Aim: Marine protected areas can serve to regulate harvesting and conserve biodiversity. Within large multi-use MPAs, it is often unclear to what degree critical sites of biodiversity are afforded protection against commercial activities. Addressing this issue is a prerequisite if we are to appropriately assess sites against conservation targets.We evaluated whether the management regime of a large MPA conserved sites (Key Biodiversity Areas, KBAs) supporting the global persistence of top marine predators.Location: Southwest Atlantic Ocean. Method:We collated population and tracking data (1,418 tracks) from 14 marine predator species (Procellariiformes, Sphenisciformes, Pinnipedia) that breed at South Georgia and the South Sandwich Islands, and identified hotspots for their conservation under the recently developed KBA framework. We then evaluated the spatiotemporal overlap of these sites and the different management regimes of krill, demersal longline and pelagic trawl fisheries operating within a large MPA, which was created with the intention to protect marine predator species. Results:We identified 12 new global marine KBAs that are important for this community of top predators, both within and beyond the focal MPA. Only three species consistently used marine areas at a time when a potentially higher-risk fishery was allowed to operate in that area, while other interactions between fisheries and our target species were mostly precluded by MPA management plans. Main conclusions:We show that current fishery management measures within the MPA contribute to protecting top predators considered in this study and that resource harvesting within the MPA does not pose a major threat-under current climate conditions. Unregulated fisheries beyond the MPA, however, pose a likely threat to identified KBAs. Our approach demonstrates the utility of the KBA guidelines and multispecies tracking data to assess the contributing role of well-designed MPAs in achieving local and internationally agreed conservation targets.

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Investigating the responses of marine predators to oceanographic structures is of key importance for understanding their foraging behaviour and reproductive success. Using Global Positioning System (GPS) and Time-Depth-Temperature-Recorder (TDR) tags, we investigated how king penguins breeding at South Georgia explore their foraging area over the summer season in both the horizontal and vertical dimensions. We determined how horizontal habitat use may relate to different Antarctic Circumpolar Current (ACC) frontal zones and associated thermal structuring of the water column. To study the penguins' use of the water column, we examined foraging niches defined by temperature, temperature gradient and depth, and explored the importance of these thermal properties for prey pursuit. King penguins foraged within the Polar Front (PF) and its southern edges during incubation, and the Antarctic Zone (AAZ) and Southern ACC Front (SACCF) during brooding. Foraging niches became more distinct with the advancing summer season, defined by strong thermal gradients at shallow depths in the AAZ, and weak gradients at greater depths in the SACCF. These niches indicate foraging in the sub-thermocline Winter Water (WW) in the AAZ, and in deep WW and Circumpolar Deep Water (CDW) at the SACCF. The influence of different ACC frontal zones in the area to the north of South Georgia appears to provide for a horizontally and vertically segregated environment. The presence of optional foraging areas and niches close to the colony clearly play an important role in these king penguins' foraging success.