Modelling the distribution of Antarctic krill at the South Orkney Islands: the impact of krill behaviour on large-scale population connectivity

The importance of Antarctic krill (Euphausia superba) in the Southern Ocean ecosystem has long been known. As both a major food source for multiple predators and the target of a commercial fishery, understanding the key physical and behavioural drivers for krill distribution is essential, particularly for the development of risk management strategies for the fishery.

The South Orkney Islands region, in the southwest Atlantic sector of the Southern Ocean, is one of the main fishing grounds for krill and also critical for determining the overall availability of krill downstream across the wider Scotia Sea. Here we present results from a modelling project investigating the large-scale flux of krill into the South Orkney region.

Using the NEMO 1/12^o ocean-sea ice model to drive an individual-based model (IBM) parameterised for krill, we investigate the influence of oceanographic and sea-ice variability on transport of krill into the South Orkney region from upstream regions, specifically the western Antarctic Peninsula and Weddell Sea. Aspects of krill behaviour (diel vertical migration, association with sea ice) are implemented in the IBM to examine the impact these traits may have on krill distribution at large scales. The model suggests that the behaviour of krill under sea ice affects both the pathways and timing of transport to the region, increasing the probability of influx from the western Antarctic Peninsula and decreasing mean transport time. Vertical migration further modifies the patterns of krill flux to the region. The sensitivity of the modelled population connectivity to krill behaviour is an important consideration for future studies investigating the distribution of Antarctic krill.