Temporal patterns in South Georgia (48.3) zooplankton: insights from a moored echosounder

Antarctic krill (Euphausia superba) are a key species in the Southern Ocean ecosystem, supporting large populations of higher predators, contributing to the sequestration of carbon and the subject of a fishery. Here we detail the deployment and results from 4 years of moored 120 kHz EK80 echosounder data from South Georgia. These data indicate considerable seasonal and interannual variability in krill swarm presence, size and shape. Importantly our results highlight considerably more acoustic backscatter at night during winter months that conventional daytime only surveys would miss. We discuss these results in the context of challenges and opportunities for the increased use of moorings in the Southern Ocean to monitor krill stocks and behaviour.