Fish species, habitat, and capture location outweigh fish mass as drivers of microplastic pollution in Canadian Arctic fishes

Fishes are key indicators of ecosystem health and are important food sources for Indigenous peoples. Although fishes have been shown to ingest microplastics (MPs; plastic particles <5 mm long) in localities between the polar regions and equator, very few investigations focus on the drivers of microplastic pollution in Arctic fishes. We investigated MPs in 435 stomachs and gastrointestinal (GI) tracts of 7 freshwater fish species from the Canadian Arctic and tested for correlations with habitat, capture location, surrounding human population, and stomach/GI tract mass. Overall, an average 2.22 ± 3.51 MPs per fish was determined following blank and polymer composition normalizations. Northern pike (Esox lucius) contained the greatest average microplastic abundance (3.59 ± 5.09 MPs/fish), the highest percentage of individuals containing MPs (86%), and as a demersal species, contained significantly more MPs than pelagic and benthic fishes. Fishes captured from the Great Slave Lake location contained significantly more total MPs (mean 3.41 ± 4.40 MPs/fish) than fishes from four other studied locations, which may be explained by the greater human population around Great Slave Lake. Fish captured from lakes on the more remote and sparsely populated Cornwallis Island, however, contained significantly greater micro-fragment concentrations, which suggests that proximity to localized anthropogenic activities can influence microplastic concentrations. We found no relationship between stomach/GI tract mass and microplastic abundance. Our study provides a crucial baseline for long-term monitoring of MPs in Arctic fishes, as it assesses the main factors contributing to microplastic ingestion in over 400 freshwater fish and in multiple fish species at 18 capture sites.