Competition or coexistence? Krill utilisation by marine predators and the krill fishing industry

Abstract

**Abstract:** The Southern Ocean provides important breeding and foraging habitats for numerous marine predators, many of which rely on Antarctic krill Euphausia superba as their main prey item. Krill are also the target of a commercial fishery, which has the potential to reduce prey availability to dependent predator species. Alternatively, krill-dependent predators and the krill fishing industry may co-exist with no negative impacts if krill is abundant and catch limits account for predator requirements. In order to manage the krill fishery in such a way as to limit potential negative impacts on marine predators it is important to identify areas which are important to krill-dependent predators. We have developed a suite of habitat models, to predict the density distributions of 14 species of krill-dependent predators including penguins (3 species), procellariform seabirds (8 species) and cetaceans (2 species) during austral summer. Additionally, we have estimated the total krill consumption by each predator species by collating energy requirements and diet composition from the scientific literature. By combining species-specific estimates of krill consumption with species distributions predicted from our habitat models we have created a series of spatially explicit estimates of krill consumption across the Antarctic Peninsula and South Shetland Islands. We found high inter-specific variation in the spatial distribution of krill consumption, and some overlap between predator consumption and the krill fishery. However, understanding the possible impacts of the fishery on marine predators remains challenging due to important gaps in our understanding. These include i) spatio-temporal mismatches between predator data and the krill fishery, ii) the impact of krill transport, downstream impacts and replenishment rates, iii) disruption of krill swarms, and iv) seasonal variation. **Authors:** Victoria Warwick-Evans¹, Luciano Dalla Rosa², Jefferson Hinke³, Norman Ratcliffe¹, Jarrod Santora⁴, Eduardo Secchi², Elisa Seyboth², James Waggitt⁵, Phil Trathan¹ ¹British Antarctic Survey, ²Federal University of Rio Grande, ³NOAA, ⁴University of California Santa Cruz, ⁵Bangor University