The Capelin invasion: evidence for a trophic shift in Arctic Char populations from the Cumberland Sound region, Nunavut, Canada

Climate change is having myriad effects on Arctic marine ecosystems and food webs. Anadromous Arctic Char, Salvelinus alpinus (Linnaeus, 1758), feed intensively at sea during summer. In Cumberland Sound, Nunavut, Canada, there has been a recent increased availability of a forage fish, Capelin. To investigate changes over time in Arctic Char foraging, we assessed Arctic Char trophic niche from 2002 to 2011 using stomach content analysis and stable isotope analysis (delta C-13 and delta N-15) of muscle tissue from two river/lake systems, Isuituq and Kipisa. We also compared population characteristics by calculating Fulton's condition factor (K) and by fitting von Bertalanffy growth curves with length-at-age data. Results revealed Capelin were newly present in the diets of Arctic Char in 2011, describing a shift from a primarily invertebrate-based to a fish-based diet. No trend in delta N-15 over time suggests that the trophic level of Arctic Char has not changed; however, the delta C-15 for both systems converged in 2011 on a value suggestive of feeding on Capelin. Growth curves and length-at-age analyses suggest that foraging on Capelin may have increased individual growth. Changes in the growth and condition of Arctic Char in this region could have significant economic and cultural implications.

Automated summary

The study reveals a shift in the diet of Arctic Char from primarily invertebrate-based to fish-based, with an increased presence of Capelin in their diets. While the trophic level of Arctic Char remained unchanged, feeding on Capelin appeared to enhance individual growth starting from 2011.