| dc.description.abstract | Arctic char (Salvelinus alpinus) and Dolly Varden (S. malma) are the two most closely related species in the genus Salvelinus. Both species show substantial intraspecific variation in ecology, life history, morphology, and postglacial history across their distributional ranges, which has presented substantial challenges for conservation and management. Not only do char play important ecological roles within ecosystems, but they are also culturally, economically, and recreationally important. Char, and char fisheries, are a foundational element of Inuit culture in many coastal communities in the Canadian Arctic, and are critically important to food security due to their abundance and availability for year-round harvest. Char are also vulnerable to climate-induced changes in hydrology and water temperature due to their life stage-specific dependency on multiple habitats. Despite their importance and vulnerability, the genetics, ecology, and demography of anadromous (i.e., sea-run) chars are understudied, which makes it difficult to anticipate the effects of climate change and other stressors on species persistence.
In the central Canadian Arctic, there is uncertainty surrounding the distribution of Dolly Varden, as well as interspecific relationships between Dolly Varden and Arctic char in systems where they may be sympatric. Furthering understanding of the diversity of char species present in the central Canadian Arctic will enable scientists and local community members to more accurately and efficiently identify and restore critical habitats, thereby ensuring the viability of the critically important subsistence char fisheries. Through the application of western science methods and the gathering of traditional knowledge in Kugluktuk, Nunavut, this thesis aims to address knowledge gaps and uncertainties regarding char diversity and the composition of Salvelinus fishes in ecosystems in the central Canadian Arctic.
In Chapter 1, I provide a detailed overview of the postglacial history, ecology, and diversity of Arctic char and Dolly Varden. Arctic char and Dolly Varden have been studied extensively by scientists since the 1700s, and while several detailed reviews have been published on Arctic char over the past 40 years, Dolly Varden remain understudied. In addition, advances in the fields of genetics, ecology, and morphometrics have improved our understanding of the behavior, feeding, habitat requirements, postglacial histories, and intraspecific diversity within each of the two species. Chapter 1 focuses on placing findings from phylogenetic and morphometric studies from more recently published (through 2022) literature within the foundational context of earlier papers and reviews (since 1943) on Dolly Varden and Arctic char. Also included in this chapter are anticipated effects of climate change on the two species, and knowledge gaps and research priorities that, when addressed, will enable more informed conservation and management initiatives for these highly valued fishes. At the end of this chapter, I discuss how my research in chapters 2, 3, and 4 addresses known knowledge gaps.
Prior to the widespread use of genetics, closely related forms, morphs, and species of fishes were often differentiated using meristic characters. Analyses of meristic characters have provided researchers with a foundation upon which to build understanding of niche partitioning, sympatric speciation, and patterns of postglacial recolonization in taxa with complicated or contentious phylogenies, such as within the genus Salvelinus. In previous decades, meristic analyses have been used to investigate relationships between Arctic char and Dolly Varden, and to examine intraspecific diversity present within both species. Most individual studies have, however, focused on relatively small spatial scales. In Chapter 2, unpublished and previously published data from 374 populations and systems was collated to investigate whether two commonly used meristic characters – number of pyloric caeca and total number of gill rakers along the first gill arch – differed consistently between fish identified as either Arctic char or Dolly Varden. Analyses of population mean data from across the North American and Russian Arctic and sub-Arctic indicated that fish visually and/or genetically identified as Arctic char or Dolly Varden were consistently different in these two meristic characters across their distributional ranges. Five years of data collected from the Coppermine River, in the central Canadian Arctic, indicated that there was a population-level increase over time (from 1961 to 2020) in fish that were meristically Dolly Varden.
In the central Canadian Arctic, scientists long thought that all char east of the Mackenzie River were Arctic char. Recently, however, limited mitochondrial DNA data, as well as documentation from fishers in Kugluktuk, NU regarding variation in fish appearance, have suggested the presence of both Arctic char and northern form Dolly Varden (S. m. malma) in river systems in the central Canadian Arctic. Northern form Dolly Varden is a COSEWIC-listed Species of Special Concern in Canada, and an accurate understanding of the species’ range is critical to advance conservation and management efforts that are directed toward this important subsistence fish. In Chapter 3, data on morphometrics, individual meristics, and from the recently developed 87K Salvelinus SNP chip indicated presence of Dolly Varden in three systems east of the Mackenzie River; two systems, the Coppermine River and Darnley Bay, support sympatric anadromous Arctic char and Dolly Varden, while the third system, Tree River, supports solely Dolly Varden. Only one hybrid fish was detected in the analyses, in the Coppermine River; this may indicate that Arctic char and Dolly Varden maintain discrete spawning times and/or habitats, or that individuals of the two species either cannot or do not interbreed because of other unknown mechanisms or processes.
This project was community-partnered and driven by community concerns about the Coppermine River subsistence char fishery, and it was crucial to include the knowledge and voices of fishers and elders in the community. In Chapter 4, a summary of local and traditional knowledge interviews is presented. Interviews were conducted in Kugluktuk, Nunavut, a hamlet that sits at the mouth of the Coppermine River. Seventeen elders and fishers discussed their char fishing experiences, changes they have noticed in the Coppermine River over time, their concerns regarding a changing environment, and any additional research they would like to see done in the area. Many fishers observed decreases in char abundance over the past decade or so, though the char population appeared to rebound in summer 2022, and several participants believe the declines are a result of climate change. Fishers confirmed catching both Arctic char and Dolly Varden in the Coppermine River, but do not refer to or discriminate between the two species in the same way that western scientists do. The reports of Dolly Varden in the Coppermine River by fishers interviewed here aligns with the contemporaneous genomic, morphometric, and meristic data presented in Chapter 3.
In Chapter 5, I synthesized the work presented in chapters 1-4. Together, the results of this thesis confirm that both Arctic char and Dolly Varden are present in the central Canadian Arctic, indicating that the Mackenzie River does not represent a range boundary for Dolly Varden, as had been previously believed by western scientists. The presence of Dolly Varden in systems east of the Mackenzie River is supported by genomics, morphometrics, meristics, and local Inuit knowledge, and this research confirms long-held speculations and assertions – often based on limited data or anecdotal information – regarding the distribution of Dolly Varden in the Canadian Arctic. This is also the first detailed description of genetic and morphological characteristics of sympatric anadromous Arctic char and anadromous Dolly Varden in the Canadian Arctic. Incorporating both Inuit knowledge and western scientific data allowed us to gain a more comprehensive understanding of char diversity in the central Canadian Arctic, and will hopefully contribute to the ongoing community-based conservation and management of the Coppermine River subsistence char fishery. | en |
