Browsing by Author "Stanworth, Andrew"
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- A framework for mapping the distribution of seabirds by integrating tracking, demography and phenologyPublication . Carneiro, Ana Paula B.; Pearmain, Elizabeth J.; Oppel, Steffen; Clay, Thomas A.; Phillips, Richard A.; Bonnet‐Lebrun, Anne‐Sophie; Wanless, Ross M.; Abraham, Edward; Richard, Yvan; Rice, Joel; Handley, Jonathan; Davies, Tammy E.; Dilley, Ben J.; Ryan, Peter G.; Small, Cleo; Arata, Javier; Arnould, John P. Y.; Bell, Elizabeth; Bugoni, Leandro; Letizia, Campioni; Catry, Paulo; Cleeland, Jaimie; Deppe, Lorna; Elliott, Graeme; Freeman, Amanda; Gonzalez-Solis, Jacob; Granadeiro, José Pedro; Grémillet, David; Landers, Todd J.; Makhado, Azwianewi; Nel, Deon; Nicholls, David G.; Rexer‐Huber, Kalinka; Robertson, Christopher J. R.; Sagar, Paul M.; Scofield, Paul; Stahl, Jean‐Claude; Stanworth, Andrew; Stevens, Kim L.; Trathan, Philip N.; Thompson, David R.; Torres, Leigh; Walker, Kath; Waugh, Susan M.; Weimerskirch, Henri; Dias, Maria P.1. 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. 2. Here we develop a methodological framework for estimating populationlevel 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. 3. 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 lifehistory stages. 4. 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.
- Local-scale impacts of extreme events drive demographic asynchrony in neighbouring top predator populationsPublication . Ventura, Francesco; Stanworth, Andrew; Crofts, Sarah; Kuepfer, Amanda; Catry, PauloExtreme weather events are among the most critical aspects of climate change, but our understanding of their impacts on biological populations remains limited. Here, we exploit the rare opportunity provided by the availability of concurrent longitudinal demographic data on two neighbouring marine top predator populations (the black-browed albatross, Thalassarche melanophris, breeding in two nearby colonies) hit by an exceptionally violent storm during one study year. The aim of this study is to quantify the demographic impacts of extreme events on albatrosses and test the hypothesis that extreme events would synchronously decrease survival rates of neighbouring populations. Using demographic modelling we found that, contrary to our expectation, the storm affected the survival of albatrosses from only one of the two colonies, more than doubling the annual mortality rate compared to the study average. Furthermore, the effects of storms on adult survival would lead to substantial population declines (up to 2% per year) under simulated scenarios of increased storm frequencies. We, therefore, conclude that extreme events can result in very different local-scale impacts on sympatric populations. Crucially, by driving demographic asynchrony, extreme events can hamper our understanding of the demographic responses of wild populations to mean, long-term shifts in climate.
- Metapopulation distribution shapes year‐round overlap with fisheries for a circumpolar seabirdPublication . Rexer‐Huber, Kalinka; Clay, Thomas A.; Catry, Paulo; Debski, Igor; Parker, Graham; Ramos, Raül; Robertson, Bruce C.; Ryan, Peter G.; Sagar, Paul M.; Stanworth, Andrew; Thompson, David R.; Tuck, Geoffrey N.; Weimerskirch, Henri; Phillips, Richard A.Although fisheries bycatch is the greatest threat to many migratory marine megafauna, it remains unclear how population exposure to bycatch varies across the global range of threatened species. Such assessments across multiple populations are crucial for understanding variation in impacts and for identifying the management bodies responsible for reducing bycatch. Here, we combine extensive biologging data from white‐chinned petrel (Procellaria aequinoctialis) populations (representing >98% of their global breeding population) with pelagic and demersal longline and trawl fishing effort to map the global distribution and fisheries‐overlap hotspots for the most bycaught seabird in the Southern Hemisphere. We tracked the year‐round movements of 132 adults in 2006–2018 and examined spatial overlap among seven populations comprising three genetically distinct groupings (metapopulations). Foraging areas during the nonbreeding season were more concentrated than during breeding, with birds from all populations migrating to continental shelf or upwelling zones, but with low spatial overlap among metapopulations. Fisheries overlap differed more among than within metapopulations, underlining that these should be considered separate management units. Overlap with pelagic longline fisheries was greatest for Indian Ocean populations, and from the fleets of South Africa, Japan, Taiwan, and Spain, off southern Africa and in the High Seas. Overlap with demersal longline and trawl fisheries was greatest for Indian and Atlantic Ocean populations, within the Exclusive Economic Zones of South Africa, Namibia, and Argentina, and with the South Korean demersal longline fleet in the High Seas. The high overlap with South Korean longliners in the southwest Atlantic Ocean is of particular concern as demersal fishing in this region is not covered by any Regional Fisheries Management Organization (RFMO). We also identified fisheries‐overlap hotspots within RFMOs where there are no seabird‐bycatch mitigation requirements (1.5%–53.1% of total overlap within the area of competence of each RFMO), or where current mitigation regulations need to be strengthened. Our recommendations are that management bodies target the high‐priority fisheries we have identified for improved bycatch monitoring, mandatory best‐practice bycatch mitigation, and close monitoring of compliance, given the conservation concerns for white‐chinned petrels and other threatened seabirds. Biologging, Bycatch mitigatio, Geolocator, Longline fisheries, Migratory connectivity, Regional Fisheries Management Organization, Trawl fisheries, White-chinned petrel
- Progressing delineations of key biodiversity areas for seabirds, and their application to management of coastal seasPublication . Handley, Jonathan; Harte, Emma; Stanworth, Andrew; Poncet, Sally; Catry, Paulo; Cleminson, Sacha; Crofts, Sarah; Dias, MariaAim: Decision-making products that support effective marine spatial planning are essential for guiding efforts that enable conservation of biodiversity facing increasing pressures. Key Biodiversity Areas (KBAs) are a product recently agreed upon by an international network of organizations for identifying globally important areas. Utilizing the KBA framework, and by developing a conservative protocol to identify sites, we identify globally importants places for breeding seabirds throughout the coastal seas of a national territory. We inform marine spatial planning by evaluating potential activities that may impact species and how a proposed network of Marine Management Areas (MMAs) overlap with important sites. Location: Southwest Atlantic Ocean. Methods: We collated a national inventory of all breeding locations for seabirds, including abundance records where available, and complementary estimates of at-sea distribution. We delineated areas of importance in coastal seas following approaches tailored to the ecology of species and assessed areas against global KBA criteria. To determine opportunities for species conservation and management, we reviewed which human activities have been documented to impact the target species globally via IUCN Red List accounts, and also assessed the overlap of important sites with a proposed MMA network. Results: We identified global KBAs for nine seabird species (Anatidae, Diomedeidae, Laridae, Procellariidae, Spheniscidae, Stercorariidae) throughout national coastal seas. Globally important areas where multiple species overlapped were only partially accounted for in key zones of the proposed MMA network. Main Conclusions: Development of a conservative protocol to identify marine sites for assessment against KBA criteria, revealed opportunities for enhancing a network of proposed Marine Management Areas in coastal seas. The framework we apply in this study has broad relevance for other systems where the design or review of management plans for the marine environment is required.