Modeling spatiotemporal abundance and movement dynamics using an integrated spatial capture-recapture movement model

Animal movement is a fundamental ecological process affecting the survival and reproduction of individuals, the structure of populations, and the dynamics of communities. Methods to quantify animal movement and spatiotemporal abundances, however, are generally separate and therefore omit linkages between individual-level and population-level processes. We describe an integrated spatial capture-recapture (SCR) movement model to jointly estimate (1) the number and distribution of individuals in a defined spatial region and (2) movement of those individuals through time. We applied our model to a study of polar bears (Ursus maritimus) in a 28,125 km² survey area of the eastern Chukchi Sea, USA in 2015 that incorporated capture-recapture and telemetry data. In simulation studies, the model provided unbiased estimates of movement, abundance, and detection parameters using a bivariate normal random walk and correlated random walk movement process. Our case study provided detailed evidence of directional movement persistence for both male and female bears, where individuals regularly traversed areas larger than the survey area during the 36-day study period. Scaling from individual- to population-level inferences, we found that densities varied from <0.75 bears/625 km² grid cell/day in nearshore cells to 1.6-2.5 bears/grid cell/day for cells surrounded by sea ice. Daily abundance estimates ranged from 53 to 69 bears, with no trend across days. The cumulative number of unique bears that used the survey area increased through time due to movements into and out of the area, resulting in an estimated 171 individuals using the survey area during the study (95% credible interval 124-250). Abundance estimates were similar to a previous multiyear integrated population model using capture-recapture and telemetry data (2008-2016; Regehr et al., Scientific Reports 8:16780, 2018). Overall, the SCR-movement model successfully quantified both individual- and population-level space use, including the effects of landscape characteristics on movement, abundance, and detection, while linking the movement and abundance processes to directly estimate density within a prescribed spatial region and temporal period. Integrated SCR-movement models provide a generalizable approach to incorporate greater movement realism into population dynamics and link movement to emergent properties including spatiotemporal densities and abundances.

Intrapopulation differences in polar bear movement and step selection patterns

BACKGROUND

The spatial ecology of individuals often varies within a population or species. Identifying how individuals in different classes interact with their environment can lead to a better understanding of population responses to human activities and environmental change and improve population estimates. Most inferences about polar bear (Ursus maritimus) spatial ecology are based on data from adult females due to morphological constraints on applying satellite radio collars to other classes of bears. Recent studies, however, have provided limited movement data for adult males and sub-adults of both sexes using ear-mounted and glue-on tags. We evaluated class-specific movements and step selection patterns for polar bears in the Chukchi Sea subpopulation during spring.

METHODS

We developed hierarchical Bayesian models to evaluate polar bear movement (i.e., step length and directional persistence) and step selection at the scale of 4-day step lengths. We assessed differences in movement and step selection parameters among the three classes of polar bears (i.e., adult males, sub-adults, and adult females without cubs-of-the-year).

RESULTS

Adult males had larger step lengths and less directed movements than adult females. Sub-adult movement parameters did not differ from the other classes but point estimates were most similar to adult females. We did not detect differences among polar bear classes in step selection parameters and parameter estimates were consistent with previous studies.

CONCLUSIONS

Our findings support the use of estimated step selection patterns from adult females as a proxy for other classes of polar bears during spring. Conversely, movement analyses indicated that using data from adult females as a proxy for the movements of adult males is likely inappropriate. We recommend that researchers consider whether it is valid to extend inference derived from adult female movements to other classes, based on the questions being asked and the spatial and temporal scope of the data. Because our data were specific to spring, these findings highlight the need to evaluate differences in movement and step selection during other periods of the year, for which data from ear-mounted and glue-on tags are currently lacking.

Demographic risk assessment for a harvested species threatened by climate change: polar bears in the Chukchi Sea

Climate change threatens global biodiversity. Many species vulnerable to climate change are important to humans for nutritional, cultural, and economic reasons. Polar bears Ursus maritimus are threatened by sea-ice loss and represent a subsistence resource for Indigenous people. We applied a novel population modeling-management framework that is based on species life history and accounts for habitat loss to evaluate subsistence harvest for the Chukchi Sea (CS) polar bear subpopulation. Harvest strategies followed a state-dependent approach under which new data were used to update the harvest on a predetermined management interval. We found that a harvest strategy with a starting total harvest rate of 2.7% (˜85 bears/yr at current abundance), a 2:1 male-to-female ratio, and a 10-yr management interval would likely maintain subpopulation abundance above maximum net productivity level for the next 35 yr (approximately three polar bear generations), our primary criterion for sustainability. Plausible bounds on starting total harvest rate were 1.7-3.9%, where the range reflects uncertainty due to sampling variation, environmental variation, model selection, and differing levels of risk tolerance. The risk of undesired demographic outcomes (e.g., overharvest) was positively related to harvest rate, management interval, and projected declines in environmental carrying capacity; and negatively related to precision in population data. Results reflect several lines of evidence that the CS subpopulation has been productive in recent years, although it is uncertain how long this will last as sea-ice loss continues. Our methods provide a template for balancing trade-offs among protection, use, research investment, and other factors. Demographic risk assessment and state-dependent management will become increasingly important for harvested species, like polar bears, that exhibit spatiotemporal variation in their response to climate change.

Seal body condition and atmospheric circulation patterns influence polar bear body condition, recruitment, and feeding ecology in the Chukchi Sea

Polar bears (Ursus maritimus) are experiencing loss of sea ice habitats used to access their marine mammal prey. Simultaneously, ocean warming is changing ecosystems that support marine mammal populations. The interactive effects of sea ice and prey are not well understood yet may explain spatial-temporal variation in the response of polar bears to sea ice loss. Here, we examined the potential combined effects of sea ice, seal body condition, and atmospheric circulation patterns on the body condition, recruitment, diet, and feeding probability of 469 polar bears captured in the Chukchi Sea, 2008-2017. The body condition of ringed seals (Pusa hispida), the primary prey of females and subadults, was related to dietary proportions of ringed seal, feeding probability, and the body condition of females and cubs. In contrast, adult males consumed more bearded seals (Erignathus barbatus) and exhibited better condition when bearded seal body condition was higher. The litter size, number of yearlings per adult female, and the condition of dependent young were higher following winters characterized by low Arctic Oscillation conditions, consistent with a growing number of studies. Body condition, recruitment, and feeding probability were either not associated or negatively associated with sea ice conditions, suggesting that, unlike some subpopulations, Chukchi Sea bears are not currently limited by sea ice availability. However, spring sea ice cover declined 2% per year during our study reaching levels not previously observed in the satellite record and resulting in the loss of polar bear hunting and seal pupping habitat. Our study suggests that the status of ice seal populations is likely an important factor that can either compound or mitigate the response of polar bears to sea ice loss over the short term. In the long term, neither polar bears nor their prey are likely robust to limitless loss of their sea ice habitat.

Aerial survey estimates of polar bears and their tracks in the Chukchi Sea

Polar bears are of international conservation concern due to climate change but are difficult to study because of low densities and an expansive, circumpolar distribution. In a collaborative U.S.-Russian effort in spring of 2016, we used aerial surveys to detect and estimate the abundance of polar bears on sea ice in the Chukchi Sea. Our surveys used a combination of thermal imagery, digital photography, and human observations. Using spatio-temporal statistical models that related bear and track densities to physiographic and biological covariates (e.g., sea ice extent, resource selection functions derived from satellite tags), we predicted abundance and spatial distribution throughout our study area. Estimates of 2016 abundance ([Formula: see text]) ranged from 3,435 (95% CI: 2,300-5,131) to 5,444 (95% CI: 3,636-8,152) depending on the proportion of bears assumed to be missed on the transect line during Russian surveys (g(0)). Our point estimates are larger than, but of similar magnitude to, a recent estimate for the period 2008-2016 ([Formula: see text]; 95% CI 1,522-5,944) derived from an integrated population model applied to a slightly smaller area. Although a number of factors (e.g., equipment issues, differing platforms, low sample sizes, size of the study area relative to sampling effort) required us to make a number of assumptions to generate estimates, it establishes a useful lower bound for abundance, and suggests high spring polar bear densities on sea ice in Russian waters south of Wrangell Island. With future improvements, we suggest that springtime aerial surveys may represent a plausible avenue for studying abundance and distribution of polar bears and their prey over large, remote areas.

Mapping potential effects of proposed roads on migratory connectivity for a highly mobile herbivore using circuit theory

Migration is common worldwide as species access spatiotemporally varying resources and avoid predators and parasites. However, long-distance migrations are increasingly imperiled due to development and habitat fragmentation. Improved understanding of migratory behavior has implications for conservation and management of migratory species, allowing identification and protection of seasonal ranges and migration corridors. We present a technique that applies circuit theory to predict future effects of development by analyzing season-specific resistance to movement from anthropogenic and natural environmental features across an entire migratory path. We demonstrate the utility of our approach by examining potential effects of a proposed road system on barren ground caribou (Rangifer tarandus granti) and subsistence hunters in northern Alaska. Resource selection functions revealed migratory selection by caribou. We tested five scenarios relating habitat selection to landscape resistance using Circuitscape and GPS telemetry data. To examine the effect of potential roads on connectivity of migrating animals and human hunters, we compared current flow values near communities in the presence of proposed roads. Caribou avoided dense vegetation, rugged terrain, major rivers, and existing roads in both spring and fall. A negative linear relationship between resource selection and landscape resistance was strongly supported for fall migration while spring migration featured a negative logarithmic relationship. Overall patterns of caribou connectivity remained similar in the presence of proposed roads, though reduced current flow was predicted for communities near the center of current migration areas. Such data can inform decisions to allow or disallow projects or to select among alternative development proposals and mitigation measures, though consideration of cumulative effects of development is needed. Our approach is flexible and can easily be adapted to other species, locations and development scenarios to expand understanding of movement behavior and to evaluate proposed developments. Such information is vital to inform policy decisions that balance new development, resource user needs, and preservation of ecosystem function.

Identifying reliable indicators of fitness in polar bears

Animal structural body size and condition are often measured to evaluate individual health, identify responses to environmental change and food availability, and relate food availability to effects on reproduction and survival. A variety of condition metrics have been developed but relationships between these metrics and vital rates are rarely validated. Identifying an optimal approach to estimate the body condition of polar bears is needed to improve monitoring of their response to decline in sea ice habitat. Therefore, we examined relationships between several commonly used condition indices (CI), body mass, and size with female reproductive success and cub survival among polar bears (Ursus maritimus) measured in two subpopulations over three decades. To improve measurement and application of morphometrics and CIs, we also examined whether CIs are independent of age and structural size–an important assumption for monitoring temporal trends—and factors affecting measurement precision and accuracy. Maternal CIs and mass measured the fall prior to denning were related to cub production. Similarly, maternal CIs, mass, and length were related to the mass of cubs or yearlings that accompanied her. However, maternal body mass, but not CIs, measured in the spring was related to cub production and only maternal mass and length were related to the probability of cub survival. These results suggest that CIs may not be better indicators of fitness than body mass in part because CIs remove variation associated with body size that is important in affecting fitness. Further, CIs exhibited variable relationships with age for growing bears and were lower for longer bears despite body length being related to cub survival and female reproductive success. These results are consistent with findings from other species indicating that body mass is a useful metric to link environmental conditions and population dynamics.

Accounting for phenology in the analysis of animal movement

The analysis of animal tracking data provides important scientific understanding and discovery in ecology. Observations of animal trajectories using telemetry devices provide researchers with information about the way animals interact with their environment and each other. For many species, specific geographical features in the landscape can have a strong effect on behavior. Such features may correspond to a single point (eg, dens or kill sites), or to higher dimensional subspaces (eg, rivers or lakes). Features may be relatively static in time (eg, coastlines or home-range centers), or may be dynamic (eg, sea ice extent or areas of high-quality forage for herbivores). We introduce a novel model for animal movement that incorporates active selection for dynamic features in a landscape. Our approach is motivated by the study of polar bear (Ursus maritimus) movement. During the sea ice melt season, polar bears spend much of their time on sea ice above shallow, biologically productive water where they hunt seals. The changing distribution and characteristics of sea ice throughout the year mean that the location of valuable habitat is constantly shifting. We develop a model for the movement of polar bears that accounts for the effect of this important landscape feature. We introduce a two-stage procedure for approximate Bayesian inference that allows us to analyze over 300 000 observed locations of 186 polar bears from 2012 to 2016. We use our model to estimate a spatial boundary of interest to wildlife managers that separates two subpopulations of polar bears from the Beaufort and Chukchi seas.

Integrated Population Modeling Provides the First Empirical Estimates of Vital Rates and Abundance for Polar Bears in the Chukchi Sea

Large carnivores are imperiled globally, and characteristics making them vulnerable to extinction (e.g., low densities and expansive ranges) also make it difficult to estimate demographic parameters needed for management. Here we develop an integrated population model to analyze capture-recapture, radiotelemetry, and count data for the Chukchi Sea subpopulation of polar bears (Ursus maritimus), 2008-2016. Our model addressed several challenges in capture-recapture studies for polar bears by including a multievent structure reflecting location and life history states, while accommodating state uncertainty. Female breeding probability was 0.83 (95% credible interval [CRI] = 0.71-0.90), with litter sizes of 2.18 (95% CRI = 1.71-2.82) for age-zero and 1.61 (95% CRI = 1.46-1.80) for age-one cubs. Total adult survival was 0.90 (95% CRI = 0.86-0.92) for females and 0.89 (95% CRI = 0.83-0.93) for males. Spring on-ice densities west of Alaska were 0.0030 bears/km2 (95% CRI = 0.0016-0.0060), similar to 1980s-era density estimates although methodological differences complicate comparison. Abundance of the Chukchi Sea subpopulation, derived by extrapolating density from the study area using a spatially-explicit habitat metric, was 2,937 bears (95% CRI = 1,552-5,944). Our findings are consistent with other lines of evidence suggesting the Chukchi Sea subpopulation has been productive in recent years, although it is uncertain how long this will continue given sea-ice loss due to climate change.

Potential impacts of offshore oil spills on polar bears in the Chukchi Sea

Sea ice decline is anticipated to increase human access to the Arctic Ocean allowing for offshore oil and gas development in once inaccessible areas. Given the potential negative consequences of an oil spill on marine wildlife populations in the Arctic, it is important to understand the magnitude of impact a large spill could have on wildlife to inform response planning efforts. In this study we simulated oil spills that released 25,000 barrels of oil for 30 days in autumn originating from two sites in the Chukchi Sea (one in Russia and one in the U.S.) and tracked the distribution of oil for 76 days. We then determined the potential impact such a spill might have on polar bears (Ursus maritimus) and their habitat by overlapping spills with maps of polar bear habitat and movement trajectories. Only a small proportion (1-10%) of high-value polar bear sea ice habitat was directly affected by oil sufficient to impact bears. However, 27-38% of polar bears in the region were potentially exposed to oil. Oil consistently had the highest probability of reaching Wrangel and Herald islands, important areas of denning and summer terrestrial habitat. Oil did not reach polar bears until approximately 3 weeks after the spills. Our study found the potential for significant impacts to polar bears under a worst case discharge scenario, but suggests that there is a window of time where effective containment efforts could minimize exposure to bears. Our study provides a framework for wildlife managers and planners to assess the level of response that would be required to treat exposed wildlife and where spill response equipment might be best stationed. While the size of spill we simulated has a low probability of occurring, it provides an upper limit for planners to consider when crafting response plans.

Spring fasting behavior in a marine apex predator provides an index of ecosystem productivity

The effects of declining Arctic sea ice on local ecosystem productivity are not well understood but have been shown to vary inter-specifically, spatially, and temporally. Because marine mammals occupy upper trophic levels in Arctic food webs, they may be useful indicators for understanding variation in ecosystem productivity. Polar bears (Ursus maritimus) are apex predators that primarily consume benthic and pelagic-feeding ice-associated seals. As such, their productivity integrates sea ice conditions and the ecosystem supporting them. Declining sea ice availability has been linked to negative population effects for polar bears but does not fully explain observed population changes. We examined relationships between spring foraging success of polar bears and sea ice conditions, prey productivity, and general patterns of ecosystem productivity in the Beaufort and Chukchi Seas (CSs). Fasting status (≥7 days) was estimated using serum urea and creatinine levels of 1,448 samples collected from 1,177 adult and subadult bears across three subpopulations. Fasting increased in the Beaufort Sea between 1983-1999 and 2000-2016 and was related to an index of ringed seal body condition. This change was concurrent with declines in body condition of polar bears and observed changes in the diet, condition and/or reproduction of four other vertebrate consumers within the food chain. In contrast, fasting declined in CS polar bears between periods and was less common than in the two Beaufort Sea subpopulations consistent with studies demonstrating higher primary productivity and maintenance or improved body condition in polar bears, ringed seals, and bearded seals despite recent sea ice loss in this region. Consistency between regional and temporal variation in spring polar bear fasting and food web productivity suggests that polar bears may be a useful indicator species. Furthermore, our results suggest that spatial and temporal ecological variation is important in affecting upper trophic-level productivity in these marine ecosystems.

Invariant polar bear habitat selection during a period of sea ice loss

Climate change is expected to alter many species' habitat. A species' ability to adjust to these changes is partially determined by their ability to adjust habitat selection preferences to new environmental conditions. Sea ice loss has forced polar bears (Ursus maritimus) to spend longer periods annually over less productive waters, which may be a primary driver of population declines. A negative population response to greater time spent over less productive water implies, however, that prey are not also shifting their space use in response to sea ice loss. We show that polar bear habitat selection in the Chukchi Sea has not changed between periods before and after significant sea ice loss, leading to a 75% reduction of highly selected habitat in summer. Summer was the only period with loss of highly selected habitat, supporting the contention that summer will be a critical period for polar bears as sea ice loss continues. Our results indicate that bears are either unable to shift selection patterns to reflect new prey use patterns or that there has not been a shift towards polar basin waters becoming more productive for prey. Continued sea ice loss is likely to further reduce habitat with population-level consequences for polar bears.

Increased Arctic sea ice drift alters adult female polar bear movements and energetics

Recent reductions in thickness and extent have increased drift rates of Arctic sea ice. Increased ice drift could significantly affect the movements and the energy balance of polar bears (Ursus maritimus) which forage, nearly exclusively, on this substrate. We used radio-tracking and ice drift data to quantify the influence of increased drift on bear movements, and we modeled the consequences for energy demands of adult females in the Beaufort and Chukchi seas during two periods with different sea ice characteristics. Westward and northward drift of the sea ice used by polar bears in both regions increased between 1987-1998 and 1999-2013. To remain within their home ranges, polar bears responded to the higher westward ice drift with greater eastward movements, while their movements north in the spring and south in fall were frequently aided by ice motion. To compensate for more rapid westward ice drift in recent years, polar bears covered greater daily distances either by increasing their time spent active (7.6%-9.6%) or by increasing their travel speed (8.5%-8.9%). This increased their calculated annual energy expenditure by 1.8%-3.6% (depending on region and reproductive status), a cost that could be met by capturing an additional 1-3 seals/year. Polar bears selected similar habitats in both periods, indicating that faster drift did not alter habitat preferences. Compounding reduced foraging opportunities that result from habitat loss; changes in ice drift, and associated activity increases, likely exacerbate the physiological stress experienced by polar bears in a warming Arctic.

Harvesting wildlife affected by climate change: a modelling and management approach for polar bears

The conservation of many wildlife species requires understanding the demographic effects of climate change, including interactions between climate change and harvest, which can provide cultural, nutritional or economic value to humans.We present a demographic model that is based on the polar bear Ursus maritimus life cycle and includes density-dependent relationships linking vital rates to environmental carrying capacity (K). Using this model, we develop a state-dependent management framework to calculate a harvest level that (i) maintains a population above its maximum net productivity level (MNPL; the population size that produces the greatest net increment in abundance) relative to a changing K, and (ii) has a limited negative effect on population persistence.Our density-dependent relationships suggest that MNPL for polar bears occurs at approximately 0·69 (95% CI = 0·63-0·74) of K. Population growth rate at MNPL was approximately 0·82 (95% CI = 0·79-0·84) of the maximum intrinsic growth rate, suggesting relatively strong compensation for human-caused mortality.Our findings indicate that it is possible to minimize the demographic risks of harvest under climate change, including the risk that harvest will accelerate population declines driven by loss of the polar bear's sea-ice habitat. This requires that (i) the harvest rate - which could be 0 in some situations - accounts for a population's intrinsic growth rate, (ii) the harvest rate accounts for the quality of population data (e.g. lower harvest when uncertainty is large), and (iii) the harvest level is obtained by multiplying the harvest rate by an updated estimate of population size. Environmental variability, the sex and age of removed animals and risk tolerance can also affect the harvest rate. Synthesis and applications. We present a coupled modelling and management approach for wildlife that accounts for climate change and can be used to balance trade-offs among multiple conservation goals. In our example application to polar bears experiencing sea-ice loss, the goals are to maintain population viability while providing continued opportunities for subsistence harvest. Our approach may be relevant to other species for which near-term management is focused on human factors that directly influence population dynamics within the broader context of climate-induced habitat degradation.

Habitat degradation affects the summer activity of polar bears

Understanding behavioral responses of species to environmental change is critical to forecasting population-level effects. Although climate change is significantly impacting species' distributions, few studies have examined associated changes in behavior. Polar bear (Ursus maritimus) subpopulations have varied in their near-term responses to sea ice decline. We examined behavioral responses of two adjacent subpopulations to changes in habitat availability during the annual sea ice minimum using activity data. Location and activity sensor data collected from 1989 to 2014 for 202 adult female polar bears in the Southern Beaufort Sea (SB) and Chukchi Sea (CS) subpopulations were used to compare activity in three habitat types varying in prey availability: (1) land; (2) ice over shallow, biologically productive waters; and (3) ice over deeper, less productive waters. Bears varied activity across and within habitats with the highest activity at 50-75% sea ice concentration over shallow waters. On land, SB bears exhibited variable but relatively high activity associated with the use of subsistence-harvested bowhead whale carcasses, whereas CS bears exhibited low activity consistent with minimal feeding. Both subpopulations had fewer observations in their preferred shallow-water sea ice habitats in recent years, corresponding with declines in availability of this substrate. The substantially higher use of marginal habitats by SB bears is an additional mechanism potentially explaining why this subpopulation has experienced negative effects of sea ice loss compared to the still-productive CS subpopulation. Variability in activity among, and within, habitats suggests that bears alter their behavior in response to habitat conditions, presumably in an attempt to balance prey availability with energy costs.

Increased Land Use by Chukchi Sea Polar Bears in Relation to Changing Sea Ice Conditions

Recent observations suggest that polar bears (Ursus maritimus) are increasingly using land habitats in some parts of their range, where they have minimal access to their preferred prey, likely in response to loss of their sea ice habitat associated with climatic warming. We used location data from female polar bears fit with satellite radio collars to compare land use patterns in the Chukchi Sea between two periods (1986–1995 and 2008–2013) when substantial summer sea-ice loss occurred. In both time periods, polar bears predominantly occupied sea-ice, although land was used during the summer sea-ice retreat and during the winter for maternal denning. However, the proportion of bears on land for > 7 days between August and October increased between the two periods from 20.0% to 38.9%, and the average duration on land increased by 30 days. The majority of bears that used land in the summer and for denning came to Wrangel and Herald Islands (Russia), highlighting the importance of these northernmost land habitats to Chukchi Sea polar bears. Where bears summered and denned, and how long they spent there, was related to the timing and duration of sea ice retreat. Our results are consistent with other studies supporting increased land use as a common response of polar bears to sea-ice loss. Implications of increased land use for Chukchi Sea polar bears are unclear, because a recent study observed no change in body condition or reproductive indices between the two periods considered here. This result suggests that the ecology of this region may provide a degree of resilience to sea ice loss. However, projections of continued sea ice loss suggest that polar bears in the Chukchi Sea and other parts of the Arctic may increasingly use land habitats in the future, which has the potential to increase nutritional stress and human-polar bear interactions.

Linking climate change projections for an Alaskan watershed to future coho salmon production

Climate change is predicted to dramatically change hydrologic processes across Alaska, but estimates of how these impacts will influence specific watersheds and aquatic species are lacking. Here, we linked climate, hydrology, and habitat models within a coho salmon (Oncorhynchus kisutch) population model to assess how projected climate change could affect survival at each freshwater life stage and, in turn, production of coho salmon smolts in three subwatersheds of the Chuitna (Chuit) River watershed, Alaska. Based on future climate scenarios and projections from a three-dimensional hydrology model, we simulated coho smolt production over a 20-year span at the end of the century (2080-2100). The direction (i.e., positive vs. negative) and magnitude of changes in smolt production varied substantially by climate scenario and subwatershed. Projected smolt production decreased in all three subwatersheds under the minimum air temperature and maximum precipitation scenario due to elevated peak flows and a resulting 98% reduction in egg-to-fry survival. In contrast, the maximum air temperature and minimum precipitation scenario led to an increase in smolt production in all three subwatersheds through an increase in fry survival. Other climate change scenarios led to mixed responses, with projected smolt production increasing and decreasing in different subwatersheds. Our analysis highlights the complexity inherent in predicting climate-change-related impacts to salmon populations and demonstrates that population effects may depend on interactions between the relative magnitude of hydrologic and thermal changes and their interactions with features of the local habitat.

Summer resource selection and identification of important habitat prior to industrial development for the Teshekpuk Caribou Herd in northern Alaska

Many caribou (Rangifer tarandus) populations are declining worldwide in part due to disturbance from human development. Prior to human development, important areas of habitat should be identified to help managers minimize adverse effects. Resource selection functions can help identify these areas by providing a link between space use and landscape attributes. We estimated resource selection during five summer periods at two spatial scales for the Teshekpuk Caribou Herd in northern Alaska prior to industrial development to identify areas of high predicted use for the herd. Additionally, given the strong influence parturition and insect harassment have on space use, we determined how selection differed between parturient and non-parturient females, and between periods with and without insect harassment. We used location data acquired between 2004–2010 for 41 female caribou to estimate resource selection functions. Patterns of selection varied through summer but caribou consistently avoided patches of flooded vegetation and selected areas with a high density of sedge-grass meadow. Predicted use by parturient females during calving was almost entirely restricted to the area surrounding Teshekpuk Lake presumably due to high concentration of sedge-grass meadows, whereas selection for this area by non-parturient females was less strong. When insect harassment was low, caribou primarily selected the areas around Teshekpuk Lake but when it was high, caribou used areas having climates where insect abundance would be lower (i.e., coastal margins, gravel bars). Areas with a high probability of use were predominately restricted to the area surrounding Teshekpuk Lake except during late summer when high use areas were less aggregated because of more general patterns of resource selection. Planning is currently underway for establishing where oil and gas development can occur in the herd’s range, so our results provide land managers with information that can help predict and minimize impacts of development on the herd.

Population genetic structure of the round stingray Urobatis halleri (Elasmobranchii: Rajiformes) in southern California and the Gulf of California

The round stingray, Urobatis halleri, is a viviparous elasmobranch that inhabits inshore, benthic habitats ranging from the western U.S.A. to Panama. The population genetic structure of this species was inferred with seven polymorphic microsatellite loci in samples collected at three sites in coastal southern California, one near Santa Catalina Island, California and one in the eastern Gulf of California. Urobatis halleri is relatively common, but little is known of its movement patterns or population structure. Small F(ST) values (-0.0017 to 0.0005) suggested little structure among coastal populations of southern and Baja California. The population sampled at Santa Catalina Island, which is separated by a deep-water channel from the coastal sites, however, was significantly divergent (large F(ST), 0.0251) from the other populations, suggesting low connectivity with coastal populations. The Santa Catalina Island population also had the lowest allele richness and lowest average heterozygosity, suggesting recent population bottlenecks in size.

Intra-abdominal vagal blocking (VBLOC therapy): clinical results with a new implantable medical device

BACKGROUND

A new medical device uses high-frequency electrical algorithms to create intermittent vagal blocking (VBLOC therapy). The aim is to assess the effects of vagal blocking on excess weight loss (EWL), safety, dietary intake, and vagal function.

METHODS

An open-label, 3-center study was conducted in obese subjects (body mass index [BMI] 35-50 kg/m(2)). Electrodes were implanted laparoscopically on both vagi near the esophagogastric junction to provide electrical block. Patients were followed for 6 months for body weight, safety, electrocardiogram, dietary intake, satiation, satiety, and plasma pancreatic polypeptide (PP) response to sham feeding. To specifically assess device effects alone, no diet or exercise programs were instituted.

RESULTS

Thirty-one patients (mean BMI, 41.2 +/- 1.4 kg/m(2)) received the device. Mean EWL at 4 and 12 weeks and 6 months after implant was 7.5%, 11.6%, and 14.2%, respectively (all P < .001); 25% of patients lost >25% EWL at 6 months (maximum, 36.8%). There were no deaths or device-related serious adverse events (AEs). Calorie intake decreased by >30% at 4 and 12 weeks and 6 months (all P <or= .01), with earlier satiation (P < .001) and reduced hunger (P = .005). After 12 weeks, plasma PP responses were suppressed (20 +/- 7 vs 42 +/- 19 pg/mL). Average percent EWL in patients with PP response <25 pg/mL was double that with PP response >25 pg/mL (P = .02). Three patients had serious AEs that required brief hospitalization, 1 each for lower respiratory tract, subcutaneous implant site seroma, and Clostridium difficile diarrhea.

CONCLUSIONS

Intermittent, intra-abdominal vagal blocking is associated with significant EWL and a desirable safety profile.

An isolated case of leprosy presenting in a migrant worker in Northern Ireland

Leprosy was first recorded in 600 bc in India. Europe saw its first cases in the fourteenth century. The worldwide incidence is falling, but the disease can still present in the most unexpected places: this is a report of the first case of leprosy presenting to an emergency department in Northern Ireland. It is important for physicians in both community and hospital medicine to have a high index of suspicion for leprosy in patients with chronic skin conditions who were born outside the UK or other developed countries.

Molecular characterization and expression of p63 isoforms in human keloids

Keloids are benign skin tumors that develop following wounding. A cDNA product from human keloid specimens was identified using the differential display technique. The full-length cDNA was cloned by RT-PCR using human keloid mRNA as template. The predicted product of the cDNA was found to be 99% identical to the DeltaN-p63 gamma isotype of p63, a transcription factor that belongs to the family that includes the structurally related tumor suppressor p53 and p73. The DeltaN-p63 isotype lacks the acidic N terminal region corresponding to the transactivation domain of p53. Since this can potentially block p53-mediated target gene transactivation, it may serve as a dominant-negative isoform. Real-Time RT-PCR analysis of RNAs from normal skin tissue and keloids showed that the DeltaN-p63 isotype is specifically expressed in keloids, but is virtually undetectable in normal skin. Immunostaining of p63 in normal skin revealed that only basal cells of the epithelium expressed the protein, while in keloid tissues the antigen was detected in the nuclei of cells scattered through all layers of the epithelium and in fibroblast-like cells in the dermis. These results may indicate that aberrant p63 expression plays a role not only in malignant tumors but also in benign skin diseases that show hyperproliferation of epidermal cells in vivo. Moreover, this isoform of p63 could serve as a specific molecular marker for this human disease.

A new species of Nezumia (Gadiformes: Macrouridae) from Fieberling Guyot, eastern North Pacific Ocean

A new species of the macrourine genus Nezumia is described from specimens collected from the crest of Fieberling Guyot in the eastern North Pacific Ocean. The new species is distinguishable from all other Nezumia species chiefly on the basis of a high number of pelvic fin rays, a relatively high number of first dorsal fin soft rays, a steep blunt snout lacking scales ventrally, a relatively weak suborbital ridge, and a moderately long, thin barbel. Although possibly endemic to the Baja California Seamount Province, the new species appears to lack close relatives among the other Nezumia species of the eastern North Pacific Ocean. It might have arrived there either from a disjunct Tethyan distribution, thus retaining close relatives among the Atlantic Ocean species of Nezumia, or by way of stepping-stone dispersal from the Indo-west Pacific Ocean.

Amphi-panamic geminates of snook (Percoidei: Centropomidae) provide a calibration of the divergence rate in the mitochondrial DNA control region of fishes

The mitochondrial DNA control region is one of the most frequently utilized sequences for both intra- and interspecific genetic studies of fishes, yet a tenable divergence rate specifically for fish control regions has not been established. We attempted to establish a rate through a comparative study of control region sequences and those of a protein-coding mitochondrial gene region from geminate species of snook (Centropomus) assumed to have been separated by the emergence of the Isthmus of Panama 3.5 million years ago. The divergence rate suggested from the control region alignments between the geminates was markedly higher than rates currently applied in many studies, as was the rate suggested from the ND 5/6 protein coding region alignments. However, the suggested ND 5/6 rate when applied to alignments with the outgroup species was not concordant with the scant centropomid fossil record and therefore the assumed separation time of 3.5 million years seemed implausible. An average control region divergence rate was then estimated based on separation times of snook species derived assuming a divergence rate of 1% per million years for transversion substitutions at third codon positions in the ND 5/6 region. Using these separation times, a tenable average divergence rate for fish control regions of approximately 3.6% per million years +/- 0.46% SE was calculated.

A cautionary note when using pepsin as a probe for the formation of a collagen triple helix

The ability of the collagen triple helix to resist digestion with proteases has been used as a conformational probe to ascertain whether a collagenous molecule has formed a correctly aligned helix during biosynthesis or during refolding of the protein in vitro. During our studies into the synthesis and folding of a variety of engineered procollagen polypeptide chains, we noted that resistance to digestion with proteases, in particular pepsin, could be misleading and does not necessarily indicate the formation of a collagen triple helix. These results clearly show that resistance to pepsin digestion alone should not be used to indicate correct folding and that preferably an alternative assay should be used to unequivocally demonstrate the formation of a correctly aligned triple helix.

Restriction digest of PCR-amplified mtDNA from fin clips is an assay for sequence genetic "tags" among hundreds of fish in wild populations

We tested the feasibility of recovering from wild populations mitochondrial DNA genetic "tags" that might result from release of hatchery-reared fingerlings for marine stock enhancement. A practical, nondestructive method of genetic "tag" recovery would allow quantitative assessment of the efficacy of such programs. A rare mtDNA variant with two sites each instead of one for TaqI and RsaI in the control region was used as a mock genetic "tag" in snook (Centropomus undecimalis). We assayed for the variant among nearly 900 fish by restriction digests of DNA amplified by polymerase chain reaction (PCR) obtained from fin-clip extracts, finding only a single second example of the variant. Thus, mtDNA "tags" can be nondestructively assayed for with specificity among hundreds of individuals.

The quality of life and employment in panic disorder

Our purpose was to measure quality of life (QOL) and work productivity (WP) in persons with panic disorder. Eighty-four panic disorder patients with limited psychiatric comorbidity for ten U.S. outpatient mental health centers were evaluated in a cross-sectional design. Patients self-administered the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36) and Work Productivity and Impairment (WPAI) questionnaire. The independent effects of psychiatric comorbidity were addressed through entry criteria, stratification, and regression analyses. QOL scores are significantly below age and sex-adjusted population norms on all SF-36 measures (p < .01). We note far greater impairment on measures of mental and emotional versus physical well-being. The unemployment rate among these patients is 25%, and only 57% are employed full-time. Those who are employed rated their WP as low. This sample of outpatients suffer marked QOL and employment impairment, which is only partially explained by the presence of psychiatric comorbidity.

Intermittent transdermal nitroglycerin therapy in angina pectoris. Clinically effective without tolerance or rebound. Minitran Efficacy Study Group

BACKGROUND

The objectives of this study were to assess the antianginal and anti-ischemic effects of three dose levels of transdermal nitroglycerin patches applied for 12 hours daily for 30 days. The study also assessed the development of tolerance and rebound. Intermittent transdermal nitroglycerin therapy with a patch-free period of 10 to 12 hours each day has documented clinical benefits during the period of patch application, but studies have failed to clearly document prolonged exercise duration for the entire period of patch application. This study was designed to evaluate the efficacy and duration of action of a range of doses of nitroglycerin. The study also permitted the assessment of the maintenance of initial effects, the development of tolerance, and the presence of rebound.

METHODS AND RESULTS

This study was a multicenter, randomized, double-blind, placebo-controlled parallel design trial with treadmill exercise tests at days 0, 1, 7, 15, and 30. Tests were carried out up to 12 hours after patch application. There was a statistically significant treatment effect with increases in treadmill walking time to moderate angina in each nitroglycerin patch group compared with placebo at various time points up to 12 hours throughout the 30-day study period. Secondary efficacy parameters, including the consistent increase in time to 1-mm ST-segment depression, supported the primary efficacy results. There was no evidence of tolerance or rebound.

CONCLUSIONS

Intermittent transdermal nitroglycerin therapy increases exercise duration and maintains anti-ischemic effects for 12 hours after patch application, throughout 30 days of therapy, without significant evidence of nitrate tolerance or rebound phenomena.

Salsalate cross-sensitivity in aspirin-sensitive patients with asthma

Ten aspirin (ASA)-sensitive patients with asthma underwent double-blind, placebo-controlled oral challenges with salsalate followed by ASA-sensitive confirmatory challenges. All 10 patients sustained asthmatic reactions to ASA, but only two developed respiratory reactions to 2 gm of salsalate. In these two patients, repeat confirmatory challenges with 2 gm of salsalate reproduced the same asthmatic reactions. Both patients were desensitized to ASA, and cross-desensitization with 2 gm of salsalate was then achieved. We conclude that salsalate, a weak inhibitor of cyclooxygenase in vitro, is less likely than ASA to induce asthma in known ASA-sensitive patients with asthma but may occasionally cross-react in these patients. Such reactions were mild and easily treated with beta 2-agonists.

Temperature adaptation of fish hemoglobins reflected in rates of autoxidation

Observation of rapid autoxidation of oxyhemoglobin (HbO2) from a deep-sea fish (Co-ryphaenoides acrolepis) prompted a survey of rates of autoxidation of HbO2 to methemoglobin in vitro from fishes inhabiting vastly different depths (1 to 3800 m) in order to discover any relationship between autoxidation rates and different environmental temperatures and pressures to which hemoglobins may be adapted. The rate of autoxidation was found to be sensitive to temperature in both deep- and shallow-living fishes. Hemoglobin appears to be thermally adapted since autoxidation was 10 times faster at all temperatures tested with HbO2 obtained from a cold-adapted fish (Coryphaenoides armatus variabilis) than from a comparatively warm-adapted one (Paralabrax nebulifer). High hydrostatic pressure does not affect autoxidation rates in either deep- or shallow-dwelling species. Rates of autoxidation may be intimately related to hemoglobin function thus providing a means for studying hemoglobin adaptation in poikilothermic vertebrates, especially among cold-adapted species.

Chymodiactin in patients with herniated lumbar intervertebral disc(s). An open-label, multicenter study

To extent the safety information for Chymodiactin (chymopapain for injection), 37 neurologic and orthopedic surgeons conducted an open-label, multicenter, phase 3 clinical study. A total of 1,498 patients with one or two herniated lumbar intervertebral discs were enrolled. Therapeutic results were generally favorable, with the percentages of patients achieving either excellent or good (or successful) results ranging from 79.6% to 88.9%, depending on criteria employed in the tabulation. There were 13 cases of anaphylaxis, and 2 of these patients died of complications of anaphylaxis. Two additional patients experienced serious neurologic problems. The first of these two patients developed transverse myelitis and paraplegia approximately 3 weeks following chemonucleolysis. Transdural discograms at three levels had been done approximately 2 days prior to chemonucleolysis, in violation of the protocol. The second patient developed acute cauda equina syndrome, and, despite emergency laminectomy, had permanent neurologic sequelae. Back spasm and stiffness/soreness were the most frequently encountered adverse experiences.