Management of fisheries resources is increasingly broadening its scope from single-species approaches to more holistic, ecosystem-based approaches that account for interactions of fish with a variety of ecological factors, such as predators, prey, and habitat. This ecosystem based fisheries management (EBFM) approach requires thorough biological and ecological understanding of systems pertaining to community structure, habitat suitability, and food web interactions. to strengthen the ecological underpinnings of EBFM efforts in Chesapeake Bay, the largest estuary in the USA, I conducted synoptic analyses examining the structure, function, and patterns of the bay's demersal fish community. This research relied on I0 years of data from a multi-species, bimonthly bottom trawl survey of the Chesapeake Bay mainstem. The unifying objectives of this work were to 1) synthesize basic biological and ecological information of many Chesapeake Bay fishes, and 2) examine the environmental drivers of community structure and trophic interactions in the Bay. One major hypothesis underlying the more detailed research objectives for each component was that bay-wide patterns in biomass and feeding habits of Chesapeake Bay fishes were mostly driven through bottom-up processes governed by a blend of small- and large-scale environmental factors. as food web structure and trophic interactions are governed by the presence, distribution, abundance, and behavior of species, Chapter 1 focused on evaluating patterns for these basic biological characteristics for a large suite of 50 species and investigating environmental factors that influence the community trends. Univariate and multivariate statistical modeling revealed that the demersal fish community (dominated by five species) was strongly structured along a salinity gradient, and other factors (e.g. dissolved oxygen, temperature, month, and year) helped regulate biomass and diversity trends. Chapter 2 synthesized diet information for 47 fish species, demonstrated the role of five prey groups (mysids, fishes, bivalves, polychaete worms, and crustaceans) in differentiating feeding guilds, and highlighted the importance of non-pelagic prey groups (especially the hyper-benthic mysids) in supporting the nutritional needs of fishes. Diets of 12 predator species were investigated in more detail in Chapter 3 to infer the dynamics of four important prey groups (mysids, bay anchovy, polychaetes, and bivalves) using advanced statistical modeling techniques. Results revealed generally coherent consumption trends across predators for a given prey, suggestive of prey availability driving consumptive patterns. Synchronous annual peaks in prey consumption were indicative of pulses in prey production (particularly mysids and bivalves) that were exploited by predator populations. to evaluate the population-scale effects of these bottom-up alterations in prey productivity, Chapter 4 relied on a simulation model to examine the potential effects that these annual changes in prey availability could have on consumption and production of one representative predator species. The model indicated that enhanced individual growth resulting from pulses in prey production could generate substantial gains in predator spawning stock biomass, recruitment, and fishery yield. However, the bottom-up effects on predator production had only modest effects on rebuilding times of a depleted population relative to controls on fishing mortality. This research represents one of the largest studies on community structure and trophic interactions for demersal fishes in an estuarine environment, contributing to a broader understanding of fish ecology within a complex and dynamic system. By filling research gaps identified for EBFM in Chesapeake Bay, this body of work also supports a more holistic management approach for the sustainable use of resources from the Chesapeake Bay and coastal waters of the Northwest Atlantic Ocean.

No description available.

A chemically defined synthetic medium was developed in which Phytophthora infestans (Mont.) de Bary race 1.2.4 grew extensively. This medium consisted of: 90.0 grams maltose, 20.0 grams DL-alanine, 20.0 grams L-proline, 1.0 gram KNO3, 0.5 gram KH2PO4, 0.25 gram MgSO4. 7H2O, 1.0 milligram thiamin per liter of distilled water. The average level of growth in this medium was 0.5864 gram dry weight mycelium per 50 milliliters medium. The glycoalkaloids, solanidine and solanine, were synthesized by Phytophthora infestans in the above medium with 62.5 percent of the samples positive and an overall average of 0.85 milligram total glycoalkaloids per 25 milliliters medium. The level of alkaloids detected in the medium ranged from 0.0 to 5.9 milligrams per 25 milliliters medium. No glycoalkaloid production was detected when the level of growth of the fungus was below 0.35 gram dry weight mycelium per 50 milliliters medium. Phytophthora infestans was also cultured on the following semisynthetic media: chick pea medium, rye seed medium, and lima bean medium. The fungus grew extensively in each medium, but produced alkaloids in only the chick pea medium. Fifty percent of the samples of this medium were positive for alkaloids with an overall average of 0.67 milligram total glycoalkaloids per 25 grams chick peas. Sodium salts of the macronutrients were individually substituted for the potassium and magnesium salts of the basal medium and sodium chloride and sodium acetate were singly added to the medium. Maximum growth levels were demonstrated when 0.04 percent phosphate or 0.04 percent chloride was employed in the medium. Sodium acetate was inhibitory to Phytophthora infestans. Glycoalkaloid production was significantly reduced in media containing sodium salts of the macronutrients. Regression analysis showed that the concentration of phosphate in the medium had the most influence on the level of glycoalkaloids synthesized by the fungus. Raising the concentration of phosphate in the medium resulted in increasing amounts of alkaloids being produced by Phytophthora infestans. Upon addition of micronutrients to the enriched basal medium, growth of Phytophthora infestans was stimulated by levels of ferrous iron in the concentration range of 1.0-5.0 milligram 1-1. Phytophthora infestans was inhibited by all concentrations of cobalt, copper, manganese, nickel, and by concentrations of calcium greater than 0.001 milligram 1-1. No glycoalkaloid production by Phytophthora infestanswas detected in media containing cobalt, copper, calcium, nickel, or manganese. Glycoalkaloids were produced in media containing iron at all concentrations except 5.0 milligrams 1-1 with the highest amount of alkaloids occurring in media containing 0.001 milligram 1-1. Ferrous iron seems to inhibit glycoalkaloid synthesis by Phytophthora infestans. As the level of iron in the media was increased the quantity of glycoalkaloids produced in the media declined. Studies were carried out to determine the effect of mineral nutrition on the resistance of potato foliage to infection by Phytophthora infestans. Results indicated that the level of phosphate had little or no effect on the susceptibility of potato leaflets to late potato blight. Levels of nitrate (1.0-10.0 percent) had little effect on the blight resistance of foliage, whereas higher levels of nitrate (20.0- 25.0 percent) significantly increased the susceptibility of leaflets to infection by Phytophthora infestans. Growth of common saprophytic and enteric bacteria was not inhibited by glycoalkaloids in the concentration range of 1 to 200 milligrams total glycoalkaloids per 100 milliliters.

Predation, especially by canid predators, is a significant cause of sheep loss for many producers. In recent years, the use of llamas to protect sheep from predators has gained recognition as a depredation control method. I conducted a field experiment to test the effectiveness of llamas in reducing canid predation on domestic sheep. Twenty-one llamas were placed with Utah sheep producers. Data collected from these flocks over 20 months were compared to similar data collected from flocks without llamas. Comparisons between treatment and control flocks included (l) proportion of flocks with losses to predators, (2) mean predation rates on ewes and lambs, and (3) lamb predation rate distributions. Two surveys were conducted during the study to assess producer opinions on the inclusion of llamas in their sheep management programs. In all 3 comparisons of lamb losses between treatments and controls, losses sustained by control flocks in Lambing Season l (LS l) were significantly higher than those of flocks with llamas. Among treatment flocks, losses were similar for LS l and Lambing Season 2 (LS2). Among controls, LS2 losses dropped to the level of treatment flocks. My results suggest predation may have to reach some threshold before guard llamas have an effect on losses. Results of surveys of producers with llamas indicated they support the use of llamas as guard animals for sheep.

The Forest Service faces significant climate change-related management challenges. Understanding employee perspectives on climate change will inform potential strategies to address these challenges. By analyzing data from key informant interviews and an internet survey of Forest Service employees in the Intermountain West, this study examined how Forest Service employees view and approach climate change, assessed how they perceive barriers to and opportunities for climate change adaptation within the National Forest System, and compared their perspectives across the organizational hierarchy, from district level to national policy making. The results show that although forest managers consider climate change a concern for the agency in general, they do not necessarily see how it affects the work they do personally. Although they tend to agree that climate change should be a high priority for the agency, their own ability to incorporate adaptive practices into managing a National Forest is limited by various constraints, including a lack of time, funding, and personnel, a lack of direction for on-the-ground management, and a communication gap, which has inhibited climate change-related knowledge transfer within the agency. Thus, more effective communication is needed to help forest managers see how climate change affects various aspects of forest ecosystem health in their own National Forests or districts, how climate change poses challenges to forest resilience, and what can be done to incorporate climate change considerations into their own work. The agency needs to focus on building trust, especially across its hierarchical structure, and on encouraging both vertical and horizontal information flow among employees to facilitate scientific knowledge sharing and to enhance formal and informal social networking for increased collaboration. The agency also needs to create more opportunities for district-level employees to provide feedback and get involved in climate change-related policy making, as they are a crucial source of local knowledge and experience and can be invaluable in problem-solving within the National Forest System. The insights from this study not only contribute to the Forest Service’s continuous efforts to adapt to climate change but also shed light on strategies that can be tailored by other natural resource agencies to address various management challenges within the context of global environmental change.

"Since the development of Ogden Bay Waterfowl Management Area in 1937, the Canada goose (Branta canadesis moffitti) population increased to a peak in 1949 and then declined slightly. Nelson (1954) noted that the decrease in population was probably due to either a change in habitat or increased hunting pressure. In recent years, direct band returns have indicated a high mortality rate in the population. This project was initiated to determine the relative stability of the Canada goose population and to measure, as closely as possible, the effect of a high mortality rate upon the nesting population. To estimate the stability of a goose population, three factors must be known: (1) the production rate, (2) the mortality rate, and (3) the faithfulness of homing and degree of dispersal of the population. Through knowledge of these three factors, it is possible to estimate the stability of the population, but if any management changes must be undertaken to stop the declining population, the factors that are causing the downward trend must also be understood."

The Pantanal wetland of Brazil is an important area for the conservation of jaguars (Panthera onca) and a stronghold for the species. Although our knowledge of jaguar ecology has increased since the first field studies in the mid 1980’s, a detailed study of this cryptic species remains challenging. In the following chapters, we investigated the ecology of jaguars in the southern Pantanal of Brazil. In Chapter II, we examined the foraging ecology of jaguars, documenting predation rates, patterns, and species killed. We found individual jaguars differed in the selection of their prey. There were differences in the proportion of native prey versus cattle killed by individual cats. We found that cattle (31.7%), caiman (24.4%), and peccaries (21.0%) comprised the majority of their kills. The mean predation rate on all prey for all jaguars combined was 5.1 ± 5.0 (SD) days between kills. In Chapter III, we described jaguar habitat use and spatial patterns of predation in relation to vegetation and other landscape attributes. Jaguars used some habitats disproportionatelly to their availability both in the wet and dry seasons. Forest and shrubland habitats were generally selected by jaguars. However, the type of vegetation did not have an influence on the locations of prey killed. Contrary to expectations, jaguars did not select forested habitats nor did they avoid open fields to make kills, but killed prey in these habitats proportionatelly to their availability. Our results do not support earlier findings about jaguar habitat use in the southern Pantanal but illustrate the highly opportunistic nature of jaguars. In Chapter IV, we examined space use, site stability and fidelity, movement rates, and interactions of jaguars. Our results suggested a pattern of spatial avoidance among females during the wet season. Among males, home range overlap was extensive, both in the wet and dry seasons, suggesting males did not retain exclusive ranges. Our study provided insights into the dynamic land tenure system of jaguars. Future research would benefit from radio-collaring a large number of individuals and monitoring them over a longer time span to provide a better understanding of their spatial ecology and social interactions.

The importance of actinomycetes in the soils was generally overlooked until about 1913. The investigators Hiltner and Stormer and Beijerinck began systemtaic study of their occurrence and role in soil fertility. The work done by these men and others since 1913 has proved actinomycetes to occur abundantly in most soils of the world. This work done by these men and others since 1913 has proved actinomycetes to occur abundantly in most soils of the world. This work has also proved the function of these organisms to be that of decomposing highly resistant materials such as humus and complex polysaccharide compounds. More recent work by Waksman and coworkers has established the importance of these organisms in the study of antibotics. Surveys of actinomycetes have since been made of soils in the United States and countires abroad; however, no survey has been made of soils of the great arid region of the United States. Utah soils are typical of the soils found in this region. The purpose of this study is to determine the number of actinomycetes in Utah soils in relation to the total microflora of the soil, and to appraise some of their antagonistic properties. This investigation has been primarily limited to 49 samples taken from the soils of Utah which have been studied and described by the United States Department of Agriculture.

Widespread habitat degradation and fragmentation has significantly altered the distribution and abundance of salmonids across the Western United States. To effectively conserve these fish, managers need tools to evaluate habitat quality in physically diverse streams and watersheds. Traditionally, habitat assessment for stream fish has focused on the physical characteristics of sites. Thus, such research has often overlooked important biological factors, such as the availability of prey or the presence and abundance of competitors or predators. In recent years, however, researchers have considered habitat from both physical and biological dimensions. Bioenergetics models offer a way to combine the both the biotic and abiotic characteristics of streams into one currency (i.e., energetic value) of habitat selection and habitat quality. These models take into account both physical habitat characteristics (i.e., depth, velocity, substrate, and temperature) and the availability of food from drifting insects to predict favorable locations for foraging fish, and have been extended to make reach-scale predictions of total habitat capacity. Drift-foraging, bioenergetics models are increasingly being used to evaluate habitat quality and quantity, as well as carrying capacity of the sites they are run at. However, many of these bioenergetics models have been developed and applied for salmonids at sites whose populations are well below carrying capacity. Therefore, it is essential to test the predictions of these models on populations of salmonids that are abundant. To address these concerns, I tested a bioenergetics model that Wall et al. (2016) applied to inform habitat management in the western US for cutthroat trout. I surveyed the spatial location of Bonneville cutthroat trout (BCT; Oncorhynchus clarkii utah) in the Logan River, Utah, a system where one of the most abundant populations of BCT reside, to determine if the fish were using locations with a high energetic value, predicted by a net rate of energy intake (NREI) modeling framework. I conducted snorkel surveys in both summer and fall to assess whether the modeled predictions were robust to changes in drift, temperature, or discharge. I also tested whether sampling estimates of BCT abundance were related to the NREI model predicted carrying capacity, or the proportion of suitable habitat (i.e., NREI > 0.0 J·s-1). Last of all, I tested whether the observed biomass of BCT were related to the mean NREI at each study site. I found that the majority of observed fish occupied focal positions that (i) had positive NREI and (ii) had NREI values that were significantly greater than the site mean. I also found that the simulated carrying capacity predicted for each site was significantly, positively related with the maximum BCT densities observed between 2001 and 2015 (R2=0.93, P=0.009). However, observed BCT densities and biomass were unrelated to the proportion of suitable habitat and the mean NREI at sites, respectively. I concluded that drift foraging bioenergetics models are useful tool for pin-pointing bioenergetically favorable locations within sites and discriminating capacity between sites for BCT and other similar trout species.

No description available.