Multi-indicator evidence for habitat use and trophic strategy segregation of two sympatric forms of Arctic char from the Cumberland Sound region of Nunavut, Canada

We analyzed Arctic char (Salvelinus alpinus (Linnaeus, 1758)) stable isotope ratios and fatty acid composition from two geographically proximal Nunavut lakes, Qasigiyat and Iqalugaarjuit, to determine if anadromous and resident Arctic char occupied different trophic niches. Resident Arctic char had lower delta C-13 and delta S-34, indicative of freshwater feeding, compared with anadromous individuals. Significantly lower delta N-15 of residents suggests the ecotypes feed at different trophic levels. Significantly wider delta C-13 and delta N-15 ranges in residents implied a broader trophic niche or a wider range in baseline prey isotope values. Results also provide further evidence for resident use of the estuarine environment in Qasigiyat. Immature Arctic char occupy a different trophic niche than both resident and anadromous fish within Iqalugaarjuit, but this relationship is less clear in Qasigiyat. Distinct stable isotope and fatty acid profiles indicate that resident and anadromous Arctic char have distinct trophic niches: marine for anadromous, freshwater for resident. Immature Arctic char seem to occupy a distinct niche from both anadromous and resident fish, which likely relates to use of both freshwater and estuarine environments, depending on developmental stage. We show the first evidence of the fatty acid differences and niche segregation between sympatric anadromous and resident ecotypes in Arctic char.

Automated summary

The study found that anadromous and resident Arctic char in two neighboring lakes in Nunavut occupy different trophic niches, with marine and freshwater food sources, respectively. Immature Arctic char occupy a distinct niche from both anadromous and resident fish, likely due to their use of both freshwater and estuarine environments depending on developmental stage.Distinct stable isotope and fatty acid profiles indicate that resident and anadromous Arctic char have unique trophic niches in the Arctic region.