Impacts of fisheries and climate on albatross demography

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Climate change and fisheries are major threats to marine biodiversity. Climate influences conditions in the ocean, including levels of primary productivity and acidification, and may eventually affect the routes and strength of ocean currents. This has impacts on the distribution and abundance of organisms at the bottom of food chains, with consequent effects on their predators. Recent research has revealed changes in the extent and duration of winter sea-ice formation in the Antarctic, resulting in a dramatic reduction in Antarctic krill. As this is a key prey for many whales, seals and seabirds, the decline has had adverse effects on their breeding frequency, success and survival.Marine fisheries compete with natural predators and unintentionally catch many non-target (bycatch) species. High bycatch levels have been linked to worldwide declines of seabirds, marine mammals, turtles and sharks. However, fisheries can also bring benefits, as scavengers exploit the fish offal and bycatch discarded by vessels. It is therefore difficult to judge their full impacts without detailed knowledge of the type and extent of interaction. We also need to understand the influence of global climate change, which is predicted to greatly increase the variability and unpredictability of environmental conditions and hence availability of marine resources.Seabirds are major consumers, and as top predators, their populations reflect changes occurring further down food chains, which are in turn influenced by those in the wider environment. Many are threatened, particularly albatrosses which are vulnerable to any unnatural mortality because they fledge one chick only every 1 or 2 years. Given their vast foraging ranges, they overlap with and are killed in multiple fisheries. Recognition of this international problem led to the establishment of a dedicated albatross and petrel conservation agreement (ACAP), ratified by the UK. Seven of the eight albatross populations breeding in the UK Overseas Territories in the South Atlantic are declining (a higher proportion than in any other sector of the Southern Ocean). High bycatch rates are a major contributing factor. Only for black-browed albatross at South Georgia is there evidence of impacts of environmental change; however, there have been no comparable studies of the other species.The wandering, grey-headed and black-browed albatrosses at South Georgia are of global importance, and include two of the five priority populations for conservation identified recently by ACAP. Observed changes in productivity and other population parameters suggest that environmental factors and fisheries affect each species in differing ways, reflecting differences in distribution and life-styles. Studies of seabirds elsewhere have found links between environmental changes and annual variation in breeding success and, in a minority of cases, adult survival, but these depended on the species. Recent modeling carried out on behalf of the Atlantic tuna commission concluded that fisheries are having detrimental impacts on two species from South Georgia, but did not consider grey-headed albatross, nor the implications of changing environmental conditions. There are also two major unresolved issues for these populations, (i) a dramatic drop in survival of chicks from fledging to first return, and (ii) the demographic implications of differing at-sea distributions of males and females, including a sex ratio imbalance if it affects survival.A comprehensive analysis of the contributions of climate and fisheries impacts to differences in survival, breeding frequency and success of these species is not only a high conservation priority, but an outstanding opportunity to improve our understanding of the implications of climatic variation in a region changing at an unprecedented rate. The analysis will provide robust scientific grounds to improve environmental management, particularly at fisheries regulatory bodies