Trophic ecology of culturally important subsistence fish species and assessment of diet overlap with range-expanding chum salmon (Oncorhynchus keta) in the Canadian Arctic
Creators: Wight, Kevin James
Publisher: name: University of Alberta Library
Year: 2024

<p>Rapid climate change is occurring in the Arctic and has the potential to affect the diets and trophic dynamics of northern fish species, many of which hold great cultural value to northern communities. Fully understanding the trophic ecology of such fishes allows us to better understand their environmental niche, and being able to identify key prey items allows us to determine if key food sources are threatened by environmental changes. This allows for predictions to be made regarding the adaptation potential of fishes in the face of changing ecosystems. Additionally, global increases in water temperatures introduces the potential for opportunistic fish species to expand their ranges northward, making trophic interactions with endemic northern fishes a possibility. Understanding the trophic ecology of northern and range-expanding fishes allows us to predict the potential for trophic interactions and potentially competition, and whether or not a range expanding species may fill a vacant feeding niche in a novel environment, or if it will overlap with endemic fishes.<br><br>
To assess the trophic dynamics of northern fishes, I first conducted a systematic literature review on the diets of eight fish species: Arctic char (Salvelinus alpinus), Dolly Varden (S. malma), lake trout (S. namaycush), bull trout (S. confluentus), inconnu (Stenodus leucichthys), broad whitefish (Coregonus nasus), lake whitefish (C. clupeaformis), and burbot (Lota lota). These species chosen for their importance as subsistence fishes to northern communities. This review highlighted the commonality of adaptable, generalist diets in most species, an adaptation to the harsh and variable nature of Arctic systems where prey availability can be sporadic and unpredictable. Additionally, this review highlighted several knowledge gaps regarding the trophic ecology of northern fishes, particularly for inconnu, broad whitefish, and bull trout. Additionally, trophic studies outside of the summer months are very uncommon, resulting in a large temporal knowledge gap for most species.<br>
Next, I analyzed the diets of range-expanding chum salmon (Oncorhynchus keta) caught by subsistence harvesters in the Mackenzie River basin of the Northwest Territories in order to address questions regarding the species diet and potential to compete with endemic subsistence fishes such as Dolly Varden, lake trout, and inconnu. I found that, while most salmon caught had ceased feeding upon entering fresh water, 5% of salmon sampled had recently fed while in fresh water, a deviation from established life history characteristics of Pacific salmon. Prey eaten by salmon included freshwater crustaceans, water boatmen (Family: Corixidae), least cisco, and a small bird. Despite this, the infrequency of freshwater feeding suggests that dietary interactions between salmon and the northern fishes used for comparative analyses is unlikely. This is supported by the results of stable isotope analyses, which demonstrate that salmon do not overlap with any of the endemic northern fishes on the basis of trophic level, and only Dolly Varden overlapped with chum salmon in terms of feeding habitat <br>
My results suggest that potential for trophic niche overlap between chum salmon and Arctic freshwater fishes is not high, although more thorough analyses are needed to confirm this. Additionally, some chum salmon in the Arctic environment are exhibiting alterations from known life history traits of those found in their southern distribution. This work has implications for the management of chum salmon in the new environments to which they are expanding by demonstrating their ability to adapt to new settings, as well as the feeding niche they occupy in Arctic ecosystems. This work also has implications for the management of northern fishes by demonstrating the low risk of trophic niche overlap with a range-expanding counterpart, as well as addressing knowledge gaps regarding the trophic ecology and feeding niches of northern fishes.</p>