Has climate change altered Jan Mayen Island Arctic Charr life-history traits and feeding ecology?

Abstract The population of Arctic charr in Lake Nordlaguna on the Arctic island of Jan Mayen became landlocked by a volcanic eruption in AD 1732 that caused a coastal uplift closing the lake off from the sea. Although considered as a relatively productive lake in terms of planktonic primary production, the lake is relatively species poor in comparison to lakes in other parts of the Arctic. Jan Mayen has already undergone significant shifts in temperature, with mean open-water season temperatures having risen from 3.8 o C in the early 1960s (1960-65) to 5.6 o C in the 2015–2020 period. To assess how rising temperatures may have influenced Arctic charr life-history traits and feeding ecology, we conducted a test fishery in Lake Nordlaguna to evaluate whether current life-history strategies and trophic niche use of the resident population has shifted from the early 1960s as the climate has warmed. The results showed that smaller Arctic charr were larger and age-at maturity younger than in 1963–1965, however trophic niches appear to have remained stable. It is, therefore, suggested that the increased temperature over the last six decades at Jan Mayen has changed the Arctic charr life-history strategy to mature at younger ages due to a limited food supply. Additional genetic analyses did not show differentiation of trophic morph types, however, the Jan Mayen population as a whole is shown to be highly genetically distinct from Arctic charr in other North Atlantic locations.