A deep scattering layer under the North Pole pack ice

The 3.3 million km2 marine ecosystem around the North Pole, defined as Central Arctic Ocean (CAO), is a blind spot on map of world’s fish stocks. CAO essentially comprises permanently ice-covered deep basins and ridges outside continental shelves, only accessible by ice-breakers. Traditional trawling for assessing stocks impossible under thick pack ice, coherent hydroacoustic surveys are unachievable due to ice-breaking noise. Consequently, nothing known about existence any pelagic in CAO, although juveniles Boreogadus saida richly occur at surface associated with sea ice ice-associated Arctogadus glacialis has been reported well. We here present first indication possible mesopelagic stock CAO. had opportunity analyse geophysical data set 13 time windows usable acoustic over transect from 84.4 °N Nansen Basin, across Pole (90.0 °N), 82.4 Canada Basin. discovered scattering layer (DSL), suggesting presence zooplankton fish, 300–600 m depth Atlantic water Maximum abundance biomass was very low; values ca. 2,000 individuals km−2 50 kg were calculated DSL North-Pole area according model assuming that all backscatter represents 15-cm long B. and/or A. glacialis. true even lower than this, but cannot be quantified this dataset originating pneumatophores physonect siphonophores area. Further studies should include sampling identification backscattering organisms. From our study we can conclude if central contains their currently too low sustainable fishery.