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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The Metompkin Islands: A Case Study in Ownership and Management of a Dynamic Barrier System

Niebuhr, David Harold 01 January 1993 (has links)
No description available.
2

Efficacy And Unintended Outcomes Of Spatial Property Rights For Fisheries And Aquaculture Management In Chile And In Virginia, U.S.A.

Beckensteiner, Jennifer 01 January 2020 (has links)
Marine spatial property rights reduce many common pool externalities that plague wild capture fisheries and incentivize productive use for aquaculture. Specifically, Territorial Use Rights for Fisheries (TURFs) are a management tool whereby individuals or groups are granted exclusive access to harvest resources within an area, and are the prevailing management of coastal fisheries in Chile. Additionally, secured spatial property rights appear inherently obligatory for aquaculture development; i.e., private leases in Virginia, where submerged grounds granted to an individual or a company for oyster production are considered a form of TURF. Although the number and extent of spatially managed areas are the highest they have ever been in both systems, the impacts of spatial property rights on fisheries and aquaculture sustainability are still not fully understood. The objective of this dissertation was to evaluate current challenges to the effective use of TURFs, deepening our understanding of their efficacy for fishery and aquaculture management. The long-term impacts of the Chilean TURFs network on harvests of benthic resources was investigated both inside and outside TURFs (Chapter 2). Although catch rates were significantly higher inside TURFs than surrounding open access areas, they appeared to be decreasing over time, and, though limited, the impact of TURFs on catches in open access areas was negative. Spatio-temporal trends in private lease use and productivity in Virginia were examined to identify challenges faced by the oyster aquaculture industry. Constraints to aquaculture expansion were investigated by evaluating whether a lack of space limits aquaculture development as well as the extent and drivers of lease non-use (Chapter 3). Limited evidence of spatial constraints was found, although results suggest additional social and regulatory limiting factors. While rates of lease use and productivity increased from 2006 to 2016, only 33% of leases were ever used for oyster production. The non-used leases were potentially held for exclusionary or speculative uses. Additionally, Virginia had the second lowest levels of total production of cultured oysters per leased acre among the states along the U.S. East and Gulf coasts, confirming significant limitations associated with the current leasing system. Production frontier models were used to quantify lease use efficiency (i.e., utilization of space given the underlying environment) for oyster production (Chapter 4). Significant amounts of inefficiency in intensive aquaculture practices suggest that production could increase by at least 64% per lease, on average (though high heterogeneity is observed between leases). Low levels of use efficiency (i.e., underutilization) imply that leaseholders tend to lease more area than needed, likely due to the low annual lease costs and the absence of enforced production requirements. The number of leases held per leaseholder increased use efficiency, whereas leases in more populated areas were less efficiently used. This research contributes to a better understanding of TURF's efficacy and challenges in Chile and in Virginia. Overall, socioeconomic and management factors appear to be limiting productivity and sustainability of TURFs in both systems, recognizing the importance of incentives, enforcement, zoning, and the potential presence of trade-offs between economic, social and biological sustainability.
3

Recruitment Characteristics Of Juvenile Striped Bass (Morone Saxatilis) Across Recovery Periods, Year Classes, And Subestuaries Of The Chesapeake Bay

Phillips, Olivia M. 01 January 2020 (has links)
The Atlantic coast striped bass fisheries collapsed in the late 1970's due to recruitment overfishing and poor habitat quality. Recovery of the fisheries in 1995 resulted from protection of mature females, favorable environmental conditions, and several years of strong recruitment. Today, the striped bass stock is overfished. The purpose of this study was to examine recruitment characteristics of juvenile striped bass during the pre- and post-recovery periods through (1) a comparison of mortality and hatch-date distribution between periods, and (2) to examine growth metrics of individuals from the post-recovery year classes. Lengths and otolith-derived daily ages from juvenile striped bass representing three year classes (2011, 2016, and 2017) from the James and Rappahannock subestuaries of the Chesapeake Bay were used to develop subestuary-specific age-length keys. Daily ages of juvenile striped bass from 32 year classes (1986 to 2017) spanning the pre- and post-recovery periods were projected from the age-length keys. Together with count data, the projected daily ages were used to estimate instantaneous daily mortality rates (Z, day-1) for each year class. Although daily Z estimates were relatively constant among the 32 year classes, mean hatch dates shifted earlier today (1996 to 2017) than prior to 1995. Within the post-recovery year classes, daily growth in length and weight was examined along with body condition (Fulton's K). All growth metrics varied by year class and subestuary, but daily growth rates and body condition were inversely related. The results of this study indicate that recruitment dynamics of juvenile striped bass in the Virginia portion of the Chesapeake Bay have changed over time, and within the post-recovery year classes, those changes varied among fish from the James and Rappahannock subestuaries.
4

Characterizing the Biological Impacts and Human Dimensions of the U.S. East Coast Recreational Atlantic Bluefin Tuna Fishery

Goldsmith, William Morris 01 January 2018 (has links)
Atlantic bluefin tuna (Thunnus thynnus) are targeted by recreational anglers along the east coast of the United States, and the fishery is thought to be of considerable economic value. However, limited knowledge of the preferences and values of fishery participants impedes the ability of managers to maximize fishery benefits and predict harvest patterns, while an incomplete understanding of post-release mortality hinders efforts to estimate total mortality resulting from the fishery. This dissertation used a multidisciplinary approach that relied heavily on cooperative research with the recreational fishing community to examine these questions. A stated choice survey of private anglers permitted to target bluefin tuna (Chapter II) estimated a fishery consumer surplus of over $14 million in 2015 while revealing striking heterogeneity in angler preferences. Respondents placed a high value on harvesting bluefin tuna, but about half of anglers also valued non-consumptive aspects of bluefin tuna fishing such as catch-and-release. Preference segmentation was largely driven by income and recent bluefin tuna targeting behavior, with high-income anglers who had recently targeted bluefin tuna more likely to belong to the non-consumptive group. These results indicate that liberalization of harvest regulations could result in significant, non-linear increases in effort and harvest should consumptive-oriented anglers decide to re-enter the fishery. A second survey, of Atlantic bluefin tuna fishermen who possess a permit enabling them to fish either commercially or recreationally on a trip-by-trip basis, applied an online contingent sequential stated choice approach to better understand the decision-making of this unique group (Chapter III). Responses indicated that, while some permit holders consistently fish either recreationally or commercially, a substantial proportion of participants change trip type depending on fishery conditions such as prevailing fish size or regulations. The changing behavior of this latter group could potentially result in large shifts in targeting and lead to overages for the commercial handgear sector or recreational sector, and potentially the U.S. bluefin tuna quota as a whole. Lastly, post-release mortality was estimated for juvenile bluefin tuna caught in the increasingly popular light-tackle recreational fishery while also beta testing a newly developed, solar-powered pop-up satellite archival tag designed to enable large-scale, high-precision mortality studies (Chapter IV). Data were only obtained for 15 of 22 deployed tags, with 14 fish demonstrating behavior consistent with survival. One fish was predated upon, likely by a shortfin mako shark, after 17 days, and this was considered a natural rather than a fishing mortality. The low level of estimated post-release mortality, consistent with results from previous studies on different size classes of bluefin tuna caught with various angling gear types, suggests that catch-and-release angling, which Chapter II showed to be highly valued by some anglers, is a viable conservation strategy. Overall, this dissertation provides information regarding both angler preferences and fishery impacts that are of direct relevance to management. Future efforts should be directed to further engaging the recreational bluefin tuna fishing community in order to improve buy-in to management strategies and improve the ability of the United States to maintain fishing mortality within internationally prescribed limits.
5

The Wind Effects on the Evaluation of Proposed Craney Island Expansions in the Lower James and Elizabeth Rivers

Chen, Momo 01 January 2003 (has links)
No description available.
6

Artificial Illumination Of Trawl Gear Components To Reduce Pacific Halibut (Hippoglossus Stenolepis) Bycatch In The U.s. West Coast Groundfish Bottom Trawl Fishery

Jackson, Derek 01 January 2023 (has links) (PDF)
Pacific halibut (Hippoglossus stenolepis) is a prohibited species for the U.S. West Coast Bottom Trawl Fishery and in the last decade, there has been a concentrated interest in the use of artificial illumination serving as a potential bycatch reduction device. Previous studies conducted off the coast of Oregon have found that the addition of green light-emitting diodes to the bridles of low-rise, cutback trawls greatly reduced the number of Pacific halibut caught. However, recent regulation changes now permit high-rise trawls, a gear configuration that fishes a very different volume of water than the previously permissible gear profile, in areas where they were once prohibited. No study to date has investigated the efficacy of artificial illumination to reduce Pacific halibut bycatch for this configuration. Field trials for this study were conducted off the Oregon Coast during August of 2022 and were designed to test a high-rise bottom trawl fitted with artificial illumination as a means to potentially reduce Pacific halibut bycatch. Length-dependent catch comparison and catch ratio analyses for trawls with and without illumination were conducted to determine if catches of Pacific halibut and three commercially important groundfish species differ between trawl treatments. Somatic fat content of Pacific halibut and physiological indicators of stress were also assessed via blood plasma samples to determine if there was a difference in physiological condition between Pacific halibut captured in either illuminated or non-illuminated tows. Additionally, an ethogram was constructed to quantify Pacific halibut behavior in response to an approaching high-rise trawl. Analyses were based on a simulated dataset based on previous flatfish behavioral studies and qualitative evidence from video and sonar recordings collected during field trials. While illuminated trawls caught fewer individuals than the non-illuminated trawls for all species in this study, the difference in catch was not statistically significant. Total catch size was found to have a significantly positive effect on glucose and lactate levels for Pacific halibut; however, no statistically significant differences between illuminated and non-illuminated tows were exhibited across all of the physiological parameters assessed in this study. I hypothesize that this lack of difference between treatment groups may have resulted from the change in gear configuration as Pacific halibut are more likely to rise off of the seafloor when responding to an approaching net. The higher headrope orientation used in a high-rise trawl configuration may be presenting too much of a challenge for halibut seeking to avoid the path of the trawl. It is also possible that the location of the lights was insufficient in triggering a change in avoidance behaviors. These findings are contrary to prior evidence and could have potential implications for the industry. Further investigation into Pacific halibut behavior is implored.
7

Placing natural resource decisions in social and historical contexts: Sociological inquiries into agency communications, management rationalities, and community change

Geczi, Emilian 01 January 2016 (has links)
A sociological understanding of natural resource management decisions traces the links between historical change (How does this historical period differ from other periods?), society (What social relations exist at this time and how do they persist or change?), and individuals (What types of conduct and discourse prevail in this society and in this period?). The papers submitted for this dissertation examine the connections between identity, social milieu, and historical change relative to three resource management issues: (1) The promotion of nature play areas as a novel landscape form. Analysis of agency materials suggests that these spaces are advertised as bucolic settings for children's healthy development. Online and on-site communications about nature play guide both children's and adults' conduct according to specific ideas about nature, parenting, and education. (2) The sway of the instrumental rationality inherent in the ecosystem services approach to planning and management. Traditional sociological theory suggests that, for all of its promise to internalize environmental externalities in decision-making, the ecosystem services approach reduces society's capacity for engaging critically with the forces that shape our world. The recent "nonhuman turn" in social theory offers alternatives to the utilitarian ethic and quiescent character of ecosystem services. (3) The impact of changing demographics in amenity-rich towns on community wellbeing. This resident survey of four Vermont towns experiencing different rates of growth examines the utility of categories such as permanent and seasonal residents, and newcomers and longterm residents, in understanding attitudes toward community development and preservation of natural and cultural resources.
8

Analysis of Prey Selection in Black Skimmer, Rynchops niger, Adults and Chicks using Continuous Video Monitoring

Held, Renae Joyce 01 January 2003 (has links)
No description available.
9

Predicting Future Shoreline Condition Based on Land Use Trends, Logistic Regression, and Fuzzy Logic

Dingerson, Lynne M. 01 January 2005 (has links)
The lower Chesapeake Bay and adjacent coastal waters serve as the primary summer nursery areas for juvenile sandbar sharks (Carcharhinus plumbeus) in the Northwest Atlantic Ocean. The large population of juvenile sandbar sharks in this ecosystem benefits from increased food availability that fuels rapid growth and from limited exposure to large shark predators. Juvenile growth and survival is the most critical life history stage for sandbar sharks, and juvenile nursery grounds will continue to play an important role in the slow recovery of this stock from severe population declines due to overfishing. The goal of this study was to assess the possible impacts of juvenile sandbar sharks as apex predators on the lower Chesapeake Bay ecosystem and to evaluate the energetic benefits of using this nursery. The bioenergetics model was used as a tool to predict energy consumption rates of individual sandbar sharks based on their energetic demands: metabolism, growth, and loss of waste. Metabolic rate is the largest and most variable component of the energy budget, particularly for species such as the sandbar shark that must swim continuously to ventilate their gills. The standard (basal) and routine metabolic rates of juvenile sandbar sharks were measured in two laboratory respirometry systems, using oxygen consumption rate as a proxy for metabolic rate. These data span the entire range of body sizes and water temperatures characteristic of the Chesapeake Bay population. Standard metabolic rates of sandbar sharks were similar to values obtained for related shark species by extrapolation of power-performance curves. The effects of body size and temperature on standard metabolic rate were similar to previous results for elasmobranchs and teleost fishes. In fifteen sharks, routine metabolic rate while swimming averaged 1.8 times the standard metabolic rate when the sharks were immobilized. Data obtained from the literature support the theory that limited gill surface areas and narrow metabolic scopes of many elasmobranchs help to explain their slow growth rates, since growth has the lowest rank of the multiple metabolic demands placed on the oxygen delivery system. These new metabolic rate data were then combined with other species-specific data to construct a bioenergetics model for juvenile sandbar sharks for the time they spend in Chesapeake Bay each summer. This model predicted higher daily rations than previous estimates for this species that were based on simple bioenergetics models or stomach contents and gastric evacuation rate models. However, the predicted rations agree with reconstructed meal sizes of juvenile sandbar sharks and are comparable to those of ecologically similar shark species. When extrapolated from individuals to the population level, the model predicted a negligible effect of predation by juvenile sandbar sharks on the lower Chesapeake Bay ecosystem; the consumption rate of juvenile sandbar sharks pales in comparison to other carnivorous fishes and to humans, the true apex predators in the system.
10

Survival in an Urbanized Landscape: Radio-Tracking Fledgling Eastern Bluebirds (Sialia sialis) on Golf Courses

Jackson, Allyson Kathleen 01 January 2010 (has links)
No description available.

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