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Floodplain is an important location for the economic and social development of society throughout history, although it afflicted by different disasters like floods and bank erosion from time to time. Population dynamics and distribution trends have important effects on the landscape and society. Population dynamics in floodplains influenced mostly by the flood events and related human activities to protect themselves and the properties. Thus, floodplain population dynamics is vital to understand human-nature relationships, disaster risk assessment, flood forecasting and flood damage costs in the floodplains. Economic losses and fatalities due to flood events increase with increased flood frequency and flood magnitude. Extreme hydrological changes are responsible for such changes in the flood events. Population growth, urbanization and developmental activities worsened the situation further in the floodplain areas. Learning effect, i.e. flood memory is noticeable after the flood which diminishes with time, however, levee, which is a popular flood protection measure, causes further reduction of learning effect. Researchers suggest that levees create a false sense of safety and can influence the mobilization of floodplain population. Several pieces of research indicate that along with flood events and intervention measures, inundation depth, durations, flood type (coastal/ riverine), economic, technological and political characteristics of the societies influence flood memory, hence, influence floodplain population dynamics. However, long term floodplain population dynamics and how it is related to different flood-related, i.e. hydrological and sociological variables are yet to be confirmed. Flood is one of the major natural disasters in the United States. About 10% of the population lives in the 100-year and 500-year floodplain of the United States. This study carried out to investigate the long-term trend of floodplain population dynamics in the USA and how the dynamics changes from country to state to county level considering Arkansas State and Sebastian County to observe the difference. Also, the relationships of floodplain population dynamics with hydrological and sociological variables such as flood events, damage, intervention measures and poverty assessed in the national, state and county level. Then the dynamics of the national level, the state (Arkansas) level and the county (Sebastian) level were compared to identify changes in dynamics from macro to micro-scale. Floodplain population dynamics evaluated in terms of population growth rate and the ratio of floodplain population to the total population from 1790 – 2010. The median centroids of the population growth rate from 1790 – 2010 were estimated to observe the changes in the central tendency of the population growth rate in the total area and in the floodplain overtime to locate the typical place of floodplain population growth. High-resolution raster image (1 km x 1 km) of historical population data and a high-resolution raster image (250 m x 250 m) of floodplain data were analysed using ArcGIS to evaluate floodplain population dynamics. Historical data regarding flood events, damage, structural and non- structural flood intervention measures and poverty from available databases were extracted, processed and analysed to establish the relationship among population dynamics, hydrological and social variables. Finally, the population dynamics of the three levels were compared statistically and discussed for changes. It is found that the central tendency of the total population growth rate and floodplain population growth rate of the USA shifts from east to west direction. The central tendency of the overall population growth rate located near the lower Mississippi river basin in the 1800s. It is consistent near the geographical centroid of the USA in Kansas since 1900. For the floodplain population, the central tendency of the growth rate stayed consistent in Arkansas from 1910 – 2010, i.e. in the lower Mississippi river basin. This location indicates the floodplains in Arkansas was preferable for floodplain population settlement for many decades. Change in floodplain population proportion of the whole country USA from 1790 – 2010 shows that the proportion of floodplain population is more than 80% during the initial years of settlement. Then it reduced to less than 40% over time. At the state level – Arkansas, the proportion of floodplain population is also more than 80% during initial settlement and reduced to less than 60% over time for counties with high percentage floodplain area. Flood events, structural and non-structural protection measures influenced floodplain population dynamics over time and learning effect, i.e. social memory of flood found was seven years. At the county level- Sebastian county, Arkansas, the proportion of floodplain population varies significantly with a variance of 0.04 and a standard deviation of 0.19. The ratio of floodplain population in Sebastian was 29% in 1820, which increased and decreased over the years and about 70% in 2010. In addition to flood events, different intervention measures, the floodplain population dynamics in the Sebastian county are influenced by the social, economic and political phenomenon, examining which is out of the scope of this study. The learning effect of flood seems to be eight years in the case of Sebastian county. The population dynamics influenced by a different social, geographical, economic, political and hydrological phenomenon which makes it a complicated system to comprehend within the present scope of the study. The result shows that the floodplain population dynamics can vary for different geographical scale. Therefore, the geographic extent should also need to consider while using population dynamics in flood disaster management and mitigation strategy development, policy formulation and implementation. / Flodslätter är viktiga platser för samhällets ekonomiska samt sociala utveckling och har varit det sedan är lång tid tillbaka, även om de från och till har drabbats av olika katastrofer såsom översvämning och erosion. Översvämning är en av de största naturliga katastrofer som sker i USA. Ungefär 10 % av befolkningen bor i 100- och 500-års flodslätter som emellertid förändras på grund av olika anledningar, inklusive översvämningar. I denna studie undersöks den tillfälliga relationen mellan översvämning, relaterad skada, olika ingripande åtgärder och fattigdomsnivå med en befolkningsdynamik i flodslättsområden. Vidare sker denna undersökning i tre olika nivåer – nationellt: USA som ett helt land, stats-nivå: Arkansas och län: Sebastian County, Arkansas där de olika dynamikerna i de tre nivåerna jämförs. På den nationella nivån utvärderades befolkningsdynamiken med avseende på flodslätten till den totala populationen och befolkningstillväxt. Resultatet visar att befolkningsdynamiken förändras beroende på om den betraktas ur ett nationellt, statligt eller läns perspektiv. Ur ett nationellt perspektiv flyttar flodslättsbefolkningar till olika områden med tiden. Ur ett statligt perspektiv är flodslättsbefolkningar känsliga mot översvämningar, skada och olika ingripande åtgärder. På länsnivå, utöver översvämningsrelaterade variabler, är flodslättsbefolkningar känsliga mot andra socio-ekonomiska faktorer som inte behöver vara relaterade till översvämningar. Resultatet indikerar således att översvämningar inte alltid behöver vara den faktorn som styr befolkningsdynamiken i flodslättsområden på den lokala nivån samt beslutet att flytta till en flodslätt påverkas av olika socio- ekonomiska faktorer, inklusive översvämning. På den nationella nivån kan däremot både påverkan av översvämningar och relaterade variabler på befolkningsdynamiken i flodslättsområden observeras.

Estimation of natural mortality within statistical catch-at-age models has been relatively unsuccessful and is uncommon within stock assessments. The models I created estimated population-dynamics parameters, including natural mortality, through Metropolis-Hastings algorithms from Gulf of Mexico red-snapper Lutjanus campechanus data. I investigated the influences of assumptions regarding model configuration of natural mortality and selectivity-at-age parameters by comparing multiple models. The results of this study are preliminary due to parameter estimates being bounded by uniform priors and thus a potential lack of convergence to the posterior distribution. Estimation of a natural-mortality parameter at age 0 or a Lorenzen natural-mortality parameter could be confounded with selectivity-at-age-1 parameters for bycatch from the shrimp fisheries. The Lorenzen natural-mortality curve was calculated by dividing the parameter by red snapper length at age. An age-1 natural-mortality parameter might not be estimable with the currently available data. Values of the natural-mortality parameter for ages 2 and older appear to be slightly less influenced by assumptions regarding selectivity-at-age parameters. We conducted a simulation study to determine the accuracy and precision of natural-mortality estimation assuming the selectivity-at-age-1 parameter for bycatch from the shrimp fisheries equaled 1.0 and a Lorenzen natural-mortality curve. The simulation study indicated that initial abundance-at-age parameters may be inestimable within the current model and may influence other parameter estimates. The preliminary simulation results showed that the Lorenzen natural-mortality parameter was consistently slightly underestimated and apical-fishing-mortality parameters were considerably underestimated. The estimation of natural mortality within a statistical catch-at-age model for Gulf of Mexico red snapper has many caveats and requires additional investigation. / Master of Science

Understanding the effects of large-scale disturbances and associated management actions on imperiled species can increase conservation value of future management. Piping plovers (Charadrius melodus) are federally threatened and endangered, disturbance-dependent shorebirds, nesting on broad, sparsely vegetated beaches, sandbars, and lakeshores. In October 2012, Hurricane Sandy storm surges cleared vegetation and opened old and new inlets through Fire Island and Westhampton Island, New York, creating plover habitat. Storm effects prompted an island-wide stabilization project, and certain sections of Fire Island were designed to create and/or improve plover habitat (hereafter, restoration areas) to mitigate possible habitat loss or degradation. Many plover populations range-wide appear to be habitat-limited, and we anticipated positive population growth following habitat creation. To help predict what might happen to the plover population following Hurricane Sandy, we evaluated the effects of habitat-creating events at several other locations in the range, evaluating the hypothesis that plover population sizes are habitat limited. We estimated the amount of habitat available before and after four significant storm and flooding events by classifying pre- and post-disturbance aerial imagery and evaluated the population changes that occurred after disturbance-related habitat alterations. Following these habitat creating events, nesting habitat increased 27%–950%, and, subsequently, these plover populations increased overall 72%–622% (increase of 8–217 pairs in 3 to 8 years after the disturbance, average 12–116% increase annually). The demographic changes likely were driven by some combination of productivity and immigration occurring simultaneously with regional increases. We then evaluated population and suitable habitat change on Fire Island and Westhampton Island following Hurricane Sandy. We developed an integrated population model to determine the primary contributors to population and assessed the effect of restoration areas on demographic processes during 2013–2018. We also recorded individual locations of adults and pre-fledge chicks to evaluate effects of post-Hurricane Sandy landscape features on resource selection of adults and chicks, and behavior and survival of plover broods. We evaluated whether breeding stage (pre-breeding, nesting, brooding, post-breeding), simple breeding stage (breeding, not-breeding), or instantaneous behavior class (parental, non-parental) best explained habitat selection during the 5-month plover breeding season. We also evaluated the effects of post-Hurricane Sandy landscape features on resource selection, behavior, and survival of plover broods during 2013–2019. We observed positive population growth in three of five years and overall growth through the study (λ ̅=1.12). Immigration and reproductive output were correlated with population growth (r = 0.93 and 0.74, respectively). Compared to the rest of the study area, restoration areas had higher chick survival but lower nest survival and breeding fidelity, and population growth (λ ̅=1.09) in restoration areas was similar. For adult plovers, behavior class best explained habitat selection. Compared to non-parental plovers, plovers engaged in parental behavior (incubating, brooding, and accompanying chicks, hereafter 'parental') selected areas closer to bay intertidal habitats and with more dry sand. Non-parental plovers avoided areas with more dry sand and did not select for or against bay intertidal habitats. Additionally, non-parental plovers avoided development more than parental plovers and avoided areas of lower elevation more than parental plovers. In each year, there was more suitable habitat for parental plovers than non-parental plovers. Plover broods selected for flatter sites with less vegetation but selected for sites closer to development as time since Hurricane Sandy increased. Chick foraging rates were highest in moist substrates and were negatively influenced by nesting plover density. Chick survival was negatively influenced by nesting plover density and was greater for earlier hatched broods. Further, chick survival was higher following an outbreak of sarcoptic mange in the local red fox (Vulpes vulpes) population. If human interventions were reduced or modified in such a way as to create, maintain, and improve habitat, plover populations likely would reach higher numbers, and the potential for achieving recovery goals would be increased. Future restoration areas projects could use Great Gun as a model, although design criteria could be improved to increase access to moist, flat, low energy foraging sites. Efforts to increase immigration of novel breeding adults into the system, primarily by habitat creation or maintenance, are likely to have the greatest local effect on population growth but may not improve regional population persistence if habitat creation is only local. Management to improve reproductive output is likely to have a positive effect on population growth if there is suitable habitat to support recruits and will improve regional population persistence by producing emigrants. When improving or creating plover habitat, managers should consider habitat needs both for plovers of all life stages. Habitat management should focus on maintaining vegetation-free sand and access to low-elevation foraging habitat. Allowing hurricanes such as Hurricane Sandy to alter the landscape naturally will create these landscape features. / Doctor of Philosophy / Piping plovers (Charadrius melodus) are federally threatened and endangered shorebirds that nest on sandy beaches, sandbars, and lakeshores. In October 2012, Hurricane Sandy created substantial habitat on Fire Island and Westhampton Island, New York, which could have acted as plover habitat. However, concerns about mainland safety from future storms prompted an island-wide project, building dunes planted with beach grass, to improve ability of Fire Island to protect the mainland. However, planted dunes had the potential to negatively affect newly created habitat, and certain sections of Fire Island were designed to create plover nesting habitat. Because of the habitat creation, we predicted that the population would increase. To illustrate that habitat creating events lead to plover population increases, we used freely available aerial imagery and identified all areas of dry and moist sand in study areas. We then used local plover monitoring data to relate habitat change to plover population change, and found that for several hurricanes and floods in the piping plover range, habitat increases led to population increase. We then evaluated population change on Fire Island and Westhampton Island, and found that the population increased 90% following Hurricane Sandy, and the increase was primarily due to new immigrant adults, and local reproductive success. The created restoration areas had similar reproductive output and population growth to the rest of the study area. To determine the areas on Fire Island and Westhampton Island that were adequate habitat for piping plover adults, we compared habitat used by plovers to what was available on the island and determined that habitat use differed between adults exhibiting parental behaviors and adults exhibiting all other behaviors. Non-parental plovers avoided dry sand. Both parental and non-parental plovers avoided development and high elevation sites. Overall, more sand was suitable for parental plovers than non-parental plovers. Because reproductive output also was influential to the population increase on Fire Island, we evaluated effects of landscape features on plover chick habitat, foraging, and survival. Plover chicks avoided vegetation, and selected flatter areas, but selected sites closer to development as time since Hurricane Sandy increased. Chicks spent more time foraging in moist substrates, and less time foraging when there were more plovers nesting in a management unit. Chick survival also was lower when more plovers were nesting in a management unit and was greater for earlier hatched broods. Further, chick survival was higher following a sharp decline in the local red fox (Vulpes vulpes) population. Overall, Hurricane Sandy was a positive force for this local plover population and local efforts to allow hurricane storm surges to modify the island in the future will improve long-term population persistence. Efforts to increase immigration of novel adults into Fire Island and Westhampton Island, primarily by habitat creation or maintenance, are likely to have the greatest local effect on positive population growth. Improving reproductive output is likely to have a positive effect on local and regional population growth, particularly by maintaining a low red fox population, if there is suitable habitat to support recruits. When improving or creating plover habitat, managers should consider habitat needs for plovers across the whole breeding season rather than just nesting. Habitat management should focus on maintaining vegetation-free sand, and access to low-elevation, flat foraging habitat. Habitat creation also may increase habitat amount and therefore local population growth.

A demographic population simulation model was developed to examine alternative fishery management strategies and their likely effects on the probability of extirpation of local eastern oyster (Crassostrea virginica) populations in the Chesapeake Bay. Management strategies include varying the minimum shell length-at-harvest, harvest rate, and rate and frequency of stocking of oyster seed with respect to varying salinities and oyster population densities. We also examined the rate of disease-mediated mortality that can be tolerated by a viable population. High density populations at low salinity sites remained viable under a 100% harvest rate and 76.6 minimum shell length-at-harvest due to increased fertilization efficiency in high densities, which increased reproduction. Low density populations at low salinity sites remained viable when harvest rate was set at 0.5 and minimum shell length-at-harvest was set at 85 mm. Neither reducing harvest rate nor minimum shell length-at-harvest produced a viable population at high salinity sites. The effects of disease-mediated mortality were too great for these management options to decrease the probability of extirpation to zero. Supplemental stocking conducted regularly reduced extirpation probabilities to zero and pulse stocking (every five to ten years) did as well, although it required a much larger number of oysters to be stocked. Decreasing disease-mediated mortality rates by 20% in high density populations and by 80% in low density populations reduced the probability of extirpation to zero, suggesting the degree of genetic improvement needed to rebuild eastern oyster populations in the Chesapeake Bay. Culture of a non-native species, such as the Suminoe oyster (Crassostrea ariakensis), could supplement harvest of the declining eastern oyster fishery in Chesapeake Bay. Because of possible ecological impacts from introducing a fertile non-native species, introduction of sterile triploid oysters has been proposed. However, recent data show that a small percentage of triploid individuals progressively revert toward diploidy, introducing the possibility Suminoe oyster might establish self-sustaining populations. To assess the risk of Suminoe oyster populations becoming established in Chesapeake Bay, a demographic population model was developed. Inputs modeled included: salinity, stocking density, reversion rate, reproductive potential, natural and harvest mortality, growth rates, and effects of various management strategies, including harvest criteria. Results showed decreased probability of a Suminoe oyster population becoming self-sustaining when oysters are grown at low salinity sites, certainty of harvest is high, minimum shell length-at-harvest is small, and stocking density is low. Results of the model suggest management strategies that will decrease the probability of a Suminoe oyster population becoming self-sustaining. Policy makers and fishery managers can use the model to predict potential outcomes of policy decisions, supporting the ability to make science-based policy decisions about the proposed introduction of triploid Suminoe oysters into the Chesapeake Bay. / Master of Science

The brown marmorated stink bug (BMSB), Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is an invasive insect from Asia that has recently become a major pest of agricultural crops and a nuisance to home and business owners in the Mid-Atlantic U.S. Since 2010, H. halys has been reported in many vineyards in Virginia, but the pest significance in this crop is unknown. Sampling was conducted in four commercial vineyards across Virginia in 2012 and 2013 to study the seasonal phenology and pest status of H. halys in vineyards. Adults moved into vineyards as early as May and laid eggs usually on the undersurface of leaves, but occasionally on the berry or the rachis. Grapevines were an early season reproductive host for H. halys. A vineyard adjacent to a sub-urban area with homes and buildings in proximity had an early season peak of H. halys as compared to vineyards adjacent to woods. However, populations declined sharply in late season due to the possible movement of bugs to more preferable host plants such as soybean and corn. In contrast, H. halys was recorded throughout the grape growing period in a vineyard that was surrounded by forests. Significantly more H. halys were recorded from border than interior section of vineyards. A degree-day model suggested that there were enough degree-days to complete a generation of H. halys in Virginia vineyards. H. halys caused direct injury to the grape berries at veraison and pre-harvest berries. Injury expression in the veraison berry can be described as an appearance of a small necrotic spot at the site of the stylets insertion. The spot gradually increased in size and the berries became deformed. H. halys is an economic pest of raspberry, causing direct injury to the berries. Sampling of stink bugs in raspberry plantings in southwestern Virginia showed that the Euschistus species were the most abundant stink bugs in 2008, 2009, 2011 and 2012. However, H. halys became the most abundant in 2013. / Master of Science in Life Sciences

Three hammerhead sharks (Sphyrna spp.) are currently managed as part of the large coastal shark complex in the United States. Including multiple species in an assessment ignores the different stock dynamics of each individual species within the complex due to different life histories. This study completed individual assessments of scalloped (S. lewini), great (S. mokarran), and smooth (S. zygaena) hammerhead sharks in the U.S. Atlantic Ocean and Gulf of Mexico. Combined data for all three species and unclassified hammerhead sharks were also used to produce a stock assessment of the hammerhead shark complex. Depletions of 83%, 96%, and 91% were estimated for scalloped, great, and smooth hammerhead sharks, respectively, between 1981 and 2005. When modeled as a single stock, the hammerhead shark complex experienced a 90% decline over the same time period. All three stocks, and the complex were overfished (below population size associated with maximum sustainable yield (MSY)), and overfishing (fishing level above that associated with MSY) occurred in 2005. We found that scalloped hammerhead shark population recovery is likely to occur within 10 years if catch remains at or below 2005 levels. Great and smooth hammerhead sharks will likely still be overfished in 30 years unless catches are reduced. It appears that the species composition could be changing in this hammerhead shark complex. The faster-growing scalloped hammerhead sharks are able to withstand fishing pressure better than great or smooth hammerhead sharks. However, it is difficult to target any single large coastal shark species while fishing; hence they are subject to similar fishing pressure. The result is a greater decline in great and smooth hammerhead sharks than experienced by scalloped hammerhead sharks. Therefore, the proportion of scalloped hammerhead sharks increased between 1981 and 2005. Species-specific stock assessments, such as those presented here, allow managers to more closely monitor populations of slower-growing species and reduce the risk of overexploitation of those species. / Master of Science

Thirty-four (6 M, 28 F) of 93 black bears (<i>Ursus americanus</i>) captured during summers 1995 and 1996 were equipped with radio-collars. The mean age of male and females captured was 2.5 (<u>n</u> = 63; 2 males not aged) and 4.4 (<u>n</u> = 28) years, respectively. The mean date of females in estrus was 24 July, and we observed one 1.5-year old female in estrus. The average age of primiparity of radio-collared females was 3.0 years; however, we documented fetuses present in a 2-year old noncollared female's reproductive tract. The average interbirth interval was 1.6 years and 95.4% of females without yearlings produced cubs. The mean litter size was 2.2 and the cub sex ratio was 1.3M:1F. Hunting, vehicle collisions, poaching, research, and euthanasia accounted for 80.5%, 5.5%, 5.5%, 5.5%, and 2.8%, respectively of the adult and juvenile male mortalities (<u>n</u> = 36). Hunting, vehicle collisions, and research each accounted for 2 of the adult and juvenile female mortalities (<u>n</u> = 6). Annual harvest rates for males in 1995 and 1996 were 36.1% and 45.5%, respectively; corresponding harvest rates for females were 0.0%, and 5.9%. Annual survival rates estimated with Kaplan-Meier for adult females, juvenile females, and cubs were 100.0%, 93.3%, and 70.3%, respectively. Maximum juvenile male survival rates were 52.0% in 1995 and 51.7% in 1996. Maximum adult male survival rates were 50.0% and 80.0% in 1995 and 1996, respectively. We monitored 31 bears for 39 bear winters with 100% of the known bears denning. Bears denned in trees (41%), rock cavities (32%), excavations (14%), snags (8%), and ground nests (5%). Chestnut oak (<i>Quercus prinus</i>; <u>n</u> = 9), red oak (<i>Q. rubra</i>; <u>n</u> = 8), and tulip-poplar (<i>Liriodendron tulipifera</i>; <u>n</u> = 1) were used as tree dens. Habitat characteristics did not differ between ground dens and tree dens; however, older bears used ground dens more frequently (<u>Z</u> = -2.484, <u>P</u> = 0.013) than tree dens. Fifty-seven percent of bears denned on public land, and we documented one instance of den reuse. / Master of Science