| Summary: | First online: 24 April 2015 Current trends of fish communities in the interior Arctic Ocean are largely unknown, whereas more fishes of boreal origin are reported from the Chukchi and Barents Seas recently. To assess variability in species composition and spatiotemporal occurrence in ichthyoplankton in the southeast Beaufort Sea, we sampled larval and juvenile fish using square-conical nets in the upper water column (<100 m) from June to September between 2002 and 2011. Gadidae consisting of Boreogadus saida and Arctogadus glacialis numerically accounted for >75 % of total catches every month. Cottidae and Liparidae usually followed Gadidae, together representing 9–94 % of non-gadid species in number. The majority of dominant and subdominant species occurred ubiquitously through the sampling area, whereas Gymnocanthus tricuspis (Cottidae), Liparis gibbus (Liparidae), and Leptoclinus maculatus (Stichaeidae) occurred abundantly on the Mackenzie Shelf. In contrast, Triglops nybelini (Cottidae) was frequently found in the Amundsen Gulf, which was characterized by higher salinities (>25). Exceptional species composition was observed in September 2011, when Ammodytes hexapterus (Ammodytidae) numerically accounted for 67 % of non-gadid species. In the southeast Beaufort Sea, summer ichthyoplankton are characterized by the overwhelming dominance of Arctic gadids as well as the frequent occurrence of Arctic cottids and liparids. However, the sudden and frequent occurrence of A. hexapterus may be a first sign of significant changes in fish communities in the interior Arctic Ocean.
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