BackgroundResolving threats to widely distributed marine megafauna requires definition of the geographic distributions of both the threats as well as the population unit(s) of interest. In turn, because individual threats can operate on varying spatial scales, their impacts can affect different segments of a population of the same species. Therefore, integration of multiple tools and techniques — including site-based monitoring, genetic analyses, mark-recapture studies and telemetry — can facilitate robust definitions of population segments at multiple biological and spatial scales to address different management and research challenges.Methodology/Principal FindingsTo address these issues for marine turtles, we collated all available studies on marine turtle biogeography, including nesting sites, population abundances and trends, population genetics, and satellite telemetry. We georeferenced this information to generate separate layers for nesting sites, genetic stocks, and core distributions of population segments of all marine turtle species. We then spatially integrated this information from fine- to coarse-spatial scales to develop nested envelope models, or Regional Management Units (RMUs), for marine turtles globally.Conclusions/SignificanceThe RMU framework is a solution to the challenge of how to organize marine turtles into units of protection above the level of nesting populations, but below the level of species, within regional entities that might be on independent evolutionary trajectories. Among many potential applications, RMUs provide a framework for identifying data gaps, assessing high diversity areas for multiple species and genetic stocks, and evaluating conservation status of marine turtles. Furthermore, RMUs allow for identification of geographic barriers to gene flow, and can provide valuable guidance to marine spatial planning initiatives that integrate spatial distributions of protected species and human activities. In addition, the RMU framework — including maps and supporting metadata — will be an iterative, user-driven tool made publicly available in an online application for comments, improvements, download and analysis.

Where conservation resources are limited and conservation targets are diverse, robust yet flexible priority-setting frameworks are vital. Priority-setting is especially important for geographically widespread species with distinct populations subject to multiple threats that operate on different spatial and temporal scales. Marine turtles are widely distributed and exhibit intra-specific variations in population sizes and trends, as well as reproduction and morphology. However, current global extinction risk assessment frameworks do not assess conservation status of spatially and biologically distinct marine turtle Regional Management Units (RMUs), and thus do not capture variations in population trends, impacts of threats, or necessary conservation actions across individual populations. To address this issue, we developed a new assessment framework that allowed us to evaluate, compare and organize marine turtle RMUs according to status and threats criteria. Because conservation priorities can vary widely (i.e. from avoiding imminent extinction to maintaining long-term monitoring efforts) we developed a “conservation priorities portfolio” system using categories of paired risk and threats scores for all RMUs (n = 58). We performed these assessments and rankings globally, by species, by ocean basin, and by recognized geopolitical bodies to identify patterns in risk, threats, and data gaps at different scales. This process resulted in characterization of risk and threats to all marine turtle RMUs, including identification of the world's 11 most endangered marine turtle RMUs based on highest risk and threats scores. This system also highlighted important gaps in available information that is crucial for accurate conservation assessments. Overall, this priority-setting framework can provide guidance for research and conservation priorities at multiple relevant scales, and should serve as a model for conservation status assessments and priority-setting for widespread, long-lived taxa.

17The Chukchi and Beaufort seas are undergoing rapid climate change and increased human 18 activity. Conservation efforts for upper trophic level predators such as seabirds and marine 19 mammals require information on species' distributions and identification of important marine 20 areas. Here we describe broad-scale distributions of seabirds and marine mammals. We 21 examined spatial patterns of relative abundance of seabirds and marine mammals in the eastern 22 Chukchi and western Beaufort seas during summer (. We summarized 49 206 km of shipboard surveys for seabirds 24 and 183 157 km of aerial surveys for marine mammals into a grid of 40-km X 40-km cells. We 25 used Getis-Ord Gi* hotspot analysis to test for cells with higher relative abundance than 26 expected when compared to all cells within the study area. We identified cells representing 27 Kuletz et al_Seabird and Marine Mammal Hotspots in Pacific Arctic_2.27.15 2 single-species and taxonomic group hotspots, cells representing hotspots for multiple species, 28 and cells representing hotspots for both seabirds and marine mammals. The locations of hotspots 29 varied among species but often were located near underwater canyons or over continental shelf 30 features and slopes. Hotspots for seabirds, walrus, and gray whales occurred primarily in the 31 Chukchi Sea. Hotspots for bowhead whales and other pinnipeds (i.e., seals) occurred near 32 Barrow Canyon and along the Beaufort Sea shelf and slope. Hotspots for belugas occurred in 33 both the Chukchi and Beaufort seas. There were three hotspots shared by both seabirds and 34 marine mammals in summer: off Wainwright in the eastern Chukchi Sea, south of Hanna Shoal, 35 and at the mouth of Barrow Canyon. In fall, the only identified shared hotspot occurred at the 36 mouth of Barrow Canyon. Shared hotspots are characterized by strong fronts caused by 37 upwelling and currents, and these areas can have high densities of euphausiids in summer and 38 fall. Due to the high relative abundance of animals and diversity of taxa, these sites are clearly 39 important areas of congregation for seabirds and marine mammals that should be prioritized in 40 the development of management and conservation plans.41 42