The Southern Ocean is a location where major climate changes occurred over the last century, accompanied with an important level of human exploitation of natural living resources. These global changes can potentially lead to major perturbations of the Southern Ocean ecosystems up to marine top predators. Fisheries may also directly affect seabirds through accidental mortality in fishing gear (bycatch) and additional food resources provided by discards. The past 20 yr of research has seen an increasing number of studies investigating the effects of climate change and fisheries activities on Southern Ocean seabirds. Long-term data of at sea observations and of populations with individually known animals were essential to detect these effects. Here, we review these studies in order to identify patterns in changes in distribution, phenology, demography and population dynamics in response to changes in climate and fisheries activities. Shifts in distribution and breeding phenology were documented in parallel to increases in sea surface temperatures and changes in sea ice cover in the Southern Indian Ocean. Warm sea surface temperatures seem to mainly negatively affect demographic parameters, although exceptions were found. Variations in sea ice cover affected demographic parameters and population dynamics. Relationships suggest non linear effects, with optimum sea ice cover conditions appearing to be the rule. Fishing efforts were mainly negatively related to survival rates and positively related to breeding success, although the latter only concerns a few species. A few studies show that climate factors and fisheries bycatch may affect simultaneously demographic parameters in a complex way, which can be integrated in population models to predict the impact on populations. Although in seabirds population growth rate is less sensitive to variations in juvenile survival than to variations in adult survival, chronic mortality of immatures due to fisheries may negatively affect populations. Population models also allow one to project population trajectories under future climate conditions. Needed are studies that integrate other environmental factors, other trophic levels, foraging behaviour, climate-fisheries interactions, and the mechanisms underlying phenotypic plasticity such as some pioneering studies conducted in the Northern Hemisphere.
