David J. Yurkowski

Parasites play a critical yet understudied role in Arctic ecosystems, particularly within key subsistence species such as Arctic char ( Salvelinus alpinus ). As the Arctic undergoes rapid climate-driven change, establishing baseline parasite biodiversity is essential for monitoring ecological shifts and anticipating emerging health and conservation concerns. This study provides the most comprehensive assessment to date of Arctic char parasites in the North American Arctic by integrating a systematic literature review with new empirical data from 378 Arctic char collected across five Nunavut areas (2020–2024). The literature review (30 studies, 1956–2024) documented 67 parasite taxa—48 identified to species—with helminths (nematodes, cestodes, trematodes, acanthocephalans) dominant. Overall, 82% of taxa occurred in anadromous Arctic char and 54% in freshwater forms, including 22 species unique to anadromous fish. Our empirical assessment identified 35 parasite taxa—23 to species level—including several previously unreported from Arctic char in this region. Common and widespread parasites documented in the empirical assessment included Brachyphallus crenatus , Derogenes varicus , Bothrimonus sturionis , and Alloopistholecithum gibbosum , although notable spatial variation occurred in community composition and infection intensity. The occurrence of rare and previously unreported parasites may suggest emerging shifts in host–parasite dynamics potentially linked to changing prey availability and northward species range expansions. Together, these findings establish an essential baseline for Arctic char parasite biodiversity and highlight the need for continued monitoring to track future changes driven by climate warming, shifting food webs, and their implications for fish health and food security in northern Indigenous communities.

Prey availability and predation risk drive animal distribution, movement, and foraging ecology, yet studies rarely analyse multiple predator–prey levels together. Understanding how predators optimise risk–reward tradeoffs is important for species conservation and management, especially in systems facing extreme ecosystem change. We examined how top‐down (modelled polar bear habitat selection) and bottom‐up (modelled fish diversity) processes influence the habitat selection, movement, and foraging behaviour of 26 ringed seals (greater than 70,000 dives and 10,000 locations over 877 seal days). Our results suggest that polar bears spatially restrict seal movements and reduce the time seals spend foraging, potentially decreasing foraging success. Seals were more likely to be present and dive longer in high‐predation risk areas when prey diversity was high. Further, seal habitat selection models excluding polar bears overestimated core space use. These findings illustrate the dynamic tradeoffs that mesopredators make when balancing predation risk and resource acquisition.

The Arctic is undergoing rapid declines in sea ice and changes in Arctic ecosystems. The diet of one of the Arctic’s most abundant seabirds, the black-legged kittiwake ( Rissa tridactyla), has been used as an indicator of ecosystem changes in the European Arctic, yet little is known about their diet in the Canadian Arctic. We quantified the stomach contents of kittiwakes near Qikiqtarjuaq and Mittimatalik (Pond Inlet), Nunavut, in the Canadian Arctic, and assessed if stable carbon (δ ¹³ C) and nitrogen (δ ¹⁵ N) isotopes in livers differed from that of the dominant prey in their stomachs. Based on stomach contents, prey did not significantly differ between regions, where the dominant prey was Arctic cod ( Boreogadus saida). However, after accounting for dietary discrimination, δ ¹³ C and δ ¹⁵ N values of kittiwake liver were at a lower trophic level than that of Arctic cod muscle. Thus, while kittiwakes do readily consume Arctic cod, stomach content analysis may underestimate soft tissue prey in their diet, such as invertebrates. Future research should include regurgitate and faecal samples to better understand kittiwake diet in the Canadian Arctic. Nevertheless, as climate change impacts continue to increase, this study provides important benchmark information for monitoring changes in these Arctic-breeding seabirds.

The Lasting Ice Area along the northern coastline of Ellesmere Island and Greenland will be the region where Arctic multiyear sea ice will persist the longest in a warming climate, making this area critical for ice-dependent species. In 2019, the Tuvaijuittuq Marine Protected Area was established for the interim protection of the waters off northern Ellesmere Island. We present the first comprehensive study of the Archer Fiord–Lady Franklin Bay system located at the northern end of Nares Strait, in the Tuvaijuittuq area. Data on the hydrography, biogeochemical cycles, pelagic and benthic productivity, and seabed sediment were collected along a nearshore-offshore transect. The region is influenced by meteoric waters as well as Pacific and Atlantic-derived waters, and likely acts as a strong seasonal CO ₂ sink. Despite fall-bloom conditions, low primary, secondary, and benthic productivity contrasted with the relatively high abundance of marine mammals. This productivity paradox either suggests (1) that organic matter and detritus deposited and accumulated over long periods prior to our survey sustain the benthic community on which marine mammals depend for foraging; (2) local productivity hotspots in areas outside the sampled stations; or (3) a highly efficient system with minor production surpluses. Solving this paradox will require further surveys in the area.

Marine megafauna species are affected by a wide range of anthropogenic threats. To evaluate the risk of such threats, species’ vulnerability to each threat must first be determined. We build on the existing threats classification scheme and ranking system of the International Union for Conservation of Nature (IUCN) Red List of Threatened Species by assessing the vulnerability of 256 marine megafauna species to 23 at‐sea threats. The threats we considered included individual fishing gear types, climate‐change‐related subthreats not previously assessed, and threats associated with coastal impacts and maritime disturbances. Our ratings resulted in 70 species having high vulnerability ( v > 0.778 out of 1) to at least 1 threat, primarily drifting longlines, temperature extremes, or fixed gear. These 3 threats were also considered to have the most severe effects (i.e., steepest population declines). Overall, temperature extremes and plastics and other solid waste were rated as affecting the largest proportion of populations. Penguins, pinnipeds, and polar bears had the highest vulnerability to temperature extremes. Bony fishes had the highest vulnerability to drifting longlines and plastics and other solid waste; pelagic cetaceans to 4 maritime disturbance threats; elasmobranchs to 5 fishing threats; and flying birds to drifting longlines and 2 maritime disturbance threats. Sirenians and turtles had the highest vulnerability to at least one threat from all 4 categories. Despite not necessarily having severe effects for most taxonomic groups, temperature extremes were rated among the top threats for all taxa except bony fishes. The vulnerability scores we provide are an important first step in estimating the risk of threats to marine megafauna. Importantly, they help differentiate scope from severity, which is key to identifying threats that should be prioritized for mitigation.

Rapid warming in the Arctic is causing cumulative impacts on ecosystems, including widespread reduction in sea ice extent, resulting in shifts in primary production, which can have cascading bottom‐up trophic influences on marine food web structure and function. Understanding trophic interactions and the structure of local food webs across the Canadian Arctic remains fragmented, yet it is essential to inform conservation efforts and provide a comparative reference to assess future food web shifts driven by climate change. We used stable isotope analysis (δ¹³C and δ¹⁵N) to determine the isotopic niche dynamics (e.g., size and overlap) and trophic positions among invertebrates, fishes and marine mammals sampled from 2015 to 2019 to quantify the trophic interactions and trophic structure of the Eclipse Sound food web. Mean trophic positions ranged from 2.0 for copepods to 4.4 for sea tadpoles, with some individuals, such as narwhal and ringed seals, occupying a trophic position of 5.3, indicating a marine food web that spans at least four trophic levels. Across taxonomic groups, isotopic niche size was largest in the invertebrate taxonomic group (7.87‰²), followed by fishes (3.26‰²) and then marine mammals (2.03‰²). The core isotopic niche overlap between taxonomic groups ranged from no overlap between invertebrates and fishes, or between marine mammals and invertebrates and 44% overlap between fishes and marine mammals. Overall, we present the marine food web structure of over 50 species of invertebrates, fish and mammals during the open‐water period in Eclipse Sound, Nunavut, and provide a reference point for future assessments of food web dynamics and conservation goals.

The recent Kunming-Montreal Global Biodiversity Framework (GBF) sets ambitious goals but no clear pathway for how zero loss of important biodiversity areas and halting human-induced extinction of threatened species will be achieved. We assembled a multi-taxa tracking dataset (11 million geopositions from 15,845 tracked individuals across 121 species) to provide a global assessment of space use of highly mobile marine megafauna, showing that 63% of the area that they cover is used 80% of the time as important migratory corridors or residence areas. The GBF 30% threshold (Target 3) will be insufficient for marine megafauna’s effective conservation, leaving important areas exposed to major anthropogenic threats. Coupling area protection with mitigation strategies (e.g., fishing regulation, wildlife-traffic separation) will be essential to reach international goals and conserve biodiversity.