Seasonal variability in transport of krill-like scattering into Bransfield Strait, Antarctic Peninsula, resolved from an array of echosounders

The seasonal transport of krill-like acoustic scattering into western Bransfield Strait, Antarctic Peninsula, was studied during a year-long deployment (December 01, 2022 to December 01, 2023) using a sub-surface mooring array of eight NORTEK Signature100 Acoustic Doppler Current Profilers. Subsurface moorings deployed in Gerlache and Boyd Straits, between Low and Hoseason Islands and off Cape Shirreff, Livingston Island, demonstrate that krill-like scattering have a similar seasonal cycle of transport at all locations. Upper Circumpolar Deepwater (UCDW, >1^oC, <180 mm kg^-1) was present in Boyd Strait until late summer, when it was rapidly replaced by colder, saline water. Acoustic returns of rill-like scattering peaked in late summer at all mooring locations, declined to background levels by late autumn, and remained at low levels throughout the winter. Transport of krill-like scattering through Boyd Strait was correlated with the seasonal presence of UCDW. These data indicate that the flux of krill into BS is not continuous. Therefore, the assumption that krill harvested in this region during the autumn and winter is replaced by sustained flux in a given season is flawed and will need to be carefully considered to achieve fishery management and conservation goals in the Antarctic Peninsula.