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Homer, AK, United States

Hunt G.L.,University of Washington | Renner M.,Tern Again Consulting | Kuletz K.,U.S. Fish and Wildlife Service
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2014

We tested the hypothesis that the distribution of seabird species' associations across the southeastern Bering Sea shelf reflects the underlying ecology of four bathymetrically-defined hydrographic domains: the Inner or Coastal Shelf Domain (depth (Z)<50. m), the Middle Shelf Domain (50. m<. Z<100. m), the Outer Shelf Domain (100. m<. Z<200. m), and the Shelf-Slope Domain (200. m<. Z<3000. m). The domains differ in stratification, which intensifies from winter to summer and breaks down in the fall. To examine seabird distributions with respect to these domains in multiple seasons, we quantified the cross-shelf distribution of species with respect to water depth using a 37-year database. We then used a multivariate tree analysis to group species with similar depth-use distributions, and mapped these clusters against the hydrographic domains. There were three patterns of seabird depth use: an inshore, shallow-water group in summer and fall, but not winter and spring, which conformed roughly to the Inner Shelf Domain; a group of species that were distributed widely across the Middle and Outer Shelf Domains, and a third group of species that occupied the outer portion of the Outer Shelf Domain and the Shelf-Slope Domain. The multivariate tree analysis revealed close correspondence between the seabird-derived domains and the bathymetrically-defined Outer Shelf and Shelf-Slope domains in spring and to a lesser extent in summer. In summer and fall, and to a lesser extent in spring, the seabird groupings showed a differentiation between the Inner Shelf Domain and the Middle Shelf Domain. Seabird-derived differentiation between the Shelf-Slope Domain and the Outer Shelf Domain was strongest in spring and summer. These seasonal patterns likely reflected the seasonal variation in the hydrographic differentiation of the bathymetrically-defined domains. Cross-validation of the multivariate tree analysis showed that the portion of seabird distribution patterns explained by the tree analysis was smallest in winter (when there is no stratification on the middle and inner shelves) and greatest in summer (when stratified water columns result in hydrographically defined domains), as would be expected under our hypothesis. We also examined hypotheses predicting why pursuit diving seabirds most often forage in shallow water whereas surface-foraging (surface-seizing) seabirds are more common over deep offshore waters. The hypothesis for regionally enhanced primary production as a driving factor was not supported for the inshore foraging seabirds but was supported for those foraging over shelf-slope waters. © 2013 Elsevier Ltd.

Renner M.,Tern Again Consulting | Kuletz K.J.,U.S. Fish and Wildlife Service
Marine Pollution Bulletin | Year: 2015

Some of the largest seabird concentrations in the northern hemisphere are intersected by major shipping routes in the Aleutian Archipelago. Risk is the product of the probability and the severity incidents in an area. We build a seasonally explicit model of seabird distribution and combine the densities of seabirds with an oil vulnerability index. We use shipping density, as a proxy for the probability of oil spills from shipping accident (or the intensity chronic oil pollution). We find high-risk (above-average seabird and vessel density) areas around Unimak Pass, south of the Alaska Peninsula, near Buldir Island, and north of Attu Island. Risk to seabirds is greater during summer than during winter, but the month of peak risk (May/July) varies depending on how data is analyzed. The area around Unimak Pass stands out for being at high-risk year-round, whereas passes in the western Aleutians are at high risk mostly during summer. © 2015 Elsevier Ltd.

Renner H.M.,Alaska Maritime National Wildlife Refuge | Romano M.D.,Alaska Maritime National Wildlife Refuge | Renner M.,Tern Again Consulting | Pyare S.,University of Alaska Southeast | And 2 more authors.
Marine Ornithology | Year: 2015

We compiled survey data on 202 Aleutian Tern colonies throughout Alaska and Russia to assess the current status and colony sizes and to evaluate whether there had been changes in recent decades. We fit a Poisson generalized linear mixed model to all available counts of Alaskan colonies since 1960, excluding colonies in which the temporal spread of counts was < 6 years. Russian data were not included in the trend model due to our inability to resolve dates on a number of counts. We estimate that numbers at known colonies in Alaska have declined 8.1% annually since 1960 or 92.9% over three generations (33 years; 95% CI = 83.3%–97%), with large colonies experiencing greater declines than small colonies. Trends at known colonies within discrete geographic regions of Alaska (Aleutian Islands, Bering Sea, Chukchi Sea, Gulf of Alaska and Kodiak Island) were consistently negative. The most recent counts of all known Alaskan colonies summed to 5 529 birds. This estimate should be considered a rough minimum because it does not account for colonies that have not been surveyed in recent years — the size of which may have changed — or for the fact that the surveys conducted were neither systematic nor inclusive of all potential habitats. In Russia, the sum of the most recent count of all colonies was 25 602 individuals, indicating that Russia may host approximately 80% of the world population. Numbers in some regions in Russia appear to have increased substantially in recent decades, especially on Sakhalin Island and the southern coast of the Koryak Highland. We have no data to identify any population-level stressor that could explain the apparent reduction in numbers in Alaska. However, predation, egging and other anthropogenic disturbances, and degraded habitat may cause population change at local levels. If this overall pattern cannot be explained by other possible but unlikely factors (e.g. establishment of large colonies in new locations within Alaska, or major shifts between Alaska and Russia), then the observed trends in Alaska are, indeed, alarming. Therefore, we urge close monitoring of known colonies within Alaska, studies of dispersal, establishment of management practices to insulate colonies from human disturbance, and more concerted efforts among Alaskan and Russian partners. © 2015, Marine Ornithology. All rights reserved.

Suryan R.M.,Oregon State University | Kuletz K.J.,U.S. Fish and Wildlife Service | Parker-Stetter S.L.,University of Washington | Parker-Stetter S.L.,National Oceanic and Atmospheric Administration | And 5 more authors.
Marine Ecology Progress Series | Year: 2016

The Bering Sea is a highly productive ecosystem with abundant prey populations in the summer that support some of the largest seabird colonies in the Northern Hemisphere. In the fall, the Bering Sea is used by large numbers of migrants and post-breeding seabirds. We used over 22 000 km of vessel-based surveys carried out during summer (June to July) and fall (late August to October) from 2008 to 2010 over the southeast Bering Sea to examine annual and seasonal changes in seabird communities and spatial relationships with concurrently sampled prey. Deep-diving murres Uria spp., shallow-diving shearwaters Ardenna spp., and surface-foraging northern fulmars Fulmarus glacialis and kittiwakes Rissa spp. dominated summer and fall seabird communities. Seabird densities in summer were generally less than half of fall densities and species richness was lower in summer than in fall. Summer seabird densities had high interannual variation (highest in 2009), whereas fall densities varied little among years. Seabirds were more spatially clustered around breeding colonies and the outer continental shelf in the summer and then dispersed throughout the middle and inner shelf in fall. In summer, the abundance of age-1 walleye pollock Gadus chal co-grammus along with spatial (latitude and longitude) and temporal (year) variables best explained broad-scale seabird distribution. In contrast, seabirds in fall had weaker associations with spatial and temporal variables and stronger associations with different prey species or groups. Our results demonstrate seasonal shifts in the distribution and foraging patterns of seabirds in the southeastern Bering Sea with a greater dependence on prey occurring over the middle and inner shelf in fall. © 2016 SAMS.

Renner M.,Tern Again Consulting | Huntington H.P.,Tern Again Consulting
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2014

Alaska Native subsistence hunters and fishers are engaged in environmental sampling, influenced by harvest technology and cultural preferences as well as biogeographical factors. We compared subsistence harvest patterns in 35 communities along the Bering, Chukchi, and Beaufort coasts of Alaska to identify affinities and groupings, and to compare those results with previous ecological analyses done for the same region. We used hierarchical cluster analysis to reveal spatial patterns in subsistence harvest records of coastal Alaska Native villages from the southern Bering Sea to the Beaufort Sea. Three main clusters were identified, correlating strongly with geography. The main division separates coastal villages of western Alaska from arctic villages along the northern Chukchi and Beaufort Seas and on islands of the Bering Sea. K-means groupings corroborate this result, with some differences. The second node splits the arctic villages, along the Chukchi, Beaufort and northern Bering Seas, where marine mammals dominate the harvest, from those on islands of the Bering Sea, characterized by seabird and seal harvests. These patterns closely resemble eco-regions proposed on biological grounds. Biogeography thus appears to be a significant factor in groupings by harvest characteristics, suggesting that subsistence harvests are a viable form of ecosystem sampling. © 2014 Elsevier Ltd.

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