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International audience; The French Kerguelen Archipelago represents an important breeding place for many species of marine top predators within the Southern Ocean, making the plateau hosting the archipelago and surrounding waters (CCAMLR area 58.5) a crucial area to design conservation measures. In this study, available tracking data from nine species of seabirds and marine mammals breeding at Kerguelen were analysed to define potential boundaries for a Marine Protected Area. Maps of time spent per square of each species were first used to describe high-use areas within the Kerguelen Plateau. Habitat models were then developed for four species (Black-browed albatross, Wandering albatross, King penguin and Antarctic fur seal) chosen on the basis of their contrasted foraging ecology and diet to represent the top predator community. Predictive models were then applied to the main colonies of the four species for which no tracking data were available to illustrate the most important feeding areas at the scale of the entire study zone. An area delineated by the central part of the plateau and its slopes appeared to be of great importance for the top predators’ community and would appropriately complete the limits of the existing Australian marine reserve of Heard and McDonald Islands.

International audience; In tropical waters resources are usually scarce and patchy, and predatory speciesgenerally show specific adaptations for foraging. Tropical seabirds often forage inassociation with sub-surface predators that create feeding opportunities by bringing preyclose to the surface, and the birds often aggregate in large multispecific flocks. Here wehypothesize that frigatebirds, a tropical seabird adapted to foraging with low energeticcosts, could be a good predictor of the distribution of their associated predatory species,including other seabirds (e.g. boobies, terns) and subsurface predators (e.g., dolphins,tunas). To test this hypothesis, we compared distribution patterns of marine predators inthe Mozambique Channel based on a long-term dataset of both vessel- and aerialsurveys, as well as tracking data of frigatebirds. By developing species distributionmodels (SDMs), we identified key marine areas for tropical predators in relation tocontemporaneous oceanographic features to investigate multi-species spatial overlapareas and identify predator hotspots in the Mozambique Channel. SDMs reasonablymatched observed patterns and both static (e.g. bathymetry) and dynamic (e.g.Chlorophyll a concentration and sea surface temperature) factors were importantexplaining predator distribution patterns. We found that the distribution of frigatebirdsincluded the distributions of the associated species. The central part of the channelappeared to be the best habitat for the four groups of species considered in this study(frigatebirds, brown terns, boobies and sub-surface predators).

International audience; We studied the year-round distribution and at-sea activity patterns of the sibling species, northern giant petrel Macronectes halli and southern giant petrel M. giganteus. Loggers combining light-based geolocators and immersion sensors were used to provide year-long data on large-scale distribution and activity of both species from the Crozet Islands (46° 25' S, 51° 51' E) and northern giant petrels from the Kerguelen Islands (49° 19' S, 69° 15' E) in the southern Indian Ocean. Argos platform transmitter terminals (PTTs) were used to track fine-scale movements of breeding adults and juveniles. Overall, adults remained within the Indian Ocean during and outside the breeding season, whereas juveniles dispersed throughout the Southern Ocean. In accordance with previous studies, differences in adult distribution and behaviour were greater between sexes than species: females dispersed more widely than males and also spent more time sitting on the water, particularly during the winter. Observed differences in distribution have important conservation implications: adults, especially males, overlap to a large extent with longline fisheries for Patagonian toothfish Dissostichus eleginoides in shelf areas within national Exclusive Economic Zones (EEZs), whereas adult females and juveniles are more likely to encounter high-sea longline fleets targeting tuna in subtropical waters. The circumpolar wide ranging behavior of naïve juvenile birds makes them particularly susceptible to interaction with a wide range of longline fisheries.