Shifts in the composition and distribution of Pacific Arctic larval fish assemblages in response to rapid ecosystem change

Abstract

The Pacific Arctic marine ecosystem has undergone rapid changes in recent years due to ocean warming, sea ice loss, and increased northward transport of Pacific‐origin waters into the Arctic. These climate‐mediated changes have been linked to range shifts of juvenile and adult subarctic (boreal) and Arctic fish populations, though it is unclear whether distributional changes are also occurring during the early life stages. We analyzed larval fish abundance and distribution data sampled in late summer from 2010 to 2019 in two interconnected Pacific Arctic ecosystems: the northern Bering Sea and Chukchi Sea, to determine whether recent warming and loss of sea ice has restricted habitat for Arctic species and altered larval fish assemblage composition from Arctic‐ to boreal‐associated taxa. Multivariate analyses revealed the presence of three distinct multi‐species assemblages across all years: (1) a boreal assemblage dominated by yellowfin sole (Limanda aspera), capelin (Mallotus catervarius), and walleye pollock (Gadus chalcogrammus); (2) an Arctic assemblage composed of Arctic cod (Boreogadus saida) and other common Arctic species; and (3) a mixed assemblage composed of the dominant species from the other two assemblages. We found that the wind‐ and current‐driven northward advection of warmer, subarctic waters and the unprecedented low‐ice conditions observed in the northern Bering and Chukchi seas beginning in 2017 and persisting into 2018 and 2019 have precipitated community‐wide shifts, with the boreal larval fish assemblage expanding northward and offshore and the Arctic assemblage retreating poleward. We conclude that Arctic warming is most significantly driving changes in abundance at the leading and trailing edges of the Chukchi Sea larval fish community as boreal species increase in abundance and Arctic species decline. Our analyses document how quickly larval fish assemblages respond to environmental change and reveal that the impacts of Arctic borealization on fish community composition spans multiple life stages over large spatial scales.

Patterns of summer ichthyoplankton distribution, including invasive species, in the Bering and Chukchi Seas

“…Considering a previous study, E. gracilis is more distributed northward than in previous reports because this species is mainly distributed between 66.5°N and 69.5°N (Vestfals et al, 2019;Baker, 2021;Levine et al, 2023). According to the previous studies, they are moving northward as the water temperature increases due to global warming (De Robertis et al, 2017;Baker et al, 2020;Axler et al, 2023;Levine et al, 2023). Furthermore, B. glaciale, typically distributed in the Atlantic Arctic region, was observed in the present study.…”

“…In the Pacific Arctic, mainly in the Chukchi Sea, B. saida was the most dominant species, which is a typical Arctic fish (Eisner et al, 2013;Marsh et al, 2020;Baker et al, 2022;Axler et al, 2023;Cooper et al, 2023;Levine et al, 2023). In the Pacific sub-Arctic region, including the Bering Sea and Bering Strait, G. chalcogrammus and P. quadrituberculatus were the dominant and subdominant species, respectively (Eisner et al, 2013;Vestfals et al, 2019;Axler et al, 2023). Therefore, it is thought that the Bering Strait represented a more similar community structure to the Bering Sea than the Chukchi Sea in the summer season.…”

“…That is, the ichthyoplankton community was divided into two major groups, groups C and D. Group C consisted of the Pacific Arctic stations. The species that most contributed to the group similarity in the SIMPER analysis was B. saida, which is a typical dominant species in the Pacific Arctic region (Eisner et al, 2013;De Robertis et al, 2017;Vestfals et al, 2019;Axler et al, 2023). On the other hand, group D was composed of Pacific sub-Arctic stations.…”

“…On the other hand, group D was composed of Pacific sub-Arctic stations. The species that contributed to the group similarity were G. chalcogrammus and S. leucopsarus, which commonly dominate in the Pacific sub-Arctic of the northern Pacific region (Pearcy et al, 1979;Beamish et al, 1999;Moku et al, 2000;Eisner et al, 2013;Majewski et al, 2017;Axler et al, 2023). Consequently, the two groups were thought to be made up of the typical ichthyoplankton community structure in each region.…”

When species don’t move together: Non-concurrent range shifts in Eastern Pacific kelp forest communities

“…There is evidence that as ranges shift, movement of separate species will create ecological mismatches altering community composition and abundance [14,15] leading to reshaped trophic dynamics. Mismatched range movement has caused the restructuring of plankton communities with subsequent impacts on higher trophic level grazers [16].…”