Using seabird and whale distribution models to estimate spatial consumption of Antarctic krill to inform fishery management

Ecosystem dynamics at the north-west Antarctic Peninsula are driven by complex interactions between physical and biological processes. For example, baleen whale populations are recovering from commercial harvesting against the backdrop of rapid climate change, including reduced sea-ice extent and changing ecosystem composition. Concurrently, the commercial demand for Antarctic krill is increasing, with the potential to increase the likelihood for competition with and between krill predators. However, understanding of the ecology, abundance, and spatial distribution of many krill predators is often limited, outdated, or at spatial scales that do not match those desired for effective fisheries management. We update current knowledge of predator dependence on krill resources by integrating recent telemetry-based data, at-sea observational surveys, regional estimates of predator abundance, and physiological data to estimate the spatial distribution of krill consumption during the austral summer by three species of Pygoscelis penguin, 11 species of flying seabirds, and one species of baleen whale (humpback whale, Megaptera novaeangliae). Our models show that the majority of important areas for krill-predator foraging are close to penguin breeding colonies in coastal areas where humpback whales also regularly feed. We show that krill consumption is highly variable across the region, and often concentrated at fine spatial scales, emphasising the need for management of the local krill fishery at relevant temporal and spatial scales. We highlight that despite less than comprehensive data, cetaceans are likely to consume a significant proportion of the krill consumed by natural predators, but are not currently considered directly in the management of the krill fishery. If management of the krill fishery is to remain precautionary and operate in a way that minimises the risks to krill predator populations, it is necessary to include up-to-date and precise abundance and consumption estimates for seals, fin-fish, squid, and other baleen whale species not currently considered.