37We present the first objective quantitative assessment of the threats to all 359 species of seabirds, 38 identify the main challenges facing them, and outline priority actions for their conservation. We applied 39 the standardised Threats Classification Scheme developed for the IUCN Red List to objectively assess 40 threats to each species and analysed the data according to global IUCN threat status, taxonomic group, 41and primary foraging habitat (coastal or pelagic). The top three threats to seabirds in terms of number 42 of species affected and average impact are: invasive alien species, affecting 165 species across all the 43 most threatened groups; bycatch in fisheries, affecting fewer species (100) but with the greatest 44 average impact; and climate change/severe weather, affecting 96 species. In addition to impacting 86% 45 of globally threatened species, these three top threats also affect 81% of the species currently classified 46as Near Threatened or as Least Concern but declining. Reversing these three threats would benefit two-47 thirds of all species and c. 380 million individual seabirds (c. 45% of the total global seabird population). 48Most seabirds (c. 70%), especially globally threatened species, face multiple threats. For albatrosses, 49 petrels and penguins in particular (the three most threatened groups of seabirds), it is essential to 50 tackle both terrestrial and marine threats to reverse declines. As the negative effects of climate change 51 are harder to mitigate, it is vital to compensate by addressing other major threats that often affect the 52 same species, such as invasive alien species and bycatch, for which proven solutions exist. 53 54

Aim -Enhanced management of areas important for marine biodiversity are now obligations under a range of international treaties. Tracking data provide unparalleled information on the distribution of marine taxa, but there are no agreed guidelines that ensure these data are used consistently to identify biodiversity hotspots and inform marine management decisions. Here we develop methods to standardise the analysis of tracking data to identify sites of conservation importance at global and regional scales.Location -We applied these methods to the largest available compilation of seabird tracking data, covering 60 species, collected from 55 deployment locations ranging from the poles to the tropics.Methods -Key developments include a test for pseudo-replication to assess the independence of two groups of tracking data, an objective approach to define species-specific smoothing parameters (h values) for kernel density estimation based on area-restricted search behaviour, and an analysis to determine whether sites identified from tracked individuals are also representative for the wider population.

Bycatch in longline fisheries is believed to govern the adverse conservation status of many seabird species, but no comprehensive global assessment has been undertaken. We reviewed the extent of seabird bycatch in all longline fisheries for which data are available. Despite the many inadequacies and assumptions contained therein, we estimated that at least 160 000 (and potentially in excess of 320 000) seabirds are killed annually. Most frequently caught are albatrosses, petrels and shearwaters, with current levels of mortality liable to be unsustainable for some species and populations. Where realistic comparisons can be made, with data from the 1990s, there is evidence of substantially reduced bycatch in some key fisheries. Reductions stem from decreased fishing effort (especially in illegal, unreported and unregulated fishing in the Southern Ocean), and greater and more effective use of technical mitigation measures, notably in demersal fisheries. However, bycatch problems in other fisheries have also emerged. Current concerns include those with previously unidentified bycatch problems (e.g. Spanish Gran Sol demersal fleet) and those where bycatch was identified, but where persistent data gaps prevented adequate assessments of the scale of the impact (e.g. Nordic demersal fisheries). Future assessments will only achieve greater precision when minimum standards of data collection, reporting and analysis are implemented by longline fishing fleets and the relevant regional fishery management organisations. Those fisheries in which bycatch has been substantially reduced demonstrate that the problem of seabird bycatch could be reduced to negligible proportions by enforced implementation of appropriate best-practice mitigation devices and techniques.

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Tuck, G. N., Phillips, R. A., Small, C., Thomson, R. B., Klaer, N. L., Taylor, F., Wanless, R. M., and Arrizabalaga, H. 2011. An assessment of seabird–fishery interactions in the Atlantic Ocean. – ICES Journal of Marine Science, 68: 1628–1637. Currently, 17 of 22 albatross species are listed as Vulnerable, Endangered, or Critically endangered by the International Union for the Conservation of Nature (IUCN). Incidental mortality in fisheries is by far the most widespread cause of the population declines observed for these and other closely related species. In 2006, the International Commission for the Conservation of Atlantic Tunas (ICCAT) requested an assessment of the threat from their fisheries to all seabirds that breed or forage within their jurisdiction. Methods were developed to assess the potential consequences of fishing for more than 60 populations of seabird. The assessment framework involved the identification of at-risk populations, overlap analyses, estimation of total bycatch, and an evaluation of the impact of the bycatch on key selected populations for which there were sufficient data on bird distribution and demography. These were the wandering and black-browed albatrosses of South Georgia and the Atlantic yellow-nosed and Tristan albatrosses of Gough Island. Summary results from the seabird assessment are presented, revealing that ICCAT longline fisheries catch substantial numbers of seabirds, with potentially significant conservation implications. If this mortality is not reduced, the numbers of breeding birds in some populations will continue to decline, threatening their long-term viability.

The identification of geographic areas where the densities of animals are highest across their annual cycles is a crucial step in conservation planning. In marine environments, however, it can be particularly difficult to map the distribution of species, and the methods used are usually biased towards adults, neglecting the distribution of other life‐history stages even though they can represent a substantial proportion of the total population. Here we develop a methodological framework for estimating population‐level density distributions of seabirds, integrating tracking data across the main life‐history stages (adult breeders and non‐breeders, juveniles and immatures). We incorporate demographic information (adult and juvenile/immature survival, breeding frequency and success, age at first breeding) and phenological data (average timing of breeding and migration) to weight distribution maps according to the proportion of the population represented by each life‐history stage. We demonstrate the utility of this framework by applying it to 22 species of albatrosses and petrels that are of conservation concern due to interactions with fisheries. Because juveniles, immatures and non‐breeding adults account for 47%–81% of all individuals of the populations analysed, ignoring the distributions of birds in these stages leads to biased estimates of overlap with threats, and may misdirect management and conservation efforts. Population‐level distribution maps using only adult distributions underestimated exposure to longline fishing effort by 18%–42%, compared with overlap scores based on data from all life‐history stages. Synthesis and applications. Our framework synthesizes and improves on previous approaches to estimate seabird densities at sea, is applicable for data‐poor situations, and provides a standard and repeatable method that can be easily updated as new tracking and demographic data become available. We provide scripts in the R language and a Shiny app to facilitate future applications of our approach. We recommend that where sufficient tracking data are available, this framework be used to assess overlap of seabirds with at‐sea threats such as overharvesting, fisheries bycatch, shipping, offshore industry and pollutants. Based on such an analysis, conservation interventions could be directed towards areas where they have the greatest impact on populations.

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1. 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).2. 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 lifehistory 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.3. Overlap with both pelagic and demersal longline fisheries was highest for blackbrowed albatrosses, then white-chinned petrels, wandering and grey-headed albatrosses, whereas overlap with trawl fisheries was highest for white-chinned petrels.4. 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 | 1883Journal of Applied Ecology CLAY et AL.