Climate variability has strong effects on marine ecosystems, with repercussions that range in scale from those that impact individuals to those that impact the entire food web. Climate‐induced changes in the abundance of species in lower trophic levels can cascade up to apex predators by depressing vital rates. However, the characteristics and predictability of predator demographic responses remain largely unexplored. We investigated the detectability, limits, and nonlinearity of changes in Antarctic fur seal pup production at South Georgia over a 20‐year period in response to environmental autocorrelation created by global climate perturbations; these were identified in time series of monthly averaged sea surface temperature (SST). Environmental autocorrelation at South Georgia was evident with frequent SST anomalies between 1990 and 1999, during a decade of warm background (time‐averaged) conditions. SST anomalies were preceded by, and cross‐correlated with, frequent El Niño‐La Niña events between 1987 and 1998, which was also a decade of warm background conditions in the tropical Pacific Ocean. Nonlinear mixed‐effects models indicated that positive anomalies at South Georgia explained extreme reductions in Antarctic fur seal pup production over 20 years of study. Simulated environmental time series suggested that the effect of anomalies on Antarctic fur seals was only detectable within a narrow range of positive SST, regardless of the distribution, variance, and autocorrelation structure in SST; this explained the observed nonlinearity in responses in pup production, which were observed only under persistent high SST levels. Such anomalies at South Georgia were likely associated with low availability of prey, largely krill, which affected Antarctic fur seal females over time scales longer than their breeding cycle. Reductions in Antarctic fur seal pup production could thus be predicted in advance by the detection of large‐scale anomalies, which appeared to be driven by trends in global climate perturbation.

Environmental and anthropogenic factors often drive population declines in top predators, but how their influences may combine remains unclear. Albatrosses are particularly threatened. They breed in fast-changing environments, and their extensive foraging ranges expose them to incidental mortality (bycatch) in multiple fisheries. The albatross community at South Georgia includes globally important populations of three species that have declined by 40–60% over the last 35 years. We used three steps to deeply understand the drivers of such dramatic changes: (i) describe fundamental demographic rates using multievent models, (ii) determine demographic drivers of population growth using matrix models, and (iii) identify environmental and anthropogenic drivers using ANOVAs. Each species was affected by different processes and threats in their foraging areas during the breeding and nonbreeding seasons. There was evidence for two kinds of combined environmental and anthropogenic effects. The first was sequential; in wandering and black-browed albatrosses, high levels of bycatch have reduced juvenile and adult survival, then increased temperature, reduced sea-ice cover, and stronger winds are affecting the population recovery potential. The second was additive; in gray-headed albatrosses, not only did bycatch impact adult survival but also this impact was exacerbated by lower food availability in years following El Niño events. This emphasizes the need for much improved implementation of mitigation measures in fisheries and better enforcement of compliance. We hope our results not only help focus future management actions for these populations but also demonstrate the power of the modelling approach for assessing impacts of environmental and anthropogenic drivers in wild animal populations.

Line-transect estimators were developed to assess abundance of coastal dolphins Tursiops truncatus and Stenella coeruleoalba encountered in low densities during aerial sighting surveys. The analysis improved on conventional approaches by objectively combining data from different species, survey areas and other covariates affecting dolphin delectability. Model selection and multimodel inference allowed robust estimates of precision in accounting for covariate selection uncertainty. These methods were used to estimate bottlenose dolphin abundance in NE Mediterranean waters that included a putative subpopulation in the Balearic Islands. Total abundance was estimated as 7654 (coefficient of variation, CV = 0.47; 95% CI = 1608 to 15 766) and the abundance in inshore waters of the Balearic Islands varied from 727 (CV = 0.47; 95% Cl = 149 to 148 1) dolphins in spring 2002 to 1333 (CV = 0.44; 95% CI = 419 to 2617) dolphins in autumn 2002, with an average estimate of 1030 (CV = 0.35; 95% Cl = 415 to 1849). The results do not support an exclusively coastal Balearic Island subpopulation, but they strongly indicate that the islands contain critical habitats required for the conservation of the species. Given the observed decline of the species during the last few decades, conservation-oriented management should focus on reducing or eliminating adverse fishing interactions while key areas are protected from encroachment produced by human development