Tanaidacean faunas of the Sea of Okhotsk and northern slope of the Kuril-Kamchatka Trench

Abstract The Sea of Okhotsk is one of the world’s largest marginal seas; its benthic fauna, especially from deeper parts, remains virtually unexplored. The material for this study was collected in the Sea of Okhotsk, Bussol Strait, and from the northern slope of the Kuril-Kamchatka Trench, during the Russian-German expedition Sea of Okhotsk Biodiversity Studies (SokhoBio) onboard the RV Akademik M.A. Lavrentyev in 2015. Material was collected using a camera-equipped epibenthic sledge (C-EBS). Forty-six tanaidacean species representing 31 genera and 12 families were found in 19 samples collected at depths from 1696 to 4798 m. All the species were new to science. The highest number of species (44) was recorded in the deepest part of the Sea of Okhotsk (Kuril Basin), followed by the northern slope of the Kuril-Kamchatka Trench (16 species) and the Bussol Strait (3 species). Almost one-third of all tanaidaceans (14 species) were common to both sides of the Kuril Island archipelago. Our results reveal a substantial faunal exchange between those two areas, although the small number of samples makes final conclusions about faunal similarity between the Sea of Okhotsk and the Pacific Ocean not fully possible. The level of rarity and patchiness of the tanaidacean fauna was high. The large number of species and individuals per sample observed in the Sea of Okhotsk might reflect high food availability in this area.