Impacts of fisheries and climate on albatross demography

气候变化和渔业是对海洋生物多样性的主要威胁。气候影响海洋状况，包括初级生产力水平和酸化程度，并可能最终影响洋流的路线和强度。这对食物链底部的生物体的分布和丰度产生了影响，从而对它们的捕食者产生了影响。最近的研究表明，南极冬季海冰形成的范围和持续时间发生了变化，导致南极磷虾数量急剧减少。由于这是许多鲸鱼、海豹和海鸟的主要猎物，这种下降对它们的繁殖频率、成功和生存产生了不利影响。海洋渔业与自然捕食者竞争，无意中捕获了许多非目标(副渔获物)物种。高副渔获物水平与全球海鸟、海洋哺乳动物、海龟和鲨鱼的减少有关。然而，渔业也可以带来好处，因为清道夫利用船只丢弃的鱼类内脏和副渔获物。因此，在不详细了解相互作用的类型和程度的情况下，很难判断其全部影响。我们还需要了解全球气候变化的影响，预计这将大大增加环境条件的变异性和不可预测性，从而增加海洋资源的可获得性。海鸟是主要的消费者，作为顶级捕食者，它们的种群反映了食物链下游发生的变化，而这些变化反过来又受到更广泛环境中的变化的影响。许多都受到了威胁，特别是信天翁，它们很容易受到任何非自然死亡的影响，因为它们每1到2年才产下一只雏鸟。鉴于它们广阔的觅食范围，它们与多个渔业重叠，并在多个渔业中被捕杀。认识到这一国际问题导致了专门的信天翁和海燕保护协议(ACAP)的建立，并得到了英国的批准。在南大西洋英国海外领土繁殖的8个信天翁种群中，有7个种群正在下降(这一比例高于南大洋任何其他地区)。高副渔获率是一个主要的促成因素。只有南乔治亚州的黑眉信天翁有证据表明环境变化的影响；然而，还没有对其他物种进行类似的研究。南乔治亚州漂泊的、灰头和黑眉信天翁具有全球重要性，包括ACAP最近确定的五个优先保护种群中的两个。观察到的生产力和其他种群参数的变化表明，环境因素和渔业以不同的方式影响每个物种，反映了分布和生活方式的差异。其他地方对海鸟的研究发现，环境变化与繁殖成功率的年度变化之间存在联系，在少数情况下，成年海鸟的存活也与环境变化有关，但这取决于物种。最近代表大西洋金枪鱼委员会进行的建模得出结论，渔业正在对南乔治亚州的两个物种产生有害影响，但没有考虑灰头信天翁，也没有考虑环境条件变化的影响。对于这些种群来说，还有两个主要的悬而未决的问题，(I)幼鸟从羽化到首次返回的存活率急剧下降，(Ii)雄性和雌性在海上的不同分布对人口统计学的影响，包括性别比例失衡，如果它影响到生存的话。全面分析气候和渔业影响对这些物种的生存、繁殖频率和成功的影响的贡献，不仅是一个高度优先的保护优先事项，而且是一个极好的机会，可以增进我们对气候变化在一个以前所未有的速度变化的区域的影响的理解。这一分析将为改善环境管理，特别是渔业监管机构的环境管理提供强有力的科学依据。

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