• The effects of permafrost degradation on soil carbon dynamics in Alaska's boreal region

      O'Donnell, Jonathan A. (2010-12)
      High-latitude regions store large quantities of organic carbon (C) in permafrost soils and peatlands, accounting for nearly half of the global belowground C pool. Projected climate warming over the next century will likely drive widespread thawing of near-surface permafrost and mobilization of soil C from deep soil horizons. However, the processes controlling soil C accumulation and loss following permafrost thaw are not well understood. To improve our understanding of these processes, I examined the effects of permafrost thaw on soil C dynamics in forested upland and peatland ecosystems of Alaska's boreal region. In upland forests, soil C accumulation and loss was governed by the complex interaction of wildfire and permafrost. Fluctuations in active layer depth across stand age and fire cycles determined the proportion of soil C in frozen or unfrozen soil, and in turn, the vulnerability of soil C to decomposition. Under present-day climate conditions, the presence of near-surface permafrost aids C stabilization through the upward movement of the permafrost table with post-fire ecosystem recovery. However, sensitivity analyses suggest that projected increases in air temperature and fire severity will accelerate permafrost thaw and soil C loss from deep mineral horizons. In the lowlands, permafrost thaw and collapse-scar bog formation resulted in the dramatic redistribution of soil water, modifying soil thermal and C dynamics. Water impoundment in collapse-scar bogs enhanced soil C accumulation in shallow peat horizons, while allowing for high rates of soil C loss from deep inundated peat horizons. Accumulation rates at the surface were not sufficient to balance deep C losses, resulting in a net loss of 26 g C m⁻² y⁻¹ from the entire peat column during the 3000 years following thaw. Findings from these studies highlight the vulnerability of soil C in Alaska's boreal region to future climate warming and permafrost thaw. As a result, permafrost thaw and soil C release from boreal soils to the atmosphere should function as a positive feedback to the climate system.
    • Effects of recreational disturbance on breeding black oystercatchers: species resilience and conservation implications

      Morse, Julie Anne (2005-12)
      The potential conflict between increasing recreational activities and nesting birds in coastal habitats has raised concerns about the conservation of the black oystercatcher (Haematopus bachmani). To address these concerns, I studied the breeding ecology of black oystercatchers in Kenai Fjords National Park and examined the impact of recreational disturbance on breeding parameters. Most recreational disturbance of breeding territories was from kayak campers and occurred after June 13, the peak hatch of first clutches. Mean annual fledging success (24%) was low, but the results suggest that daily survival rates of nests and broods did not differ between territories with and without recreational disturbance. Nest survival varied annually and seasonally, and declined during periods of extreme high tides. Daily survival rate of broods was higher on island territories than mainland territories, presumably due to differences in predator communities. Most (95%) color-banded oystercatchers returned to their breeding territories in the subsequent year regardless of level of disturbance. On average, black oystercatchers decreased incubation constancy by 39% in response to experimental disturbance. However, I found no evidence that time off the nest was associated with probability of nest survival. Further, I found no evidence that oystercatchers habituated to recreational activity. The data suggest that black oystercatchers in Kenai Fjords National Park are resilient to the current low levels of recreational disturbance.
    • Effects of sample size and ageing error on estimates of sustained yield

      Coggins, Lewis G.; Quinn, Terrance J. II; Hasbrouck, James J.; Haldorson, Lewis J.; Reynolds, James B. (1997-12)
      A Monte Carlo simulation model of an exploited age-structured fish population was constructed, to evaluate the effects of sampling and ageing the catch on estimates of population parameters from catch-age analysis with auxiliary information and resultant estimates of sustained yield. A factorial experimental design was used where input parameters were varied among: small (100), medium (300) and large (900) catch sample sizes; high and low levels of ageing precision; and a range of ageing biases. Ageing bias and precision had dramatic effects on estimated sustained yield: positive ageing bias and ageing imprecision generally caused under-estimation of sustained yield, while negative ageing bias caused over-estimation of sustained yield. The multiple reader/reading ageing scenarios designed to mitigate ageing error were able to reduce the affects of ageing imprecision, but were unable to alleviate the problems associated with ageing bias. The simulation model can be modified for a variety of recreational fish populations; a diskette and user manual are available.
    • Environmental and evolutionary processes affecting population dynamics and life-history of arctic grayling in western and Interior Alaska

      Neyme, Jenny Lou (2005-08)
      I compared the life-history and population dynamics of arctic grayling Thymallus arcticus in western and Interior Alaska. Fish in western Alaska grew rapidly to a large maximum size, adult mortality rates were low and juvenile mortality rates were high. As a result, western populations consisted mainly of larger, older fish. Fish in Interior streams grew more slowly to a smaller maximum size, adult mortality rates were higher and juvenile mortality rates lower than in western streams. As a result, Interior populations consisted mainly of smaller, younger fish. The relationship between body size and ovary mass was similar between regions, but Interior fish allocated a greater proportion of their annual energy budget to reproduction. I also used a foraging model to test the hypothesis that regional differences in drift-feeding opportunities were responsible for faster growth and larger size in arctic grayling in western Alaska and to determine the relative contribution of invertebrate drift density and physical habitat characteristics to regional differences in profitability. The model predicted that drift-feeding would be more profitable in western Alaska and that regional differences in invertebrate drift density and size composition were responsible for this difference.
    • Environmental drivers of deer population dynamics and spatial selection in Southeast Alaska

      Gilbert, Sophie L.; Hundertmark, Kris; Boyce, Mark; Lindberg, Mark; Person, David (2015-08)
      The coastal temperate rainforest is one of the rarest ecosystems in the world, and a major portion of the global total is found in Southeast Alaska. In this ecosystem, Sitka black-tailed deer are the dominant large herbivore, influencing large carnivores that prey on deer such as wolves and bears, as well as plant species and communities through browsing. In addition, deer play an important economic and cultural role for humans in Southeast Alaska, making up the large majority of terrestrial subsistence protein harvested each year as well as providing the backbone of a thriving tourism industry built around sport hunting. Given the importance of deer in this system, there remain a surprisingly large number of key gaps in our knowledge of deer ecology in Southeast Alaska. These knowledge gaps are potentially troubling in light of ongoing industrial timber-harvest across the region, which greatly alters habitat characteristics and value to wildlife. This dissertation research project was undertaken with the aim of filling several connected needs for further understanding deer ecology, specifically 1) patterns of reproduction and fawn survival, 2) population dynamics in response to environmental variability, and the underlying drivers of spatial selection during 3) reproduction and 4) winter. To fill these knowledge gaps, I developed robust statistical tools for estimating rates of fawn survival, and found that fawns must be captured at birth, rather than within several days of birth, in order to produce unbiased estimates because highly vulnerable individuals died quickly and were thus absent from the latter sample. I then use this robust approach to estimate vital rates, including fawn survival in winter and summer, and developed a model of population dynamics for deer. I found that winter weather had the strongest influence on population dynamics, via reduced over-winter fawn survival, with mass at birth and gender ratio of fawns important secondary drivers. To better understand deer-habitat relationships, I examined both summer and winter habitat selection patterns by female deer. Using summer-only data, I asked how reproductive female deer balance wolf and bear predation risk against access to forage over time. Predation risks and forage were strong drivers of deer spatial selection during summer, but reproductive period and time within reproductive period determined deer reaction to these drivers. To ensure adequate reproductive habitat for deer, areas with low predation risk and high forage should be conserved. Focusing on winter, I evaluated deer spatial selection during winter as a response to snow depth, vegetation classes, forage, and landscape features. I allowed daily snow depth measures to interact with selection of other covariates, and found strong support for deer avoidance of deep snow, as well as changes in deer selection of old-growth and second-growth habitats and landscape features with increasing snow depth. Collectively, this dissertation greatly improves our understanding of deer ecology in Alaska, and suggests habitat management actions that will help ensure resilient deer populations in the future.
    • Estimation of abundance and mortality of emigrating chum salmon and chinook salmon in the Chena River, Alaska

      Peterson, Brent David (1997-05)
      During May-June, 1995 and 1996, the outmigration of juvenile chum salmon (Oncorkynchus keta) and chinook salmon (O. tschazvytscha) was sampled with floating traps in the area of the Chena River Lakes Flood Control Project, Chena River, Alaska. Catch-per-unit-effort (CPUE) was higher at night than day for chinook juveniles, but not for chum juveniles. CPUE of both species decreased as the season progressed, but usually increased during higher-discharge events. CPUE is standardized by time; discharge was monitored as a covariate but was not included in CPUE calculations. The Jolly-Seber family of models was used on recapture data of fin-dipped fish to obtain estimates of abundance and survival in 1996. Abundance estimates were 266,104 chum salmon (95% Cl 128,031 - 404,177) and 171,952 chinook salmon (95% Cl 146,342 - 197,561) during the May-June outmigration period. These abundance estimates are probably underestimates of the entire Chena River population. Survival estimates were 0.135 (95% Cl 0.042 - 0.228) for chum salmon and 0.713 (95% Cl 0.492 - 0.935) for chinook salmon over the same period.
    • Evaluating the hooking injury and immediate physiological response of wild rainbow trout to capture by catch-and-release angling

      Meka, Julie M. (2003-08)
      Rainbow trout from the Alagnak River watershed, Alaska, were captured by angling to determine the types of terminal gear contributing to hooking injury and the physiological response to angling based on concerns over high incidences of hooking injuries and the physiological impact of multiple recaptures on individual fish. Landing and hook removal times were recorded for a portion of fish captured, and plasma cortisol, glucose, ions (sodium, chloride, potassium), and lactate were evaluated in fish following capture to document physiological changes in relation to capture duration. The majority of new injuries resulted when fish were captured using barbed J hooks, and barbed J hooks took longer to remove than barbless hooks. Fish were hooked internally more frequently when captured with J hooks compared to circle hooks, but similar overall hooking injury rates were observed for both hook types. Novice anglers injured proportionally more fish than experienced anglers, and experienced anglers took longer to land fish than novice anglers. Plasma cortisol and lactate increased significantly with increasing landing and handling times. Fish captured at cooler water temperatures had significantly lower cortisol and lactate concentrations than fish caught at warmer temperatures indicating that water temperature influenced the magnitude of the physiological response.
    • Evaluation of wolf density estimation from radiotelemetry data

      Burch, John W. (2001-05)
      Density estimation of wolves (Canis lupus) requires a count of individuals and an estimate of area those individuals inhabit. With radiomarked wolves, the count is straightforward but estimation of area is more difficult and often given inadequate attention. The population area, based on the mosaic of pack territories, is influenced by sampling intensity similar to individual home ranges. If sampling intensity is low, population area will be underestimated and wolf density will be inflated. Using data from studies in Denali National Park and Preserve, I investigated these relationships using Monte Carlo simulation to evaluate effects of radiolocation effort and number of marked packs on density estimation. As the number of adjoining pack home ranges increase, fewer relocations are necessary to define a given percentage of population area. I evaluated the utility of nonlinear regression to adjust for biases associated with under sampling and present recommendations for monitoring wolves via radiotelemetry.
    • Factors affecting body mass of prefledging emperor geese

      Lake, Bryce Cameron (2005-08)
      Body mass of pre fledging geese has important implications for fitness and population dynamics. To address whether interspecific competition for forage was broadly relevant to prefledging emperor geese, I investigated the factors affecting body mass at three locations across the Yukon-Kuskokwim Delta, Alaska. From 1990 - 2004, densities of cackling geese more than doubled and were 2-5x higher than densities of emperor geese, which were relatively constant over time. During 2003 - 2004, body mass of emperor geese increased with net above-ground primary productivity (NAPP) and grazing lawn extent and declined with interspecific densities of geese (combined density of emperor and cackling geese). Grazing by geese resulted in consumption of 90% of the NAPP that occurred during the brood rearing period, suggesting that interspecific competition was due to exploitation of common food resources. At six sampled locations, grazing lawn extent varied among- and within-locations, and was stable or declined slightly during 1999-2004, indicating reduced per capita availability. I conclude that negative effects of interspecific goose densities on body mass of pre fledging geese are partially responsible for recent declines in the fall age ratio of emperor geese because of a positive correlation between body mass and survival to fall staging areas. Management to increase the population size of emperor geese should consider interspecific densities of geese and interactions between interspecific densities and forage.
    • Feeding ecology of black oystercatcher (Haematopus bachmani) chicks

      Robinson, Brian H.; Powell, Abby; O'Brien, Diane; Konar, Brenda (2016-05)
      The Black Oystercatcher is an internationally recognized bird species of conservation concern and the focus of multiple monitoring programs due its small global population size, restricted range, vulnerability to human and natural threats in nearshore marine ecosystems, and the important role it plays as a top-level consumer in the intertidal food web. I studied a population of Black Oystercatchers in Kenai Fjords National Park, Alaska in 2013 and 2014, examining variation in chick diet, assessing methods used to monitor diet, and investigating the influence of provisioning on brood survival. To better understand the biases and limitations associated with the quantification of prey remains, I compared diet estimates from prey remains with two other methods: direct observation of adults feeding young, and diet reconstruction by stable isotope analysis. Estimates from collected prey remains over-represented the proportion of limpets in the diet, under-represented the proportion of mussels and barnacles, and failed to detect soft-bodied prey such as worms. I examined age- and habitat-specific variation in chick diet and found no relationship between diet and age of chicks; however, diet differed between gravel beach and rocky island nesting habitats. To determine the importance of diet on brood survival, I modeled daily survival rates of broods as a function of energy intake rate and other ecological factors and found that broods with higher intake rates had higher growth rates and daily survival rates. Given the consequences of reduced energy intake on survival, changes in the abundance and composition of intertidal macroinvertebrates as a result of climate change may have significant impacts on Black Oystercatcher populations. These findings highlight the importance of diet and provisioning to chicks and identify limitations of using prey remains to characterize Black Oystercatcher diet.
    • Foods and foraging ecology of oldsquaws (Clangula hyemalis L.) on the arctic coastal plain of Alaska

      Taylor, Eric John (1986-09)
      The study was conducted from June to September during 1979 and 1980 in the the West Long Lake area of the National Petroleum Reserve-Alaska. Additional oldsquaws were collected in the inland wetlands near the northwest boundary of the reserve at Ice Cape. West Long Lake and the adjacent Goose Lake are located 15 miles south of the Beaufort Sea and immediately west of Teshekpuk Lake.
    • Foraging behavior of caribou on a calving ground in northwestern Alaska

      Kuropat, Peggy JoAnn (1984-12)
      Habitat selection, foraging behavior, and forage intake rates by caribou were studied on a calving ground in northwestern Alaska. The pattern of emergence of new plant growth determined habitat use. The grazing pattern reflected a balance between selection for nutrients and plant biomass, and avoidance of plant secondary metabolites. Habitat use was also influenced by predator avoidance. At the time of calving, meteorological conditions provide a snow-free "window" of available Eriophorum vaginatum inflorescences that are of high nutritive value. Subsequently, topographic variation results in a diversity of forbs and shrubs confined in time and space at the time of peak nutritional demands for lactation and growth of calves during June. Intake of deciduous shrub leaves averaged 3.7 g/min and the intake of E. vaginatum inflorescences was 1.1 g/min. Highest observed intake was 5.5 g/min on forbs. Forage selected was of high nutritive value and high digestibility. Thus, caribou selected productive microsites and habitats where intake of preferred forage could be maximized.
    • Genetic variation in muskoxen (Ovibos moschatus)

      Fleischman, Claire L. (1986-05)
      Populations of Alaskan muskoxen (Ovibos moschatus) are derived from 34 animals transplanted from East Greenland in the 1930s. The possibility of a founder effect following this transplant was investigated. Muscle, liver and plasma samples from 87 Alaskan animals and 39 Greenlandic animals were analyzed using polyacrylamide and starch gel electrophoresis. A total of 38 enzyme and non-enzymatic protein systems, coded by 58 presumptive loci, was tested for activity; 28 loci were considered usable. One locus (Esterase-2) was polymorphic; the proportion of polymorphic loci was 0.036 (95% criterion). The mean heterozygosity per individual was 0.006 in the Greenlandic population and 0.011 in the Alaskan population. The allele frequencies at the Est-2 locus were similar in both populations. No heterozygote deficiency and no evidence of a founder effect were seen in the Alaskan population. This may be a consequence of the low level of allozymic variation seen in muskoxen in general.
    • Geomorphology and inconnu spawning site selection: an approach using GIS and remote sensing

      Tanner, Theresa Lynn; Margraf, T. Joseph; Wipfli, Mark S.; Verbyla, David (2008-08)
      This study examined the spatial components of inconnu Stenodus leucichthys spawning habitat use in the Selawik River, Alaska. Little is known about inconnu critical habitat needs; however, current studies of inconnu spawning behavior suggest a high level of habitat selectivity. This level of selectivity implies that there are specific habitat characteristics that these fish require for spawning. The purpose of this study was to build a heuristic habitat model that can be used to better understand inconnu spawning site selection in remote Alaskan watersheds. Using readily available, low- or no-cost remote sensing data layers, geographical information systems (GIS) were used in conjunction with multivariate statistics in an attempt to clarify relationships between geomorphologic features and spawning site selection. Spatial resolution of the remotely sensed data available in this study did not provide sufficient spatial detail to generate statistical correlations between spawning habitat selection and landscape characterizations. However, spawning occurred in areas of transition from high to low gradients, and in reaches typified as having very low slopes with very high sinuosity. Additionally, exploratory use of Radarsat fine beam 1 data favored its future application in fisheries investigations. This study is an initial step toward more research into inconnu spawning habitat.
    • Growth and Energetic Condition of Dolly Varden Char in Coastal Arctic Waters

      Stolarski, Jason T.; Prakash, Anupma; Sutton, Trent; Margraf, Joseph; Rosenberger, Amanda (2013-05)
      Dolly Varden char Salvelinus malma are a dominant member of the nearshore Arctic icthyofauna and support one of the largest subsistence fisheries within Arctic coastal communities in Alaska. Despite this importance, numerous aspects of Dolly Varden ecology remain poorly understood, which inhibits efforts to assess the biological consequences of anthropogenic disturbances such as hydrocarbon extraction and climate change within nearshore areas. The goal of this research was to develop and apply new techniques to measure and assess the biological integrity of Dolly Varden populations. To do so, I evaluated the precision of age determination generated from scales, otoliths, and fin rays, developed and validated bioelectrical impedance analysis (BIA) models capable of predicting non-lethal estimates of Dolly Varden proximate content, calculated and correlated retrospective estimates of Dolly Varden growth from archived otolith samples to broad-scale environmental variables, and investigated trends in whole body and tissue proximate content among years and demographics (i.e. reproductive versus non-reproductive individuals). Dolly Varden age determinations can be produced non-lethally using scales for fish up to age 5, while otoliths should be used for fish age 6 and greater. Multi-surface BIA models produced estimates of whole body proximate content with high precision. Retrospective growth analyses indicated growth increased significantly during the early 1980s, and was positively correlated to air temperature, sea surface temperature, and discharge and negatively correlated to ice concentration. Analyses of proximate content suggested that non-reproductive fish contained greater lipid concentrations than reproductive fish. Growth and condition analyses suggest that these metrics vary among years and are a function of reproductive cycles and environmental variability operating at multiple temporal and spatial scales. The adoption of scale-based aging and BIA technology will increase the precision of age-based biological statistics and aid in the detection of change within future Dolly Varden research and monitoring.
    • Growth and maturity of the Pacific razor clam in eastern Cook Inlet, Alaska

      McKellar, Jamie M.; Sutton, Trent; Iken, Katrin; Horstmann-Dehn, Lara; Hardy, Sarah; Erickson, Jack (2014-12)
      In Alaska, the only road-accessible fishery for the Pacific razor clam, Siliqua patula, is located in eastern Cook Inlet, and has been monitored by the Alaska Department of Fish & Game (ADF&G) since 1964. In recent years, a shift has been observed in size, age, and number of clam cohorts in this region, yet little is known about the early life history of razor clams in this region. This study aimed to provide information on length and age at maturity, growth rates, and spawn timing at two beaches in eastern Cook Inlet, Ninilchik and Clam Gulch, in 2009 and 2010. At Clam Gulch, only 20% of the sampled population was reproductive, compared with 83% at Ninilchik. At Ninilchik, clams were reproductive at a smaller size and younger age (p<0.05) than previously documented. The Ninilchik clams grew faster and had a larger size at age (p<0.05) than at Clam Gulch. A body condition index of clams from Clam Gulch was consistently 50% lower than at Ninilchik. Despite the relative proximity (25 km) of these locations, it is possible that environmental conditions may be different, resulting in differences in growth and reproductive output. This information is of special interest to fisheries managers as they address recent declines in the eastern Cook Inlet razor clam population and provides a benchmark for future management decisions.