Estimating the average distribution of Antarctic krill at the northern Antarctic Peninsula

Antarctic krill are an important component of the Antarctic marine ecosystem, providing a key food source for many marine predator species. Additionally, krill are the target of the largest commercial fishery in the Southern Ocean, for which annual catches have been increasing in recent years. The krill fishery is managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), which has recently endorsed a new management framework that requires information about the spatial distribution and biomass of krill. Here, we model the seasonal (summer and winter) spatial habitat use of krill across the northern Antarctic Peninsula region, an area important to the commercial fishery. Using krill density estimates obtained from historical acoustic surveys and a GAMM framework, we model habitat properties associated with high krill biomass. During summer, krill density is elevated around Elephant Island and to the north of the South Shetland Islands, and our models show associations with the shelf break, increased sea-surface temperature, moderate chlorophyll-a concentration and increased salinity. During winter, krill density is elevated in the nearshore waters of the South Shetland Islands, and our models show associations with shallow waters with low sea-ice concentration, medium sea level anomaly, and medium current speed. Our models predict temporal averages of the distribution and density of krill, which can be used to aid the development of CCAMLR’s revised ecosystem approach to fisheries management in this region. We emphasise that our models provide descriptors of habitat characteristics, and do not necessarily identify key drivers of krill distribution. However, our models do have the potential to help in the spatial and temporal design and placement of future acoustic surveys that would preclude the future need for modelled extrapolations. We highlight that the ecosystem approach to fisheries management of krill critically depends upon such field observations at relevant spatial and temporal scales.