory, Dalhousie University. We thank Matthew Warner and Janice Nichol who provided assistance with fieldwork at several locations throughout Nova Scotia. We thank the Fraser's Mills Hatchery staff for their collections. This paper is part of a research project funded in part by the Nova Scotia Freshwater Fisheries Research Cooperative and Nova Scotia Department of Fisheries and Aquaculture (funds granted to S. Baillie through Dalhousie University). Microsatellite markers utilized were developed as part of a related project funded by Fisheries and Oceans Canada (DFO) Genomics Research and Development Initiative (GRDI). This paper would also not be possible without in-kind support through grants to P. Bentzen, Dalhousie University. Use of trade, product, or firm names is for descriptive purposes and does not imply endorsement by the Canadian federal or provincial governments. The findings and conclusions in this article are those of the authors and do not necessarily represent the views of the Nova Scotia Department of Fisheries and Aquaculture or DFO. This article is authorized by the Director of the U.S. Geological Survey.
Publisher Copyright:
© 2020 The Authors. Evolutionary Applications published by John Wiley & Sons Ltd
ASJC Scopus Subject Areas
- Ecology, Evolution, Behavior and Systematics
- Genetics
- General Agricultural and Biological Sciences