• 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.
    • The use of aspect in a Gwich'in narrative

      Richards, Qwynten Daelgar (2004-05)
      This work is an investigation of the role of viewpoint aspect in highlighting and fore grounding information in discourse, and in structuring narrative discourse within a Gwich'in narrative. The purpose is to contribute to a clearer understanding of how aspect functions cross-linguistically. The focus of the analysis is on the perfective/imperfective contrast which involves speaker choice. The findings are that there is an interesting correlation between shift in narrative episode and shift in viewpoint aspect, and additionally, that the use of the perfective does highlight and mark significant information in the narrative. The study also examines the narrative in terms of proposed universals in narrative structure, as outlined by Labov, but does not find enough evidence to support his claims in Gwich'in.
    • Use of Beaufort Sea as feeding habitat by bowhead whales (Balaena mysticetus) as indicated by stable isotope ratios

      Lee, Sang Heon; Schell, Donald; Finney, Bruce; Weingartner, Thomas (2000-12)
      The feeding habitats of the Western Arctic bowhead whales (Balaena mysticetus) during summer are generally known, but the precise amounts of food consumed from the eastern Beaufort Sea (EBS) are not known. [Alpha]13C and [alpha]15N ratios in whale tissues were used to estimate the amounts of food required from EBS. The feeding strategies of adults and subadults were also compared. For all whales, the [alpha]13C values in muscle sampled in fall were not significantly different from those in the muscle sampled in spring, indicating most food of adults and subadults comes from the Bering/Chukchi seas. The ¹³C data from baleen showed, however, that EBS may be a significant feeding area for subadults. [alpha]15N values are significantly different between fall and spring muscle in subadults, suggesting a shift to different prey and/or nutritional stress during winter followed by feeding in EBS in summer.
    • Use of family history to improve colorectal cancer screening outreach among Alaska Native people

      Redwood, Diana; Lopez, Ellen; Johnson, Rhonda; Skewes, Monica; Garcia, Gabriel (2013-12)
      Colorectal cancer (CRC) incidence and mortality among Alaska Native people are the highest of any ethnic or racial group in the United States. First-degree relatives (FDRs), which include parents, siblings, and children of CRC patients, are at increased risk. There is a paucity of data on predictors of screening adherence among Alaska Native FDRs, and the extent to which screening outreach is occurring within the Alaska Tribal Health System (ATHS) for FDRs. There is also a lack of data available on barriers and facilitators to increasing screening outreach efforts in this population. This study assessed the prevalence of CRC screening outreach to FDRs at Alaska tribal health organizations (THOS), use of family history information, barriers to CRC screening, and potential tools to improve CRC screening throughout the Alaska Tribal Health System (ATHS). The study also included a process evaluation of the Alaska Native CRC Family Outreach Program (2000-2012) based in Anchorage, Alaska. The process evaluation investigated the program's formation, evolution, and successes and challenges through a series of key informant interviews with program stakeholders. Lastly, an outcome evaluation was conducted of the Alaska Native CRC Family Outreach Program to assess predictors of screening adherence and results of screening among Alaska Native FDR program participants. The study found that CRC screening outreach was common in the ATHS, but significant barriers still exist. These barriers were especially notable for outreach to FDRs, including a lack of dedicated staff and resources. Key results of the process evaluation of the Alaska Native CRC Family Outreach Program included an incremental approach that led to a unique outreach program and revealed the need for dedicated staff to provide culturally competent patient navigation. Challenges identified included differing FDR outreach responses, health system data access and coordination, and relying on unstable grant funding for program sustainability. The outcome evaluation of the Alaska Native CRC Family Outreach Program found despite increasing programmatic outreach and FDR screening rates, a large proportion of Alaska Native FDRs were still due for screening. This was especially true among rural-dwelling and older FDRs. This study found that overall, CRC screening and awareness are increasing among the Alaska Native population, including among FDRs. However, many Alaska Native FDRs remain unscreened. There is a critical need for more research into FDR barriers and facilitators to CRC screening, as well as how the ATHS can more systematically promote screening among this increased-risk population and reduce morbidity and mortality due to this preventable disease.
    • The use of social network analysis by school librarians to evaluate and improve collaborative networks in their secondary schools: a pilot study

      Rinio, Deborah; Jacobsen, Gary; Adams, Barbara; Stanley, Sarah; Richey, Jean; Gerlich, Bella (2018-05)
      Social capital, in the form of relationships among teachers, results in sharing information and resources, which leads to improved student academic achievement. As schools continue to seek out ways to improve performance, social capital is often overlooked in favor of development of human capital in the form of professional development and training. Schools that have implemented collaborative groups have the potential to increase social capital, but often fail to structure the groups intentionally or evaluate their outcomes. School librarians in secondary schools often face challenges when it comes to collaboration. The job of a school librarian is inherently collaborative. To effectively serve the school's population, school librarians must understand the needs of their community. To teach information literacy skills, they must have access to students, typically via classroom teachers. Not surprisingly, collaboration between teachers and librarians is a major focus of both professional and research literature, yet librarians report it is one of their biggest challenges. Librarians are urged to start small, work with the teachers who are willing, and hope that others in the school will see the value of collaboration; in other words, build it and they will come. This research sought to determine if school librarians could use social network analysis as an evaluative and strategic planning tool. This study used a mixed-methods approach in a three-phase process to collect social network survey data in two secondary schools, develop the Social Network Analysis for School Librarians (SNASL) Process, and pilot test the process with the school librarians in the pilot schools using participatory analysis. Analysis revealed that the SNASL Process has the potential to enable school librarians to evaluate and improve upon the collaborative network of their school by identifying individuals in specific role positions and producing generative insight regarding the structure of the school network.
    • Use of synthetic aperture radar in estimation of wave climate for coastal engineering design

      Blackstone, Jill Ellen (1995)
      Development of Alaska's maritime resources requires design of efficient, reliable, safe facilities by coastal engineers who have a thorough knowledge of site specific wave climate: wave height, length, period, direction, and storm duration. Unfortunately, lack of wave information and validated hindcast models along the Alaskan coast often results in costly overdesigned facilities or underdesigned coastal structures which have a high risk of performance failure. To expand the nearshore wave climate availability, use of spaceborne synthetic aperture radar (SAR) data to estimate wave parameters was evaluated. SAR data were examined in raw and filtered forms, and the extracted wave climate compared to field measured data at three sites. Based on this comparison, the applications and limitations of SAR estimated parameters were established and incorporation of the information into current design practice was addressed. SAR based spectra were dominated by low frequency spectral peaks, likely due to random noise associated with SAR images, as these peaks were not present in the field measured spectra. Due to discrepancies between SAR and measured spectra, wave height, and storm duration could not be determined. Although error ranged from 12.5% to over 100% for SAR estimated wave lengths, the fact that wave lengths, although inaccurate, could be determined from SAR is promising. SAR based wave direction compared favorably to theoretical propagation directions which affirms the potential of wave parameter extraction from SAR data. However, directional field data were not available for comparison. Due to the current errors associated with SAR based wave estimations, SAR estimated wave climate cannot be incorporated into coastal design practice at this time. Research results suggest SAR data still hold great potential for estimating wave parameters. Examination of SAR based wave climate in an extensively monitored, open ocean setting would be beneficial, and the influence of environmental factors on SAR imaging of waves warrants additional investigation. Furthermore, development of a tandem SAR platform with temporal resolution on the order of seconds would be useful for wave period estimation and interferometric wave height determination. After this background research has been accomplished, another evaluation of SAR based nearshore wave climate would be worthwhile.
    • Use of Tlingit art and identity by non-Tlingit people in Sitka, Alaska

      Kreiss-Tomkins, David; Anahita, Sine; Leonard, Beth; Mehner, Da-ka-xeen (2014-05)
      Tlingit culture, as with many Indigenous cultures that exist under colonial rule, is often described as being in danger of disappearing. Despite this, the appropriation of and subsequent use of cultural practices by non-Tlingit people, and especially white people, is a continuation of the process of colonization when it is enacted in a manner that is not critical of current and historical racism, capitalist pressures and colonial violence. This project addresses the topic through recorded conversations with seven Tlingit women in Sitka, Alaska in an attempt to place Tlingit cultural production and use in the broader contexts of Indigenous cultural sovereignty and resistance to US imperial power. While various types and extremes of cultural appropriation are examined and compared to theory examining privilege and oppression, this project does not delineate general rules for appropriate and inappropriate use of culture.
    • User interface and function library for ground robot navigation

      Smith, Micah; Lawlor, Orion; Genetti, Jon; Chappell, Glenn (2017-05)
      A web application user interface and function library were developed to enable a user to program a ground robot to navigate autonomously. The user interface includes modules for generating a grid of obstacles from a map image, setting waypoints for a path through the map, and programming a robot in a code editor to navigate autonomously. The algorithm used for navigation is an A* algorithm modified with obstacle padding to accommodate the width of the robot and path smoothing to simplify the paths. The user interface and functions were designed to be simple so that users without technical backgrounds can use them, and by doing so they can engage in the development process of human-centered robots. The navigation functions were successful in finding paths in test configurations, and the performance of the algorithms was fast enough for user interactivity up to a certain limit of grid cell sizes.
    • Using equine-facilitated psychotherapy to treat eating disorders

      Donofry, Susana; Cook, Christine; Healy, Joanne; Harrison, Lynn (2014)
      Eating disorders are pervasive mental disorders that can be accompanied by significant psychological symptoms and comorbidities, such as: suicide, anxiety, and depression. The binging and purging behaviors that often accompany eating disorders can result in significant medical issues such as dehydration, heart arrhythmias, seizures, kidney problems, and death. Eating disorders affect males and females alike, as well as adults and children, and are most predominant among Western cultures. Eating disorders often involve binge eating episodes, periods of starvation, and purging behaviors such as self-induced vomiting, laxative use, and excessive exercise. Treatment options for decreasing the symptoms of eating disorders include: pharmacological interventions, psychological interventions, exercise interventions, and equine facilitated psychotherapy (utilizes psychological interventions in combination with equine activities). This literature review provides a basis for a PowerPoint presentation that states the benefits of adding equine-facilitated psychotherapy to the list of top research priorities, as well as describes the benefits and limitations of this newer form of therapy.
    • Using experimental design and response surface methodology to model induced fracture geometry in Shublik shale

      Poludasu, Venkatasai Sri Chand; Ahmadi, Mohabbat; Hanks, Catherine; Awoleke, Obadare (2014-12)
      The Triassic Shublik Formation of the Alaska North Slope is a world-class resource rock and has been identified as the major source of many of the conventional hydrocarbon accumulations on the North Slope, including Prudhoe Bay. Recent interest in the Shublik as a potential shale resource play has highlighted the need for robust hydraulic fracture modeling and simulation of the interval, but little geologic information is available because of the remote nature of the region and the complex character of the Shublik. In this study, a methodology was developed for identifying the critical variables needed for accurate planning of a hydraulic fracturing treatment in a play like the Shublik where much of the geology remains unconstrained. These identified critical variables can be used to develop a proxy model that can be used in lieu of a numerical simulator. This study was conducted in two stages. The first stage used 2-level fractional factorial design to identify the statistical significance of the input variables on the simulated fracture geometry. This stage was conducted in three phases, each phase incorporating progressively more complex assumptions about geology. Using the three most significant variables identified from first stage, the second stage of this study applies Box-Behnken experimental design and response surface methodology for quantifying functional relationships between input variables and the predicted fracture geometry. A pseudo 3D numerical simulator (Fracpro PT) and MATLAB were used to develop proxy models. These proxy models, typically a polynomial equation, are an easier alternative to Fracpro PT and can predict the fracture geometry with very less computational time. The use of experimental design drastically reduces the number of simulations required to evaluate large number of variables. With only 137 simulations, 26 variables were ranked based on their statistical significance and a non-linear proxy model was developed. Predicted values of the fracture geometry obtained using the proxy models were in good agreement with the simulated values of the fracture geometry (R2 value of 99.39% for fracture length, R2 value of 99.54% for fracture height and R2 value of 98.17% for fracture width).
    • Using fishers' knowledge to explore spatial fishing patterns, perceptions of regulations, and environmental change in Alaska

      Chan, Maggie; Beaudreau, Anne; Criddle, Keith; Loring, Philip; Vander Naald, Brian (2018-08)
      In this dissertation, an interdisciplinary approach was used to examine fisher knowledge from recreational charter and subsistence fishers targeting Pacific halibut (Hippoglossus stenolepis) in Alaska. The first chapter identified biological, regulatory, social, and economic drivers of spatial fishing patterns by charter operators in two communities in Alaska. In Homer, the most frequently cited reasons for changes in the location and/or extent of fishing were changes in trip type and the price of fuel, while in Sitka, the most frequently cited reasons for spatial shifts were changes to Pacific halibut regulations and gaining experience or exploring new locations. The second chapter examined perceptions of charter operators to traditional and novel recreational fishery management tools. Results highlighted that controls on individual harvest can be perceived to have unintended consequences for charter businesses, such as effects on profitability and distance traveled. The third chapter explored variability in local ecological knowledge (LEK) of fish abundance and body size trends among charter operators and subsistence harvesters. Results suggested that peoples' perceptions of fish abundance and body size can be affected by attributes of their fishing experience and highlighted the importance of including people with different types of experience in the environment when using LEK to document environmental changes. Together, these chapters contribute to an improved understanding of the human dimensions of small-scale fisheries in Alaska, including perceptions of fishers regarding the management system and shifts in fishing behavior in response to environmental, socioeconomic, and regulatory change. Additionally, this project documented and evaluated variation in local ecological knowledge to contribute new information on data-limited marine fish species in Alaska.
    • Using Geophysical Constraints To Determine Groundwater Travel Times, Seafloor Arrival Locations, And Saltwater Concentrations For Transition Zone Depths At Underground Nuclear Detonations On Amchitka Island

      Wagner, Anna M.; Barnes, David (2007)
      There is a great amount of radioactive material in the subsurface of Amchitka Island as a result from underground nuclear testing performed between 1965 and 1971. It is unknown how long it will take for the radionuclides to travel to the seafloor and the marine environment or where possible seepage zones will occur. The contaminant transport is greatly affected by the location of the transition zone (TZ) and the effective porosity, which were both determined by magnetotellurics (MT) in 2004. The hypothesis of this study was as follows: the groundwater travel times and seafloor arrival locations, can be estimated through groundwater modeling, with the location of the transition zone being estimated by magnetotellurics. An additional hypothesis is as follows: saltwater concentration for a TZ and the general subsurface characteristics can be quantified with groundwater modeling, using geophysical constraints in combination with saltwater and hydraulic head measurements. The groundwater travel times were estimated with groundwater modeling using the transition zone location as determined by MT. Shortest groundwater travel times are 1,200 and 2,100 years, at Long Shot and Cannikin respectively. At Long Shot, a decreased groundwater travel time of up to 55% could be seen when an enhanced hydraulic conductivity was included at the location of an assumed andesite sill layer. The seafloor arrival locations can be up to 1,000 and 2,100 m offshore at Long Shot and Cannikin respectively but will most likely occur closer to shore. This study was also successful at establishing the general characteristics of the subsurface by using geophysical constraints in combination with saltwater and hydraulic head measurements. The subsurface at Long Shot is isotropic or has mild anisotropy ratio of 1:2, which confirms the study by Fenske (1972). As represented in this study, this method has been shown to be valuable in determining the saltwater concentration of the TZ as determined by MT and can thus be used in further studies of islands and coastal areas.
    • Using GIS-based and remotely sensed data for early winter moose (Alces alces gigas) survey stratification

      Clyde, Karen J. (2005-05)
      Stratification of moose survey areas is a key step to reduce population estimation variance. In the Yukon and Alaska, use of fixed-area grids for early winter moose counts combined with the increasing availability of GIS and remotely sensed data provide the opportunity to develop standardized and repeatable habitat-based stratifications. I used univariate comparisons, stepwise regression and AIC modeling to describe moose distribution as a function of landscape level variables for an area in west central Yukon during 1998 and 1999. Results quantified early winter habitat use of upland shrub habitats and support previous observations for early winter moose habitat use in Alaska, Minnesota and Montana. Number of patches, in association with areas of alpine and shrubs, were found to be highly influential for survey blocks where moose are expected to be present and in high numbers. Overall, model performance based on relative abundance of moose was less predictive than for blocks where moose were present or absent. Spatial resolution of GIS and remotely sensed data used in this study (25 m grid cells) provided sufficient spatial detail to generate correlations between moose presence and habitat for a first level stratification.
    • Using histomorphometric traits of bone microarchitecture in the determination of biological affinity

      Goodman, E. Augustus (2002-08)
      This research began to establish alternate possible means for determining the biological affinity for fragmented skeletal remains between geographically disparate populations, specifically American-Caucasians and Southeast Asians. The goal is to determine the feasibility of developing a method that may be used in the field to differentiate the remains of U.S. servicemen from people of Southeast Asia. This technique is based upon differences in bone histomorphometric variables. The variables used in this research are the osteon area (On. Ar), Haversian canal area (H. Ar), and osteon population density (OPD). The conclusions reached in this research suggest that differences exist on the population level among these two populations. Histomorphometric differences exist on the population level among these two populations. Histomorphometric differences occur within mean Haversian canal area measurements and osteon population densities. However, it is not possible to discern which variables are principally accountable for the differences.
    • Using infrasound to characterize volcanic emissions at Tolbachik, Karymsky, and Sakurajima volcanoes

      Albert, Sarah; Fee, David; Tape, Carl; Szuberla, Curt (2015-08)
      The work presented herein includes one main body of research on infrasound from Tolbachik Volcano and suggestions for future work on eruption dynamics using infrasound from other volcanoes. We use both regional and local infrasound data to track the dynamics of the 2012-2013 eruption of Tolbachik Volcano, Kamchatka, Russia. Analysis of regional data recorded at the IMS array IS44 in southern Kamchatka, ~384 km from the vent, focuses on the eruption onset in November 2012, while analysis of local data recorded 100-950 m from the vent focuses on activity in February and August 2013. Signals recorded from Tolbachik suggest an increase in eruptive intensity occurred from November 28-29, 2012. Local infrasound data are characterized primarily by repeated, transient explosion signals indicative of gas slug bursts. Three methods are employed to pick slug burst events in February and August, with all methods proving to be effective. The nature of slug bursts makes a monopole acoustic source model particularly fitting, permitting volume outux and slug radius calculations for individual events. Volume outuxes and slug radii distributions provide three possible explanations for the eruption style of Tolbachik Volcano from mid-February to late August. Cumulative outux for slug bursts (i.e. mass of emissions from individual bursts) derived by infrasound for both February and August range from <100 to 3000 kg. These values are greater than infrasound-derived emissions calculated at Pacaya Volcano, but less than those calculated at Mt. Erebus Volcano. From this, we determine slug bursts at Tolbachik Volcano in February and August were larger on average than those at Pacaya Volcano in 2010, but smaller on average than those at Mt. Erebus in 2008. Suggestions for future work are also given after analysis of acoustic waveforms from local infrasound data collected at Karymsky and Sakurajima Volcanoes. Activity at both of these volcanoes ranges from short-duration ash-rich explosions to longer-duration ash-rich explosions. A multiparameter dataset collected at Karymsky Volcano in August 2011 includes infrasound data, gas and ash data, and thermal imagery from eruptive events. Content of gas vs. ash, general plume characteristics, plume altitude above the vent, plume temperature, and SO₂ emission rates are correlated with acoustic waveform families identifed at each volcano using a cross correlation method. This preliminary analysis shows promise for correlating acoustic waveforms with eruptive activity and can likely be improved with future work.
    • Using local knowledge to inform commercial fisheries science and management in Poland and Alaska

      Figus, Elizabeth Carroll; Criddle, Keith; Carothers, Courtney; Beaudreau, Anne; Kuzebski, Emil (2018-05)
      Science and decision making in commercial fisheries management take place in the context of uncertainty. This research demonstrates ways that local knowledge held by fishermen can be used to mitigate that uncertainty. This dissertation documents local knowledge of fishermen in Poland and Alaska, and contributes to the development of methods for utilizing that local knowledge in commercial fisheries management. Specific case study examples were developed through exploratory interviews with fishermen in the two study regions. Interviews were conducted with Baltic cod (Gadus morhua) fishermen in Poland and Pacific halibut (Hippoglossus stenolepis) fishermen in Alaska. Qualitative and quantitative methods were used to analyze local knowledge about ecosystems, as well as preferences held by fishermen about regulations. Cultural consensus analysis was used to quantify agreement among fishermen in Poland about the abundance and condition of cod, and generalized additive modeling was used to show how fishermen and scientists attributed different causes to similar observed phenomena. Multiple factor analysis and logistic regression were used to demonstrate how fishing characteristics influence encounters with incidental catch in the commercial fishery for halibut in Southeast Alaska. Finally, an analytic hierarchy process model was used to shed light on preferences halibut fishermen have about data collection methods on their vessels. All findings show how the inclusion of fishermen's local knowledge in fisheries management need not be limited to informal conversations or public testimony at meetings in order to be meaningfully interpretable by managers.
    • Using Multicultural Literature To Promote Cultural Awareness And Deepen Understanding Of Your Own: A Yup'ik Teacher-Researcher's Journey

      Sundown, Nuraraq Joanne T.; Parker-Webster, Joan; Siekmann, Sabine (2010)
      The purpose of this research is to see if using multicultural literature potentially enhances a student's own respect of his/her culture and language. Through the use of a multicultural thematic unit and multicultural literature, students potentially gain awareness and respect for diverse populations. This research hopes to see this diverse awareness and respect reflected on the students' own culture and language. The research conducted was a qualitative research using participants enrolled in the Scammon Bay School for the school year 2008-2009. The participants were nine second grade students. The research methods outlined several techniques such as interviews, observations, and student artifacts, namely the Make Connections Organizer. Data collection began December 2008 and ended May 2009. The goal is to find out how students responded and/or connected to the multicultural literature as it may relate to their own culture and language.
    • Using multispectral aerial imagery and GIS-based approaches to quantify juvenile salmon rearing habitat in the Kulukak River, Alaska

      Woll, Christine; Sutton, Trent; Prakash, Anupma; McPhee, Megan (2012-05)
      Monitoring the quality and quantity of freshwater rearing habitat for Pacific salmon Oncorhynchus spp. is essential for maintaining stocks of these species. Because field-based habitat monitoring in remote areas can be expensive, time-consuming, and/or subjective, new methods are desired. The objectives of this study were (1) to develop methods for using multispectral aerial imagery to classify juvenile rearing habitat and determine the accuracy of these methods and (2) to use these methods to quantify and map juvenile salmon habitat characteristics in two study areas in the Kulukak River, Alaska. I demonstrated that a decision-based fusion approach using images acquired in the visible, near-infrared, and thermal-infrared regions classified habitat classes important for juvenile salmon with accuracies of 82.5% and 67.5% in the respective study areas. In addition, I quantified and mapped habitat variables often used in juvenile salmon studies on several scales and created habitat-suitability maps for coho salmon O. kisutch, demonstrating that both my study areas differed in habitat quantity and quality and are most likely low-quality rearing areas. This study demonstrates that airborne images can be used to determine the quality and quantity of juvenile Pacific salmon rearing habitat in small streams and thus decision support in fisheries management.
    • Using otolith strontium isotopes to elucidate population structure and movements of Bering cisco (Coregonus laurettae)

      Padilla, Andrew John; Wooller, Matthew; Adkison, Milo; López, Andrés (2015-05)
      Methods for stock discrimination and tracking the movements and distribution of fishes have often involved expensive field logistics, a problem compounded in remote regions such as Alaska. An alternative approach is to use the chemical signatures preserved in otoliths, or ear bones, of teleost fishes to discriminate stocks or to track the movement history of fish. Currently, a commercial fishery targeting the anadromous Bering cisco Coregonus laurettae is occurring in the Yukon River, Alaska. There are only three known Bering cisco spawning rivers worldwide, the Yukon, South Fork Kuskokwim (Kuskokwim), and Susitna rivers. Managers and researchers believed that two of the three spawning-river populations (Yukon and Kuskokwim rivers) were being harvested in the fishery, due to major coastal currents linking two of the spawning rivers' deltas. To determine the likelihood of a mixed-stock fishery, in Chapter 1, I used the strontium isotope signature (⁸⁷Sr/⁸⁶Sr) preserved in the freshwater portion of otoliths to establish a baseline for the three natal rivers. The baseline data set was composed of otoliths from spawning adult Bering cisco of known origin (n=82). Subsequently, the baseline was used to classify commercially harvested Bering cisco (n=139) and determine the stock composition of the fishery. Greater than 97% of the commercial samples were classified as Yukon River origin. However, 0.7%, and 1.4% of the commercial samples were classified as originating from Kuskokwim and Susitna rivers, respectively. In Chapter 2, I used the baseline data to classify Bering cisco from three coastal rearing areas (Alaska Arctic coast, n=49; Y-K Delta, n=70; and the Alaska Peninsula, n=8). More than 96% of the coastal rearing Bering cisco had ⁸⁷Sr/⁸⁶Sr signatures consistent with a Yukon River origin. These data demonstrate the wide-spread coastal distribution of Bering cisco, with some travelling >4,900 km between coastal rearing and spawning habitats. This approach illustrates that ⁸⁷Sr/⁸⁶Sr can determine the natal river of Bering cisco. Subsequently, this method can be used for stock discrimination and elucidating migration patterns for unknown origin Bering cisco.
    • Using rate transient analysis and bayesian algorithms for reservoir characterization in hydraulically fractured horizontal gas wells during linear flow

      Yuhun, Pirayu; Awoleke, Obadare; Ahmadi, Mohabbat; Hanks, Catherine (2019-05)
      Multi-stage hydraulically fractured horizontal wells (MFHWs) are currently a popular method of developing shale gas and oil reservoirs. The performance of MFHWs can be analyzed by an approach called Rate transient analysis (RTA). However, the predicted outcomes are often inaccurate and provide non-unique results. Therefore, the main objective of this thesis is to couple Bayesian Algorithms with a current production analysis method, that is, rate transient analysis, to generate probabilistic credible interval ranges for key reservoir and completion variables. To show the legitimacy of the RTA-Bayesian method, synthetic production data from a multistage hydraulically fractured horizontal completion in a reservoir modeled after Marcellus shale reservoir was generated using a reservoir (CMG) model. The synthetic production data was analyzed using a combination of rate transient analysis with Bayesian techniques. Firstly, the traditional log-log plot was produced to identify the linear flow production regime, which is usually the dominant regime in shale reservoirs. Using the linear flow production data and traditional rate transient analysis equations, Bayesian inversion was carried out using likelihood-based and likelihood-free Bayesian methods. The rjags and EasyABC packages in statistical software R were used for the likelihood-based and likelihood-free inversion respectively. Model priors were based (1) on information available about the Marcellus shale from technical literature and (2) hydraulic fracture design parameters. Posterior distributions and prediction intervals were developed for the fracture length, matrix permeability, and skin factor. These predicted credible intervals were then compared with actual synthetic reservoir and hydraulic fracture data. The methodology was also repeated for an actual case in the Barnett shale for a validation. The most substantial finding was that for all the investigated cases, including complicated scenarios (such as finite fracture conductivity, fracturing fluid flowback, heterogeneity of fracture length, and pressure-dependent reservoir), the combined RTA-Bayesian model provided a reasonable prediction interval that encompassed the actual/observed values of the reservoir/hydraulic fracture variables. The R-squared value of predicted values over true values was more than 0.5 in all cases. For the base case in this study, the choice of the prior distribution did not affect the posterior distribution/prediction interval in a significant manner in as much as the prior distribution was partially informative. However, the use of noninformative priors resulted in a loss of precision. Also, a comparison of the Approximate Bayesian Computation (ABC) and the traditional Bayesian algorithms showed that the ABC algorithm reduced computational time with minimal loss of accuracy by at least an order of magnitude by bypassing the complicated step of having to compute the likelihood function. In addition, the production time, number of iterations and tolerance of fitting had a minimal impact on the posterior distribution after an optimum point--which was at least one-year production, 10,000 iterations and 0.001 respectively. In summary, the RTA-Bayesian production analysis method implemented in relatively easy computational platforms, like R and Excel, provided good characterization of all key variables such as matrix permeability, fracture length and skin when compared to results obtained from analytical methods. This probabilistic characterization has the potential to enable better understanding of well performance, improved identification of optimization opportunities and ultimately improved ultimate recovery from shale gas resources.