The Antarctic seasonal sea-ice zone (SIZ) is one of the most extensive and dynamic habitats on Earth. In summer, increased insolation and ice melt cause primary production to peak, sustaining large populations of locally-breeding seabirds. Due to their hypermobility, large Procellariiformes, including albatrosses, breeding in the subantarctic also have the potential to access the SIZ and track macroscale resource waves over the Sothern Ocean but the extent to which they do this is poorly known. Here, we analysed the foraging movements of breeding albatrosses and large petrels (seven species, 1298 individuals) recorded using GPS loggers and satellite-transmitters to quantify their use of sea-ice habitats and test whether they tracked seasonal drivers of primary production. Foraging latitudes of white-chinned petrels Procellaria aequinoctialis and black-browed Thalassarche melanophris, grey-headed T. chrysostoma and wandering albatrosses Diomedea exulans varied sinusoidally over the breeding season, presumably in response to lagged effects of solar irradiance on primary production. Foraging latitudes of northern and southern giant petrels (Macronectes halli and M. giganteus), and light-mantled albatrosses Phoebetria palpebrata, exhibited no strong seasonal trend, but the latter two species spent ≥ 20 % of their time in the SIZ during incubation and post-brood, prior to or at the time of the spring ice breakup. Southern giant petrels travelled 100 s of km into the pack ice, encountering sea-ice concentrations up to 100 %, whereas light-mantled albatrosses remained almost exclusively in open water near the Marginal Ice Zone (MIZ). The remaining species spent up to 15 % of their time in the SIZ, typically from 5-7 weeks after breakup, and avoided the MIZ. This supports hypotheses that sea ice presents albatrosses but not giant petrels with physical barriers to flight or foraging, and that open-water-affiliated species use the SIZ only after primary production stimulated by ice melt transfers to intermediate trophic levels. Given that all seven species used the SIZ, it is likely that the phenology and demography of these and many other subantarctic-breeding seabirds are mechanistically linked to sea-ice dynamics. Declines in Antarctic sea ice predicted under climate change could therefore modulate and exacerbate the already unsustainable anthropogenic impacts being experienced by these populations.

The BirdLife Seabird Tracking Database (STDB) was established in 2004 to collate tracking data to address the incidental mortality of seabirds in fisheries and to contribute to identification of sites at sea relevant to establishment of Marine Protected Areas. After 20 years, the STDB has grown to hold ca. 39 million locations for 168 species from >450 breeding sites. The STDB has become a powerful tool to support marine conservation by facilitating the compilation of robust multi-species data to address broad-scale questions, made possible by continuous collaboration with the scientific community. The STDB has facilitated major marine conservation outcomes, including the designation of the first marine protected area to be identified solely using tracking data. Advocacy based on analyses demonstrating overlaps between seabirds and fisheries have led to the adoption of seabird-bycatch mitigation measures by Regional Fisheries Management Organizations. The STDB has also provided compelling evidence for migratory connectivity in the ocean, and been crucial in informing many policy instruments at scales from national (e.g. protection and management of important sites identified from tracking data), to regional (e.g. working with Regional Conventions), to global (e.g. the identification of Ecologically or Biologically Significant Marine Areas). This review presents an overview of 1) how the STDB started and gained traction, 2) its current status in terms of data coverage and gaps, 3) methodological developments, 4) conservation successes, 5) the opportunities and challenges experienced in managing this global database, and 6) research priorities and future directions for seabird tracking studies.

Summary Frigatebirds have been in taxonomic oblivion for nearly a century. A new genetic study by Martins et al. (2022) provides a stimulus and potential basis for a long-overdue modern review, which might lead to recognition of up to five new species-level taxa, two of which would be “Critically Endangered” globally and may already be effectively extinct. Even some of the more widespread frigatebird taxa are subject to multiple anthropogenic threats and, outside strictly protected and managed areas, may already be in serious decline. Seabird experts and organisations need urgently to review all available data relevant to frigatebird taxonomy and populations, collect additional material for genetic analysis, undertake new assessments of conservation status, and (in collaboration with appropriate regulatory authorities) propose and execute appropriate conservation and management actions.

We present the first objective quantitative assessment of the threats to all 359 species of seabirds, identify the main challenges facing them, and outline priority actions for their conservation. We applied the standardised Threats Classification Scheme developed for the IUCN Red List to objectively assess threats to each species and analysed the data according to global IUCN threat status, taxonomic group, and primary foraging habitat (coastal or pelagic). The top three threats to seabirds in terms of number of species affected and average impact are: invasive alien species, affecting 165 species across all the most threatened groups; bycatch in fisheries, affecting fewer species (100) but with the greatest average impact; and climate change/severe weather, affecting 96 species. Overfishing, hunting/trapping and disturbance were also identified as major threats to seabirds. Reversing the top three threats alone would benefit two-thirds of all species and c. 380 million individual seabirds (c. 45% of the total global seabird population). Most seabirds (c. 70%), especially globally threatened species, face multiple threats. For albatrosses, petrels and penguins in particular (the three most threatened groups of seabirds), it is essential to tackle both terrestrial and marine threats to reverse declines. As the negative effects of climate change are harder to mitigate, it is vital to compensate by addressing other major threats that often affect the same species, such as invasive alien species, bycatch and overfishing, for which proven solutions exist.

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 degrees 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.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Marine Spatial Planning (MSP) is becoming a key management approach throughout the world. The process includes the mapping of how humans and wildlife use the marine environment to inform the development of management measures. An integrated multi-species approach to identifying key areas is important for MSP because it allows managers a global representation of an area, enabling them to see where management can have the most impact for biodiversity protection. However, multi-species analysis remains challenging. This paper presents a methodological framework for mapping key areas for marine megafauna (seabirds, pinnipeds, cetaceans) by incorporating different data types across multiple species. The framework includes analyses of tracking data and observation survey data, applying analytical steps according to the type of data available during each year quarter for each species. It produces core-use area layers at the species level, then combines these layers to create megafauna core-use area layers. The framework was applied in the Falkland Islands. The study gathered over 750,000 tracking and at-sea observation locations covering an equivalent of 5495 data days between 1998 and 2015 for 36 species. The framework provides a step-by-step implementation protocol, replicable across geographic scales and transferable to multiple taxa. R scripts are provided. Common repositories, such as the Birdlife International Tracking Database, are invaluable tools, providing a secure platform for storing and accessing spatial data to apply the methodological framework. This provides managers with data necessary to enhance MSP efforts and marine conservation worldwide.

Knowing the spatial scales at which effective management can be implemented is fundamental for conservation planning. This is especially important for mobile species, which can be exposed to threats across large areas, but the space use requirements of different species can vary to an extent that might render some management approaches inefficient. Here the space use patterns of seabirds were examined to provide guidance on whether conservation management approaches should be tailored for taxonomic groups with different movement characteristics. Seabird tracking data were synthesised from 5419 adult breeding individuals of 52 species in ten families that were collected in the Atlantic Ocean basin between 1998 and 2017. Two key aspects of spatial distribution were quantified, namely how far seabirds ranged from their colony, and to what extent individuals from the same colony used the same areas at sea. There was evidence for substantial differences in patterns of space-use among the ten studied seabird families, indicating that several alternative conservation management approaches are needed. Several species exhibited large foraging ranges and little aggregation at sea, indicating that area-based conservation solutions would have to be extremely large to adequately protect such species. The results highlight that short-ranging and aggregating species such as cormorants, auks, some penguins, and gulls would benefit from conservation approaches at relatively small spatial scales during their breeding season. However, improved regulation of fisheries, bycatch, pollution and other threats over large spatial scales will be needed for wide-ranging and dispersed species such as albatrosses, petrels, storm petrels and frigatebirds.

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.

Many animals partition resources to avoid competition, and in colonially-breeding species this often leads to divergent space or habitat use. During the non-breeding season, foraging constraints are relaxed, yet the patterns and drivers of segregation both between and within populations are poorly understood. We modelled habitat preference to examine how extrinsic (habitat availability and intra-specific competition) and intrinsic factors (population, sex and breeding outcome) influence the distributions of non-breeding grey-headed albatrosses Thalassarche chrysostoma tracked from two major populations, South Georgia (Atlantic Ocean) and the Prince Edward Islands (Indian Ocean). Spatial segregation was greater than expected, reflecting distinct seasonal differences in habitat selection and accessibility, and avoidance of intra-specific competition with local breeders. Previously failed birds segregated spatially from successful birds during summer, when they used less productive waters, suggesting a link between breeding outcome and subsequent habitat selection. In contrast, we found weak evidence of sexual segregation, which did not reflect a difference in habitat use. Our results indicate that the large-scale spatial structuring of albatross distributions results from interactions between extrinsic and intrinsic factors, with important implications for population dynamics. As habitat preferences differed substantially between colonies, populations should be considered independently when identifying critical areas for protection.

John Croxall has had a long and distinguished association with the BOU. He joined as a student (and still a teenager) in 1965, becoming a Council member during 1974–78, and then serving as Vice President during 1987–91 and as President during 1995–99. During his time as President, John was responsible for one of the most significant developments ever for the BOU; appointing a full-time Administrator, Steve Dudley, when the then long-serving, part-time secretary, Gwen Bonham, chose to retire. The decision to invest more of the Union's resources in securing its long-term administration provided the platform on which all subsequent development of the BOU has been founded, and John's recognition of the need for this restructuring has therefore been a key component of the Union's continued success. John's career has been distinguished, with most people knowing him through his work on the marine birds and mammals of the Southern Ocean and Antarctica, and others through his tireless work on committees and working groups. He was educated at King Edward's School in Birmingham and Queen's College Oxford, leading to a first-class degree in zoology, followed by a PhD at the University of Auckland. After returning to Britain, he took up a short-term position as Research Associate at the University of Newcastle-upon-Tyne (1972–75), studying the problems of oiling in seabirds, an issue of great conservation concern at the time. He then moved to the British Antarctic Survey (BAS), where for the next 30 years he directed bird and mammal research, occupying progressively higher positions in this organization until his retirement as Head of Conservation Biology in 2006. While at BAS, John's main work focused on the role of sea birds and mammals as predators of other marine life, and their significance in the nutrient flux of the Southern Ocean. He helped to develop and use new ways of studying the diets, movements and energetics of ocean-living animals during swimming, diving and flight. He developed the first realistic models of the important krill-based predator–prey interactions in the Southern Ocean, which subsequently proved important in the sustainable development of southern fisheries. He also initiated the collection of co-ordinated long-term data on the dynamics of Southern Ocean top predators, including international programmes to map, by remote tracking, the core distributions and migration routes of albatrosses. His approach was based on high-quality personal research and perceptive syntheses of relevant literature, revealing a firm grasp of the underlying science. Another major research contribution concerned the life-history strategies of marine birds and mammals, with studies of the age of first breeding, age-related survival and reproductive success. He was concerned particularly with albatrosses, which, being some of the longest-lived and slowest-reproducing of birds, gave his work a special interest and significance. It was partly this work that, from annual survival estimates, revealed the slow long-term decline in albatross populations, attributed to the extra mortality imposed by long-line fisheries practices. His work on the demography and population sizes of various Southern Ocean birds and mammals has also provided a firm basis for the assessment of the effects of climate change and other human impacts on Antarctic wildlife. In these ways, he contributed not only to Antarctic ecology, but more widely to prevailing areas of debate in ecology and conservation. His publication record is also outstanding, amounting to around 320 papers and book chapters, and in a more popular vein, the Field Guide to the Wildlife of South Georgia (2012). However, his contribution has extended well beyond relevant research, as he has ensured that research findings have been applied to the sustainable use and conservation of Antarctic ecosystems. He has, for example, been a leading member of the UK delegation to the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR). He has been centrally involved in the UK's attempts to develop a coherent strategy for the management and conservation of these resources, and is a principal architect of the region's fisheries management policy. He also led global initiatives to manage Southern Ocean fisheries so as to minimize by-catch, especially of albatrosses. In addition to his work in the Southern Ocean, John has also contributed in a voluntary capacity to the development of conservation in Britain, mainly from his work, over 14 years, on the Council of the RSPB. He was involved first as a Council Member, then as Chairman of the Conservation Committee, and finally as Chairman of Council (1998–2003). In the latter role particularly, John's balance, tact and diplomacy contributed greatly to the development of the Society's conservation strategy at the time, and to its all-important relationships with its members, with other conservation organizations and with relevant sectors of Government. After his retirement from BAS, John became chair of Birdlife International's Global Seabird Programme in 2006, with responsibility for developing and implementing strategies for improving the conservation status of seabirds worldwide, a position which he holds to the present day. He was also a member of the Permanent Executive of the International Ornithological Committee during 1998–2006, and a founding Trustee of both Falklands Conservation (which he chaired during 1993–98) and the South Georgia Heritage Trust (where he plays a major role in the rodent eradication programme). These are just some of the voluntary ornithological and conservation organizations in which John has played an active role. The strength of his personal contributions to bird science and conservation have been internationally recognized by a string of prestigious awards, including the Scientific Medal of the Zoological Society (1984), the Polar Medal (1992 and 2004), the President's Medal of the British Ecological Society (1995), the Robert Cushman Murphy Medal of the International Colonial Waterbird Society (1997), the Marsh Award for Conservation of the Zoological Society of London (2002), the Godman-Salvin Medal of the British Ornithologists’ Union (2004), and the Lifetime Achievement Award of the Pacific Seabird Group (2008). He received honorary professorships from the Universities of Birmingham (1998) and Durham (1998), and an Honorary Fellowship of the AOU in 2004. On the basis of his research, he was elected Fellow of the Royal Society in 2005, in recognition of ‘his pioneering work with marine mammals and seabirds, particularly albatrosses, and his role in applying scientific research in the fields of conservation and fisheries management’. His wider contribution to research and conservation was recognized by the award of a CBE in 2004. In terms of his personal research, his commitment and influence, and his wider international contribution to conservation and resource management, as well as his commitment to the development of the BOU, John Croxall is an exemplary citizen of his discipline. For these various reasons, he is a well-deserving recipient of the BOU's Union Medal.

The mountainous island of South Georgia, situated in the cold but productive waters of the Southern Ocean, is one of the world’s most important seabird islands. It is estimated that over 100 million individual seabirds are based there, and that there may have been an order of magnitude more before the introduction of rats. South Georgia has 29 species of breeding bird, and is the world’s most important breeding site for six species (Macaroni Penguin Eudyptes chrysolophus, Grey-headed Albatross Thalassarche chrysostoma, Northern Giant Petrel Macronectes halli, Antarctic Prion Pachyptila desolata, White-chinned Petrel Procellaria aequinoctialis and Common Diving Petrel Pelecanoides urinatrix). It is also probably in the top three such sites for seven others (King Penguin Aptenodytes patagonicus, Gentoo Penguin Pygoscelis papua, Wandering Albatross Diomedea exulans, Black-browed Albatross Thalassarche melanophris, Southern Giant Petrel Macronectes giganteus, Black-bellied Storm-petrel Fregetta tropica and South Georgia Diving Petrel Pelecanoides georgicus). Several of these species are globally threatened or near-threatened, which enhances the importance of South Georgia and emphasises the need for action to improve the conservation status of its birds. Although South Georgia is currently classified by BirdLife International as a single Important Bird Area (IBA), closer scrutiny may well reveal that it would better be considered as comprising several distinct IBAs. Current threats to the South Georgia avifauna include rats, regional climate change, and incidental mortality in longline and trawl fisheries outside the Southern Ocean. The 2010/11 austral summer marked the start of a major campaign to eliminate rats. Local fisheries are now well regulated but South Georgia albatrosses and petrels are still killed in large numbers in more distant fisheries. Furthermore, there is probably little that can be done to mitigate the effects of climate change.

Numerous studies of wild animal species have documented that population level responses to environmental change are underpinned by individual level phenotypic plasticity. However, where the relationship between an individual trait and a climate variable occurs when both show a trend over time, phenotypic plasticity may be confounded by ageing. We investigated between and within individual change in laying date in the wandering albatross Diomedea exulans, a long‐lived species experiencing a dramatic decline in population size. Laying date has advanced over the last three decades. A mean‐centering analysis demonstrated that this pattern was driven by within‐individual changes as opposed to appearance or disappearance of phenotypes. Furthermore, a lack of between individual effect suggested the change resulted from ageing as opposed to phenotypic plasticity. Females varied significantly in rate of advance, such that those with low past reproductive rates exhibited a negative temporal trend in laying date, whereas birds with moderate to high past reproductive performance showed little change. The population trend was therefore driven by a subset with low past breeding success. An analysis of effects of timing of breeding on breeding success revealed stabilizing selection for relative laying date. Furthermore, current breeding success was positively related to past success rate, which suggests that there may be indirect selection against plasticity in this population. Our results show that population trends can arise from individual level change unrelated to prevailing environmental conditions, thus demonstrating the importance of longitudinal analyses in the interpretation of climate change effects.

SummaryWe review the conservation status of, and threats to, all 346 species of seabirds, based on BirdLife International’s data and assessments for the 2010 IUCN Red List. We show that overall, seabirds are more threatened than other comparable groups of birds and that their status has deteriorated faster over recent decades. The principal current threats at sea are posed by commercial fisheries (through competition and mortality on fishing gear) and pollution, whereas on land, alien invasive predators, habitat degradation and human disturbance are the main threats. Direct exploitation remains a problem for some species both at sea and ashore. The priority actions needed involve: a) formal and effective site protection, especially for Important Bird Area (IBA) breeding sites and for marine IBA feeding and aggregation sites, as part of national, regional and global networks of Marine Protected Areas; b) removal of invasive, especially predatory, alien species (a list of priority sites is provided), as part of habitat and species recovery initiatives; and c) reduction of bycatch to negligible levels, as part of comprehensive implementation of ecosystem approaches to fisheries. The main knowledge gaps and research priorities relate to the three topics above but new work is needed on impacts of aquaculture, energy generation operations and climate change (especially effects on the distribution of prey species and rise in sea level). We summarise the relevant national and international jurisdictional responsibilities, especially in relation to endemic and globally threatened species.

海洋資源を持続的に利用するためには，生態系を考慮したマネジメントが必須である．そのためには，生態系を構成する各要素について膨大な情報を収集し統合しなければならない．しかし，それはかなり困難であるので，効果的な生態系変化のインジケーターを使うことが重要である．海鳥は気候変化にともなう海洋生態系変動，および海洋環境汚染の便利なインジケーターであると信じられている．本論文では，1) 気候変化による海洋生態系変動に対する海鳥の反応，2) 海岸に漂着した海鳥の海洋油汚染インジケーターとしての有効性と海洋汚染の海鳥に対する潜在的インパクト，3) アホウドリ類の現状と保全，特に延縄による混獲についてレビューする．さらに，4) 世界における海鳥モニタリング活動と我が国における海鳥モニタリングの現状について紹介する．最後に，海鳥保全ネットワークの形成に関する提案をする．

Many pelagic seabirds are thought to regulate reproductive effort by adopting a dual foraging strategy, alternating or mixing short foraging trips over local shelf waters (maximising provi- sioning rates) with longer trips over distant oceanic water (allowing restoration of lost condition). Many species also respond to chick condition, decreasing food supply to over-fed, and sometimes increasing it to under-fed chicks. Analysis of tracking data from 4 albatross species breeding at South Georgia provided evidence that adults responded to prevailing environmental conditions, but did not provide evidence for a dual foraging strategy. Trip durations and maximum foraging ranges tended to follow a positively skewed, unimodal distribution, with the exception of the light-mantled albatross for which no significant modes were apparent. Individual distributions deviated from this, but none were strongly bimodal or showed regular alternation of trip lengths, trip distance or predominant bathy- metric regime. There were significant relationships between meal mass and trip duration, time since the last feed and chick condition on return, reflecting responses to current rather than predicted chick needs. On average, adults returned with smaller meals after 1 to 2 d trips, but otherwise stayed away until a threshold payload was obtained; consequently, provisioning rate (g d -1 ) was much greater after shorter trips. Lack of dual foraging may reflect the diversity of foraging zones available in this highly productive region. By inference, this would mean that adoption of dual foraging elsewhere is a con- sequence of greater heterogeneity in resource availability in waters surrounding those colonies.

Migratory marine vertebrates move annually across remote oceanic water masses crossing international borders. Many anthropogenic threats such as overfishing, bycatch, pollution or global warming put millions of marine migrants at risk especially during their long-distance movements. Therefore, precise knowledge about these migratory movements to understand where and when these animals are more exposed to human impacts is vital for addressing marine conservation issues. Because electronic tracking devices suffer from several constraints, mainly logistical and financial, there is emerging interest in finding appropriate intrinsic markers, such as the chemical composition of inert tissues, to study long-distance migrations and identify wintering sites. Here, using tracked pelagic seabirds and some of their own feathers which were known to be grown at different places and times within the annual cycle, we proved the value of biogeochemical analyses of inert tissue as tracers of marine movements and habitat use. Analyses of feathers grown in summer showed that both stable isotope signatures and element concentrations can signal the origin of breeding birds feeding in distinct water masses. However, only stable isotopes signalled water masses used during winter because elements mainly accumulated during the long breeding period are incorporated into feathers grown in both summer and winter. Our findings shed new light on the simple and effective assignment of marine organisms to distinct oceanic areas, providing new opportunities to study unknown migration patterns of secretive species, including in relation to human-induced mortality on specific populations in the marine environment.

We describe the process used in the fisheries management system of the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR) to minimise seabird bycatch, and the risk-assessment methodology developed to assist this. We examine the progress of several Regional Fishery Management Organisations in taking steps to address seabird bycatch. CCAMLR has the most advanced system of management among the RFMOS covered in this review, and has made the most demonstrable progress in reducing seabird bycatch levels in its longline fisheries. A combination of proven mitigation measures, extensive monitoring by independent observers, annual expert review of seabird bycatch rates and evolving fishery and mitigation practices have been instrumental in reducing seabird bycatch in CCAMLR fisheries.

Conservationists are continually seeking new strategies to reverse population declines and safeguard against species extinctions. Here we evaluate the potential efficacy of a recently proposed approach to offset a major anthropogenic threat to many marine vertebrates: incidental bycatch in commercial fisheries operations. This new approach, compensatory mitigation for marine bycatch (CMMB), is conceived as a way to replace or reduce mandated restrictions on fishing activities with compensatory activities (e. g., removal of introduced predators from islands) funded by levies placed on fishers. While efforts are underway to bring CMMB into policy discussions, to date there has not been a detailed evaluation of CMMB's potential as a conservation tool, and in particular, a list of necessary and sufficient criteria that CMMB must meet to be an effective conservation strategy. Here we present a list of criteria to assess CMMB that are tied to critical ecological aspects of the species targeted for conservation, the range of possible mitigation activities, and the multi-species impact of fisheries bycatch. We conclude that, overall, CMMB has little potential for benefit and a substantial potential for harm if implemented to solve most fisheries bycatch problems. In particular, CMMB is likely to be effective only when applied to short-lived and highly-fecund species (not the characteristics of most bycatch-impacted species) and to fisheries that take few non-target species, and especially few non-seabird species (not the characteristics of most fisheries). Thus, CMMB appears to have limited application and should only be implemented after rigorous appraisal on a case-specific basis; otherwise it has the potential to accelerate declines of marine species currently threatened by fisheries bycatch.