• Biogeochemical tracers of change in Pacific walruses past and present

      Clark, Casey; Horstmann, Lara; Misarti, Nicole; Konar, Brenda; Severin, Ken; Lemons, Patrick (2019-05)
      Reduced sea ice and projected food web shifts associated with warming of the Arctic have raised concerns about the future of Arctic species. Pacific walruses (Odobenus rosmarus divergens) use sea ice as a platform for molting, giving birth, and resting between foraging bouts. Exactly how sea ice loss will affect walruses is difficult to predict, due to a lack of information about regional ecosystems and their responses to climate change. The objectives of the research in this dissertation were to 1) examine how walrus diet changed in response to shifting sea ice conditions over the last 4,000 years, with the goal of generating predictions about how current and future ice loss may affect the walrus population; 2) make it easier to directly compare the results of retrospective and contemporary stable isotope studies of walruses; and 3) generate new tools to assist wildlife managers in monitoring the walrus population in an uncertain future. Stable carbon and nitrogen isotope ratios of walrus bone collagen indicated that diet was similar during previous intervals of high and low sea ice; however, diet variability among individual walruses was greater when sea ice cover was low, suggesting decreased abundance of preferred mollusk prey. Modern walrus diet was different from both previous high and low ice intervals, meaning that food webs in the Arctic are still in a state of flux, or that recent changes are novel within the last 4,000 years. Tissue-specific stable isotope discrimination factors were generated for walrus muscle, liver, skin, and bone collagen to improve comparisons between retrospective and contemporary studies of walrus diet. Additionally, lipid normalization models were parameterized for walrus skin and muscle, thereby making future walrus stable isotope research more feasible by reducing analytical costs and allowing the use of non-lethal sample collection. Finally, a novel technique for estimating the age at onset of reproductive maturity using concentrations of zinc and lead in the teeth of female walruses was established. This new approach has the potential to become a powerful tool for monitoring the walrus population and may be applicable to other species. Use of this technique on archived specimens may make it possible to examine changes in wildlife population dynamics across thousands of years.
    • Ecological effects of invasive European bird cherry (Prunus padus) on salmonid food webs in Anchorage, Alaska streams

      Roon, David A.; Wipfli, Mark; Prakash, Anupma; Wurtz, Tricia (2011-08)
      Invasive species are a concern worldwide as they can displace native species, reduce biodiversity, and disrupt ecological processes. European bird cherry (Prunus padus) (EBC) is an invasive ornamental tree that is rapidly spreading and possibly displacing native trees along streams in parts of urban Alaska. The objectives of this study were to: 1) map the current distribution of EBC along two Anchorage streams, Campbell and Chester creeks, and 2) determine the effects of EBC on selected ecological processes linked to stream salmon food webs. Data from the 2009 and 2010 field seasons showed: EBC was widely distributed along Campbell and Chester creeks; EBC leaf litter in streams broke down rapidly and supported similar shredder communities to native tree species; and EBC foliage supported significantly less terrestrial invertebrate biomass relative to native deciduous tree species, and contributed significantly less terrestrial invertebrate biomass to streams compared to mixed native vegetation, but riparian EBC did not appear to affect the amount of terrestrial invertebrate prey ingested by juvenile coho salmon (Oncorhynchus kisutch). Although ecological processes did not seem to be dramatically affected by EBC presence, lowered prey abundance as measured in this study may have long-term consequences for stream-rearing fishes as EBC continues to spread over time.
    • Energetics and space use of female moose during winter

      Kraft, Benjamin Robert; Hundertmark, Kris J.; Harris, Grant M.; Hunter, Christine M. (2011-05)
      Space use and resource selection are processes linked by habitat availability that have direct consequences to fitness. Knowledge of such processes allows comprehension of wildlife-habitat relationships, which can improve the efficacy of wildlife management programs. I investigated energetic and space use parameters of a population of female moose wintering in two adjacent, but distinct, landscape types (lowlands and mountains) on the Kenai Peninsula, AK, USA. I also evaluated differences between four home range models. I found that mountain females started winter in better condition, but used fat reserves at a higher rate than lowland females resulting in similar body condition estimates of moose in both landscape types in spring. I also found evidence of the functional response of habitat selection at the home range scale within landscape types. I observed a strong positive correlation between daily movement rate and home range size indicating that when females move during winter, they do so to access new areas expanding their home range. Brownian bridge, minimum convex polygon, fixed kernel, and local convex hull home range models produced different area and overlap estimates. Minimum convex polygons are least similar of model types and are not recommended to estimate areas actually used by animals.
    • Factors influencing chinook salmon spawning distribution in the Togiak River, Alaska

      Meggers, Stephanie L.; Seitz, Andrew; Prakash, Anupma; Lopez, Andres; Tanner, Theresa (2018-12)
      Salmonids are heavily dependent on specific habitat characteristics for survival, yet few studies in Alaska have examined the relationship between habitat and spawning distribution, using remote sensing approaches. To better understand the relationship between Chinook Salmon Oncorhynchus tshawytscha spawning distribution and environmental variables like habitat type (e.g., run, riffle, pool), temperature, and proximity to channel islands, optical and thermal imagery were collected on the Togiak and Ongivinuk rivers in southwest Alaska. Object-based image analysis was used to classify and quantify habitat types, while thermal characteristics and the proximity of spawning locations to channel islands were determined in a GIS framework. Object-based image analysis was useful for classifying habitat and may provide a better alternative to pixel-based image analysis. However, rule sets were nontransferable and inconsistent among river reaches, and caution should be taken when these methods are used on large river sections. Chinook Salmon showed a preference for spawning in river runs, 80% of fish spawned in water temperatures between 8.6° and 9.4°C, and nearly 61% of Chinook Salmon spawned within 100 m of a channel island. This study provided a baseline understanding of environmental correlates of spawning for Chinook Salmon at the northern extent of their range.
    • Multi-scale movement of demersal fishes in Alaska

      Nielsen, Julie K.; Seitz, Andrew C.; Loher, Timothy; McDermott, Susanne F.; Mueter, Franz J.; Adkison, Milo D. (2019-05)
      Information on the movement of migratory demersal fishes such as Pacific halibut, Pacific cod, and sablefish is needed for management of these valuable fisheries in Alaska, yet available methods such as conventional tagging are too coarse to provide detailed information on migration characteristics. In this dissertation, I present methods for characterizing seasonal and annual demersal fish movement at multiple scales in space and time using electronic archival and acoustic tags. In Chapter 1, acoustic telemetry and the Net Squared Displacement statistic were used to identify and characterize small-scale movement of adult female Pacific halibut during summer foraging in a Marine Protected Area (MPA). The dominant movement pattern was home range behavior at spatial scales of less than 1 km, but a more dispersive behavioral state was also observed. In Chapter 2, Pop-up Satellite Archival Tags (PSATs) and acoustic tags were deployed on adult female Pacific halibut to determine annual movement patterns relative to MPA boundaries. Based on observations of summer home range behavior, high rates of year-round MPA residency, migration timing that largely coincided with winter commercial fisheries closures, and the demonstrated ability of migratory fish to return to previously occupied summer foraging areas, the MPA is likely to be effective for protecting both resident and migrant Pacific halibut brood stock year-round. In Chapter 3, I adapted a Hidden Markov Model (HMM) originally developed for geolocation of Atlantic cod in the North Sea for use on demersal fishes in Alaska, where maximum daily depth is the most informative and reliable geolocation variable. Because depth is considerably more heterogeneous in many regions of Alaska compared to the North Sea, I used simulated trajectories to determine that the degree of bathymetry heterogeneity affected model performance for different combinations of likelihood specification methods and model grid sizes. In Chapter 4, I added a new geolocation variable, geomagnetic data, to the HMM in a small-scale case study. The results suggest that the addition of geomagnetic data could increase model performance over depth alone, but more research is needed to continue validation of the method over larger areas in Alaska. In general, the HMM is a flexible tool for characterizing movement at multiple spatial scales and its use is likely to enrich our knowledge about migratory demersal fish movement in Alaska. The methods developed in this dissertation can provide valuable insights into demersal fish spatial dynamics that will benefit fisheries management activities such as stock delineation, stock assessment, and design of space-time closures.
    • Novel fungal taxa in an Alaskan boreal forest: phylogenetic affinities, ecologies, and ribosomal RNA secondary structures

      Glass, Daniel; Taylor, D. Lee; Olson, Link E.; Takebayashi, Naoki; Duffy, Lawrence (2011-12)
      Phylogenetic analyses suggest that a novel DNA sequence (NS1) found in a boreal forest soil-clone library belongs to the fungal kingdom but does not fall unambiguously within any known class. In order to determine if NS1 codes for an authentic ribosomal RNA (rRNA) gene-copy, I modeled ribosomal RNA secondary structure for four gene regions. Such analyses have never been used on environmental ribosomal sequences before. It appears that NS1 does code for an authentic gene-copy and is not a biological or lab artifact. I also elucidated the habitat preferences, horizon preferences, and fine-scale spatial structure of NS1 using molecular methods. I determined that NS1 was associated with spruce and was found in both the organic and mineral soil horizons. It appears to have a clumped distribution on the scale of a few meters and its spatial distribution shows little inter-annual variability. Together these findings suggest that NS1 does represent an authentic gene-copy and also shed light on the ecology of this putative taxon. I hope future efforts will expand our understanding of both its identity and function.
    • Population ecology of willow ptarmigan (Lagopus lagopus) in the presence of spatially concentrated harvest

      Frye, Graham G.; Lindberg, Mark; Brainerd, Scott; Kielland, Knut; Schmidt, Joshua (2020-05)
      Understanding the potential effects of harvest on wildlife populations is fundamental to both theoretical wildlife science and applied wildlife management. The effects of harvest on wildlife populations vary dramatically and depend on the timing and magnitude of harvest, as well as population-specific states and vital rates. Demographic compensation plays a key role in models of wildlife population dynamics and in developing harvest strategies. However, the degree and form of compensation in a given population depends on its particular ecological and life history characteristics, resulting in the need for population-specific assessments of responses to harvest. Ptarmigan (Lagopus spp.) are ecologically important species and are culturally valued for subsistence and recreational hunting throughout the Holarctic. In Alaska, willow ptarmigan (L. lagopus) are among the most commonly harvested small game species, but the population-level effects of harvest are not well understood. Investigating the population level effects of harvest on these populations would aid harvest management and increase general understanding of the ecology of the species. To this end, I studied the population ecology of willow ptarmigan in a region of Alaska with spatially concentrated harvest along access corridors. I investigated: (1) the effect of harvest, season, and demographic group on survival, (2) the effect of harvest on breeding densities, (3) dispersal and seasonal movements patterns in relation to harvest, and (4) temporal and observer effects on ptarmigan survey efforts. I found that survival rates and breeding densities of willow ptarmigan in heavily hunted areas were substantially lower than those in remote sites without hunting. We did not observe seasonal compensatory mortality and the potential for permanent immigration (i.e., breeding/natal dispersal) to compensate for harvest appeared limited. However, seasonal movements away from breeding territories appeared to distribute the effects of harvest more evenly among ptarmigan from accessible and remote areas during winter and early spring. This suggests that the timing of hunting seasons may play a critical role in determining effects on ptarmigan densities in accessible breeding areas, with early autumn (prior to initiation of seasonal movements) harvest likely having the greatest impact. In addition, when examining ptarmigan survey methodology, I found substantial temporal heterogeneity in the availability of ptarmigan for detection during surveys, as well as variation in observer-specific detection rates. This underscores the importance of investigators considering the role of imperfect and heterogeneous detection when designing ptarmigan monitoring strategies to avoid inaccurate conclusions about abundance and trends.
    • The seasonal dynamics of coastal Arctic lagoons in Northwest Alaska

      Tibbles, Marguerite; Seitz, Andrew C.; Falke, Jeffrey A.; Prakash, Anupma; Robards, Martin D. (2018-12)
      Lagoons are zones of habitat transitions between freshwater and marine ecosystems, providing safe and productive feeding habitats for whitefishes in Northwest Alaska, important to subsistence users in the region. However, many important lagoon processes are not understood. Therefore, the goal of this thesis was to gain a baseline understanding of two important seasonal processes of lagoons in Northwest Alaska. First, I attempted to identify environmental processes correlated with Arctic lagoon breaching for three indicator lagoons that represent a range of environmental characteristics using generalized linear models (GLM) in an information theoretic approach and model averaging. Second, I developed a habitat suitability (HS) model to identify the range of physical conditions that whitefishes may experience if overwintering under ice of these lagoons during the Arctic winter, for the same three lagoons. The GLM model suggested that lagoon breaching day of year was slightly negatively related to day of year of river break-up, but other unconditional confidence intervals for the covariate parameters overlapped zero indicating considerable uncertainty in these estimates. Further data collection and monitoring in the region is needed to improve and verify lagoon breaching modelling results. The HS model indicated that lagoons have reduced suitability as whitefish habitat in winter due to loss of habitat due to the presence of bottomfast ice and a reduction of liquid water quality due to cold temperatures, high salinities and low dissolved oxygen levels. Importantly, small lagoons without freshwater inputs were potential sinks for fish populations. The results from this research will help the National Park Service and the Native Village of Kotzebue in a joint effort to understand and manage these important habitats that are critical for subsistence fisheries as the Arctic faces an uncertain future with climate change, oil spill threats, and increased coastal development.
    • Spatial variation in blueberry (Vaccinium uliginosum) and lingonberry (Vaccinium vitis-idaea) fruit production in Interior Alaska

      Parkinson, Linsey Viann; Mulder, Christa; Hollingsworth, Teresa; Spellman, Katie (2019-05)
      There are over 50 species of plants in Alaska that produce fleshy fruits (hereafter: "berries"), of which people consume 25. Berries are a key cultural and nutritional resource in rural Alaska and an important source of calories for a range of animals including bears (Ursus spp.), foxes (Vulpes vulpes), geese (e.g., Branta hutchinsii), and voles (e.g., Myodes rutilus). Berry production, from bud development to ripe fruit, takes at least 15 months and may be affected by factors even a year or two before that. Many studies in the circumpolar North focus on these interannual effects on fruit production but few assess how local variation within a forested region may affect berry numbers. Changes in the frequency and severity of wildfires in the boreal forest has affected soil conditions and plant community structure, which may alter the range of circumstances a species must respond to, influencing overall fruit production at a site. I studied how fruit production in Vaccinium uliginosum (blueberry) and V. vitis-idaea (lingonberry), responded to factors such as pollen load, floral resources, canopy cover, and soil conditions within forest sites of Interior Alaska. I found two distinct habitat types in the Interior Alaskan forest, upland and lowland, which differed by elevation, soil moisture (lower in upland sites), and active layer (deeper in upland sites). We found lingonberry was more pollen limited than blueberry, and plants in lowland sites were more pollen limited while plants in upland sites were more resource limited. Additionally, canopy cover had a significant negative effect on a ramet's investment in flowers, berries, and leaves, versus structural growth, in upland sites but little effect in lowland sites. I was able to explain more of the variation in berry production and resource allocation in upland sites than lowland sites. Pollen and resource limitation differed between the two species and between uplands and lowlands suggesting Vaccinium berry production and resource allocation is partially defined by spatial variability of the landscape.
    • The use of aerial imagery to map in-stream physical habitat related to summer distribution of juvenile salmonids in a Southcentral Alaskan stream

      Perschbacher, Jeff; Margraf, F. Joseph; Hasbrouck, James; Wipfli, Mark; Prakash, Anupma (2011-12)
      Airborne remote sensing (3-band multispectral imagery) was used to assess in-stream physical habitat related to summer distributions of juvenile salmonids in a Southcentral Alaskan stream. The objectives of this study were to test the accuracy of using remote sensing spectral and spatial classification techniques to map in-stream physical habitat, and test hypotheses of spatial segregation of ranked densities of juvenile chinook salmon Oncorhynchus tschwytscha, coho salmon O. kisutch, and rainbow trout O. mykiss, related to stream order and drainage. To relate habitat measured with remote sensing to fish densities, a supervised classification technique based on spectral signature was used to classify riffles, non-riffles, vegetation, shade, gravel, and eddy drop zones, with a spatial technique used to classify large woody debris. Combining the two classification techniques resulted in an overall user's accuracy of 85%, compared to results from similar studies (11-80%). Densities of juvenile salmonids was found to be significantly different between stream orders, but not between the two major drainages. Habitat data collected along a 500-meter stream reach were used successfully to map in-stream physical habitat for six river-kilometers of a fourth-order streams. The use of relatively inexpensive aerial imagery to classify in-stream physical habitats is cost effective and repeatable for mapping over large areas, and should be considered an effective tool for fisheries and land-use managers.