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Incidental mortality (bycatch) in fisheries remains the greatest threat to many large marine vertebrates and is a major barrier to fisheries sustainability. Robust assessments of bycatch risk are crucial for informing effective mitigation strategies, but are hampered by missing information on the distributions of key life‐history stages (adult breeders and non‐breeders, immatures and juveniles). Using a comprehensive biologging dataset (1,692 tracks, 788 individuals) spanning all major life‐history stages, we assessed spatial overlap of four threatened seabird populations from South Georgia, with longline and trawl fisheries in the Southern Ocean. We generated monthly population‐level distributions, weighting each life‐history stage according to population age structure based on demographic models. Specifically, we determined where and when birds were at greatest potential bycatch risk, and from which fleets. Overlap with both pelagic and demersal longline fisheries was highest for black‐browed albatrosses, then white‐chinned petrels, wandering and grey‐headed albatrosses, whereas overlap with trawl fisheries was highest for white‐chinned petrels. Hotspots of fisheries overlap occurred in all major ocean basins, but particularly the south‐east and south‐west Atlantic Ocean (longline and trawl) and south‐west Indian Ocean (pelagic longline). Overlap was greatest with pelagic longline fleets in May–September, when fishing effort south of 25°S is highest, and with demersal and trawl fisheries in January–June. Overlap scores were dominated by particular fleets: pelagic longline—Japan, Taiwan; demersal longline and trawl—Argentina, Namibia, Falklands, South Africa; demersal longline—Convention for Conservation of Antarctic Marine Living Resources (CCAMLR) waters, Chile, New Zealand. Synthesis and applications. We provide a framework for calculating appropriately weighted population‐level distributions from biologging data, which we recommend for future fisheries bycatch risk assessments. Many regions of high spatial overlap corresponded with high seabird bycatch rates recorded by on‐board observers, indicating that our approach reliably mapped relative bycatch risk at large spatial scales. Implementation of effective bycatch mitigation in these high‐risk regions varies considerably. Although potential bycatch risk appears to have decreased since the early 2000s, albatross and petrel populations from South Georgia and elsewhere are still declining, emphasizing the need for much improved observer coverage and monitoring of compliance with bycatch regulations. 摘要 漁業活動中的意外捕獲(bycatch)造成許多海洋脊椎動物嚴重的生存威脅，意外捕獲也是漁業永續經營的主要障礙。而對意外捕獲風險做出可靠的風險評估，對於提出有效的忌避策略至關重要，然而卻受限於缺少這些受脅物種生活史各個關鍵階段(繁殖期成鳥、非繁殖成鳥、亞成鳥、幼鳥)的分布資料。 使用獨特的全面生物資料輸入數據組(1697項追蹤、790個體)，資料涵蓋了生活史各個主要階段，我們評估了在南喬治亞4種受脅海鳥族群範圍，與在南冰洋的延繩釣及拖繩漁業作業範圍的重疊情形。將資料套用族群模式推估出族群年齡結構，再將生活史各階段賦予權重，我們製作了每月族群分布圖。我們更針對性指出特定海鳥在那一個季節、那一個海域受到意外捕獲的最高風險，以及是被那一類漁船所威脅。 與浮延繩釣及底延繩釣作業區域重疊最高的是黑眉信天翁，其次為白額鸌、漂泊信天翁、灰頭信天翁。與拖繩漁業區域重疊最高的是白額鸌。 海鳥族群與漁業重疊熱點發生在所有主要的海盆，特別是在大西洋的西南部及東南部（延繩釣及拖網漁業），印度洋西南（浮延繩釣漁業）。對於遠洋浮延繩釣船隊而言重疊度最高是在5月至9月，這時在南緯25度以南的漁業作業最頻繁，底延繩釣及拖網漁業高峰則在1月至6月。重疊指數被特定船隊所主導: 浮延繩釣為日本及臺灣; 底延繩釣及拖網為阿根廷、納米比亞、福克蘭、南非；CCAMLR海域的底延繩釣為智利、紐西蘭。 綜合及應用：我們提供了一個架構可以用生物資訊輸入數據，計算經合理權重後的族群分布，我們建議未來可應用於意外捕獲風險評估。許多高度重疊區域呼應了由隨船觀察員紀錄的高海鳥意外捕獲率，顯示出我們這個方法可製作可信度高的意外捕獲風險地圖。在這些高風險區域安排有效海鳥忌避措施的作法有相當大的差異。雖然自2000年初以來，潛在意外捕獲風險看似降低，但南喬治亞及其它地區的信天翁及水薙鳥的族群數量仍在下降，更突顯出需要改進意外捕獲規定中觀察員覆蓋度，以及改善監測漁船忌避措施規定的遵守。 要旨 漁業による偶発的な死（混獲）は未だに多くの大型海洋性脊椎動物にとって最大の脅威であり、持続可能な漁業の障害となっている。効果的な対策には頑健な混獲リスク評価が重要だが、生活環のステージごと（繁殖成体、非繁殖成体、幼体、亜成体）の分布情報の不足が妨げとなっている。 全ての主な生活環のステージを含む包括的なバイオロギングデータ（1697追跡、790個体）をもとに、サウスジョージアに生息する海鳥4種の絶滅危惧個体群と、南氷洋の延縄漁とトロール漁の空間的重複を評価した。月毎の海鳥個体群レベルの分布域の作成には、個体群統計モデルをもとに各生活環ステージの年齢構成を考慮した。特に、何時、何処で、どの船団によって海鳥が混獲リスクに晒される可能性が高いかを判定した。 浮延縄漁と底延縄漁との重複はマユグロアホウドリが最も高く、ノドジロクロミズナギドリ、ワタリアホウドリ、ハイガシラアホウドリが次いだ。トロール漁と の重複はノドジロクロミズナギドリが最も高かった。 漁業との重複が高いホットスポットは全ての主要海盆で判明したが、特に大西洋の南東域と南西域（延縄とトロール）、インド洋の南西域（浮延縄）で高かった。重複が最も高かったのは、浮延縄では南緯25度以南の漁獲努力量が最も高い5月から9月で、底延縄とトロールでは1月から6月であった。顕著に重複スコアが高かった特定の船団は以下のとおりであった：浮延縄 ‐日本、台湾；底延縄とトロール ‐ アルゼンチン、ナミビア、フォークランド諸島、南アフリカ；底延縄 ‐ CCAMLR海域、チリ、ニュージーランド。 総括と適用。今後の漁業による混獲リスク評価には、ここに示したようにバイオロギングデータをもとにした、また適切な考慮を含む、個体群レベルの分布計算の枠組みを推奨する。空間的重複が高いと推定された多くの海域では科学オブザーバーによっても高い混獲率が記録されており、この手法で混獲リスクを大きな空間スケールで的確にマッピングができることが示された。効果的な混獲対策の施行は、リスクの高い海域間で大きく異なっている。2000年代前半以降は潜在的な混獲リスクが減少したように見受けられるが、サウスジョージアやその他のアホウドリ類とミズナギドリ類の個体数は未だに減少しており、科学オブザーバーによるカバー率と混獲に関する規制順守のモニタリングの大幅な改善の必要性を強調する。 We provide a framework for calculating appropriately weighted population‐level distributions from biologging data, which we recommend for future fisheries bycatch risk assessments. Many regions of high spatial overlap corresponded with high seabird bycatch rates recorded by on‐board observers, indicating that our approach reliably mapped relative bycatch risk at large spatial scales. Implementation of effective bycatch mitigation in these high‐risk regions varies considerably. Although potential bycatch risk appears to have decreased since the early 2000s, albatross and petrel populations from South Georgia and elsewhere are still declining, emphasizing the need for much improved observer coverage and monitoring of compliance with bycatch regulations.

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.

Climate changes include concurrent changes in environmental mean, variance and extremes, and it is challenging to understand their respective impact on wild populations, especially when contrasted age-dependent responses to climate occur. We assessed how changes in mean and standard deviation of sea surface temperature (SST), frequency and magnitude of warm SST extreme climatic events (ECE) influenced the stochastic population growth rate log(λs) and age structure of a black-browed albatross population. For changes in SST around historical levels observed since 1982, changes in standard deviation had a larger (threefold) and negative impact on log(λs) compared to changes in mean. By contrast, the mean had a positive impact on log(λs). The historical SST mean was lower than the optimal SST value for which log(λs) was maximized. Thus, a larger environmental mean increased the occurrence of SST close to this optimum that buffered the negative effect of ECE. This ‘climate safety margin’ (i.e. difference between optimal and historical climatic conditions) and the specific shape of the population growth rate response to climate for a species determine how ECE affect the population. For a wider range in SST, both the mean and standard deviation had negative impact on log(λs), with changes in the mean having a greater effect than the standard deviation. Furthermore, around SST historical levels increases in either mean or standard deviation of the SST distribution led to a younger population, with potentially important conservation implications for black-browed albatrosses. This article is part of the themed issue ‘Behavioural, ecological and evolutionary responses to extreme climatic events’.

Many animal taxa exhibit sex‐specific variation in ecological traits, such as foraging and distribution. These differences could result in sex‐specific responses to change, but such demographic effects are poorly understood. Here, we test for sex‐specific differences in the demography of northern (NGP, Macronectes halli) and southern (SGP, M. giganteus) giant petrels – strongly sexually size‐dimorphic birds that breed sympatrically at South Georgia, South Atlantic Ocean. Both species feed at sea or on carrion on land, but larger males (30% heavier) are more reliant on terrestrial foraging than the more pelagic females. Using multi‐event mark‐recapture models, we examine the impacts of long‐term changes in environmental conditions and commercial fishing on annual adult survival and use two‐sex matrix population models to forecast future trends. As expected, survival of male NGP was positively affected by carrion availability, but negatively affected by zonal winds. Female survival was positively affected by meridional winds and El Niño–Southern Oscillation (ENSO), and negatively affected by sea ice concentration and pelagic longline effort. Survival of SGPs did not differ between sexes; however, survival of males only was positively correlated with the Southern Annular Mode (SAM). Two‐sex population projections indicate that future environmental conditions are likely to benefit giant petrels. However, any potential increase in pelagic longline fisheries could reduce female survival and population growth. Our study reveals that sex‐specific ecological differences can lead to divergent responses to environmental drivers (i.e. climate and fisheries). Moreover, because such effects may not be apparent when all individuals are considered together, ignoring sex differences could underestimate the relative influence of a changing environment on demography. Giant petrels (Macronectes spp.) are the most sexually size‐dimorphic of all seabirds. The author's study reveals that the resulted sex‐specific ecological differences can lead to divergent responses to environmental drivers. Moreover, because such effects may not be apparent when all individuals are considered together, ignoring sex differences could underestimate the relative influence of a changing environment on demography.

In long-lived species only a fraction of a population breeds at a given time. Non-breeders can represent more than half of adult individuals, calling in doubt the relevance of estimating demographic parameters from the sole breeders. Here we demonstrate the importance of considering observable non-breeders to estimate reliable demographic traits: survival, return, breeding, hatching and fledging probabilities. We study the long-lived quasi-biennial breeding wandering albatross (Diomedea exulans). In this species, the breeding cycle lasts almost a year and birds that succeed a given year tend to skip the next breeding occasion while birds that fail tend to breed again the following year. Most non-breeders remain unobservable at sea, but still a substantial number of observable non-breeders (ONB) was identified on breeding sites. Using multi-state capture-mark-recapture analyses, we used several measures to compare the performance of demographic estimates between models incorporating or ignoring ONB: bias (difference in mean), precision (difference is standard deviation) and accuracy (both differences in mean and standard deviation). Our results highlight that ignoring ONB leads to bias and loss of accuracy on breeding probability and survival estimates. These effects are even stronger when studied in an age-dependent framework. Biases on breeding probabilities and survival increased with age leading to overestimation of survival at old age and thus actuarial senescence and underestimation of reproductive senescence. We believe our study sheds new light on the difficulties of estimating demographic parameters in species/taxa where a significant part of the population does not breed every year. Taking into account ONB appeared important to improve demographic parameter estimates, models of population dynamics and evolutionary conclusions regarding senescence within and across taxa.

Theoretical and empirical studies have highlighted the effects of age on several life-history traits in wild populations. There is also increasing evidence for environmental effects on their demographic traits. However, quantifying how individuals differentially respond to environmental variations according to their age remains a challenge in ecology. In a population of Black-browed Albatrosses monitored during 43 years, we analyzed how life-history traits varied according to age, and whether individuals of different ages responded in different ways to environmental conditions. To do so, we: (1) examined how age affected seven life-history traits, (2) investigated differences in temporal variance of demographic traits between age classes, and (3) tested for age-dependent effects of climate and fisheries covariates on demographic traits. Overall, there was a tendency for traits to improve during the first years of life (5-10 years), to peak and remain stable at middle age (10-30 years), and decline at old ages. At young ages, survival and reproductive parameters increased, except offspring body condition at fledging, suggesting that younger parents had already acquired good foraging capacities. However, they suffered from inexperience in breeding as suggested by their higher breeding failures during incubation. There was evidence for reproductive and actuarial senescence. In particular, breeding success and offspring body condition declined abruptly, suggesting altered foraging capacities of old individuals. Middle-aged individuals had the lowest temporal variance of demographic traits. Although this is predicted by the theory of environmental canalization, it could also results from a higher susceptibility of young and old birds due to their respective inexperience and senescence. The highest temporal variances were found in old individuals. Survival was significantly influenced by sea surface temperatures in the foraging zone of this albatross population during breeding. During warm events survival of young and old individuals improved, whereas a decrease was observed for middle-aged individuals. Presumably, during cold years with poor environmental conditions, young and old breeding birds may suffer more from intraspecific competition for resources than middle-aged individuals. This study showed that age, known as a major factor structuring demography in long-lived species, can also potentially influence the response of populations to global change.

Climate change, fisheries and invasive species represent three pervasive threats to seabirds, globally. Understanding the relative influence and compounding nature of marine and terrestrial threats on the demography of seabird communities is vital for evidence-based conservation. Using 20 years of capture-mark-recapture data from four sympatric species of albatross (black-browed Thalassarche melanophris , gray-headed T. chrysostoma , light-mantled Phoebetria palpebrata and wandering Diomedea exulans ) at subantarctic Macquarie Island, we quantified the temporal variability in survival, breeding probability and success. In three species (excluding the wandering albatross because of their small population), we also assessed the influence of fisheries, oceanographic and terrestrial change on these rates. The Southern Annular Mode (SAM) explained 20.87–29.38% of the temporal variability in survival in all three species and 22.72–28.60% in breeding success for black-browed and gray-headed albatross, with positive SAM events related to higher success. The El Niño Southern Oscillation (ENSO) Index explained 21.14–44.04% of the variability in survival, with higher survival rates following La Niña events. For black-browed albatrosses, effort in south-west Atlantic longline fisheries had a negative relationship with survival and explained 22.75–32.21% of the variability. Whereas increased effort in New Zealand trawl fisheries were related to increases in survival, explaining 21.26–28.29 % of variability. The inclusion of terrestrial covariates, reflecting extreme rainfall events and rabbit-driven habitat degradation, explained greater variability in trends breeding probability than oceanographic or fisheries covariates for all three species. These results indicate managing drivers of demographic trends that are most easily controlled, such as fisheries and habitat degradation, will be a viable option for some species (e.g., black-browed albatross) but less effective for others (e.g., light-mantled albatross). Our results illustrate the need to integrate fisheries, oceanographic and terrestrial processes when assessing demographic variability and formulating the appropriate management response.

Individual heterogeneity in foraging behavior has been widely documented within predator populations. In highly social apex predators such as killer whales ( Orcinus orca ), specialization may occur at the matriline level. A small population of killer whales has been documented to occur around the Crozet Islands. These whales feed on a wide range of prey items including seals, penguins and large whales, as well as depredate the local Patagonian toothfish ( Dissostichus eleginoides ) longline fishery. The level of interactions with fisheries varies greatly between matrilines. Here, we present the results on the effects of such behavioral heterogeneity on the demographic trends of this killer whale population. We used photo-identification data from 1977 to 2011 in a mark–recapture framework to test the effect of varying levels of fisheries interactions on adult survival. We documented significant differences in survival between depredating and non-depredating whales, resulting in divergent intra-population demographic trends. These differences showed low survival, and thus a negative effect, for depredating whales when illegal fishing occurred (poachers used lethal methods to deter killer whales from depredating longlines). After illegal fishing stopped (2003–2011), the survival rates of depredating individuals exceeded the survival rates of non-depredating individuals, suggesting a positive influence of “artificial food provisioning”. This effect was further supported by a higher population growth rate for depredating whales. This study highlights the potential demographic costs and benefits that cetaceans face from depredating fisheries and addresses the demographic consequences of both intra-population feeding specialization and the influence of anthropogenic changes in resource availability.

The canalization hypothesis postulates that the rate at which trait variation generates variation in the average individual fitness in a population determines how buffered traits are against environmental and genetic factors. The ranking of a species on the slow-fast continuum - the covariation among life-history traits describing species-specific life cycles along a gradient going from a long life, slow maturity, and low annual reproductive output to a short life, fast maturity, and high annual reproductive output - strongly correlates with the relative fitness impact of a given amount of variation in adult survival. Under the canalization hypothesis, longlived species are thus expected to display less individual heterogeneity in survival at the onset of adulthood, when reproductive values peak, than short-lived species. We tested this life-history prediction by analysing long-term time series of individual-based data in nine species of birds and mammals using capture-recapture models. We found that individual heterogeneity in survival was higher in species with short-generation time (< 3 years) than in species with long generation time (> 4 years). Our findings provide the first piece of empirical evidence for the canalization hypothesis at the individual level from the wild.

Sex differences in lifespan and aging are wide-spread among animals. Since investment in current reproduction can have consequences on other life-history traits, the sex with the highest cost of breeding is expected to suffer from an earlier and/or stronger senescence. This has been demonstrated in polygynous species that are highly dimorphic. However in monogamous species where parental investment is similar between sexes, sex-specific differences in aging patterns of life-history traits are expected to be attenuated. Here, we examined sex and age influences on demographic traits in a very long-lived and sexually dimorphic monogamous species, the wandering albatross (Diomedea exulans). We modelled within the same model framework sex-dependent variations in aging for an array of five life-history traits: adult survival, probability of returning to the breeding colony, probability of breeding and two measures of breeding success (hatching and fledging). We show that life-history traits presented contrasted aging patterns according to sex whereas traits were all similar at young ages. Both sexes exhibited actuarial and reproductive senescence, but, as the decrease in breeding success remained similar for males and females, the survival and breeding probabilities of males were significantly more affected than females. We discuss our results in the light of the costs associated to reproduction, age-related pairing and a biased operational sex-ratio in the population leading to a pool of non-breeders of potentially lower quality and therefore more subject to death or breeding abstention. For a monogamous species with similar parental roles, the patterns observed were surprising and when placed in a gradient of observed age/sex-related variations in life-history traits, wandering albatrosses were intermediate between highly dimorphic polygynous and most monogamous species.