Some fisheries management activities have clearer relationships with angler consumption than others, end the clarity is usually reflected by the amount of historical data available upon which to base the relationship. Adequate historical data exists to derive the relationships between angler-days and access development, water development, regulation changes, and catchable trout stocking, so these relationships are probably the most reliable in PISCES. Little historical data exists to assess the effects of research and information and education activities upon angler-days. Therefore, the segments of PISCES accounting for research and information and education are probably the least reliable parts of the model. PISCES can be improved before it is utilized in decision analysis. First, the efficiency of the computer program could be improved. PISCES is functional, but computer time and storage space might be saved by altering the program. Second, sensitivity analysis of input variables would provide important information to future users of PISCES. And finally, an application study would reveal any unforeseen problems which might arise in using PISCES. If PISCES is never used to formulate management decision policies, it is hoped that some of the modeling techniques employed will prove useful in future efforts to model natural resource systems. / Master of Science

Current rates of extinctions are estimated to be around 1000 times higher than background rates that would occur without anthropogenic impacts. These extinction rates refer to the traditional view of extinctions, i.e. numerical extinctions. This thesis is about another type of extinctions: functional extinctions. Those occur when the abundance of a species is too small to uphold the species’ ecologically interactive role. I have taken a theoretical approach and used dynamical models to investigate functional extinctions and threshold values for species’ mortality rates in ecological networks. More specifically, I have derived threshold values for focal species mortality rates at which another species or the focal species itself goes numerically extinct (Paper I-II), or transgresses some predefined threshold abundance (Paper III). If an increased mortality rate of a focal species causes another species to go numerically extinct, the focal species can be regarded as functionally extinct, since its abundance is no longer large enough to uphold its ecologically interactive role. Such functional extinctions are investigated in the first papers (Paper I-II). In the following paper, limits for both increased and decreased mortality rates of species are explored (Paper III). Paper III also extends the basic theoretical idea developed in paper I-II into a more applied setting. In this paper I develop a time series approach aimed at estimating fishing mortalities associated with a low risk that any species in a community transgresses some predefined critical abundance threshold. In the last paper (Paper IV) the community wide effect of changes in the abundance of species is investigated. In the first paper (Paper I) I investigate threshold levels for the mortality rate of species in ecological networks. When an increased mortality rate of a focal species causes another species to go extinct, the focal species can be characterized as functional extinct, even though it still exists. Such functional extinctions have been observed in a few systems, but their frequency and general patterns have been unexplored. Using a new analytical method the patterns and frequency of functional extinctions in theoretical and empirical ecological networks are explored. It is found that the species most likely to be the first to go extinct is not the species whose mortality rate is increased, but instead another species in the network. The species which goes extinct is often not even directly linked to the species whose mortality rate is increased, but instead indirectly linked. Further, it is found that large-bodied species at the top of food chains can only be exposed to small increases in mortality rate and small decreases in abundance before going functionally extinct compared to small-bodied species lower in the food chains. These results illustrate the potential importance of functional extinctions in ecological networks and lend support to arguments advocating a more community-oriented approach in conservation biology, with target levels for populations based on ecological functionality rather than the mere persistence of species. In Paper II I use the approach developed in Paper I to explore the frequency and patterns of functional extinctions in ecological networks with varying proportions of mutualistic and antagonistic (predator-prey) interactions. The general results from Paper I are also found in Paper II; that is, an increased mortality rate of one focal species often first leads to an extinction of another species rather than to an extinction of the focal species itself. Further, the frequency of functional extinctions is higher in networks containing a mixture of interaction types than in networks with only antagonistic interactions. Overall, this study generalize the findings of paper I for networks containing a variety of interaction types. To make the theoretical approaches developed in paper I-II operational in a management setting I develop a time series approach aimed at estimating ecologically sustainable fishing mortalities in a multispecies fisheries context (Paper III). An ecologically sustainable fishing mortality is here defined as a long-term fishing mortality associated with a multispecies objective which infers a low risk that any species, either the focal species itself or another species, in a community transgresses a critical biomass limit, below which the risk of recruitment failure is high. The approach is exemplified using a statistical food web model of the dominating fish stocks in the Baltic Sea. For the most abundant fish stock a counterintuitive result is found; it is more likely that the multispecies objective is met if its mortality caused by fishing is increased compared to if it is decreased. Further, simultaneous changes of the fishing mortality of a number of interacting species in the food web model shows a much narrower region of possible sustainable fishing mortalities than a single species approach, something that is not captured by current stock assessment models. Altogether these results are governed by indirect effects propagating in the community and pinpoints the need to adopt community dynamical approaches in fisheries management. The population sizes of many species in the world are declining. Negative population trends are particular pronounced in large-bodied herbivores and carnivores, species known to play important regulatory roles in many ecosystems. Although this indicates that the ecological consequence of declining populations of species might be profound, its impact on ecosystem stability remains largely unexplored. In paper IV it is therefore explored how declining populations of rare and common species affects the resilience – recovery rate – of ecological networks. An analytical approximation shows that network resilience is a function of the harmonic mean of the species’ abundances. This means that network resilience is especially sensitive to declining abundances of rare species. Consistent with this analytically derived result, a clear and positive relationship between resilience and the abundance of the rarest species in a broad spectrum of dynamical models of ecological networks is found. Together these results illustrate the potentially negative consequences of declining populations of rare species for the stability of the ecological systems in which they are embedded, and provide ecological arguments for the protection and management of rare species.

No description available.

A simulation and decision-support software product for aquaculture facility design and management planning is described (AquaFarm, Oregon State University��), including comprehensive documentation and applications to practical problems. AquaFarm provides (1) simulation of physical, chemical, and biological unit processes, (2) simulation of facility and fish culture management, (3) compilation of facility resource and enterprise budgets, and (4) a graphical user interface and data management capabilities. These analytical tools are combined into an interactive, decision support system, for the analysis and development of facility design specifications and management strategies. Intended user groups include aquaculture research, engineering, education, and production. As guided by the user, aquaculture facilities can be of any type, configuration, and management objectives, for purposes of broodfish maturation, egg incubation, and/or growout of finfish or crustaceans in cage, single pass, serial reuse, water recirculation, or solar-algae pond systems. User-accessible specifications include (1) site climate and water supplies, (2) components and configurations offish culture systems, (3) fish and facility management strategies, (4) unit costs for budget items, (5) production objectives (species, time schedules, and fish numbers and weights), and (6) parameters of unit-process and fish performance models. Based on these specifications, aquaculture facilities are simulated, resource requirements are compiled, and operation schedules are determined so that production objectives are achieved. Facility performance is reported to the user as management schedules, summary reports, resource and graphical compilations of time-series data for unit process, fish, and water quality variables. If unsatisfactory resource requirements or unattainable production objectives are found, procedures of iterative design and management refinement are supported. To provide this analytical capacity, a wide range of existing and newly developed, quantitative methods and models are assembled and synthesized into an integrated analytical framework, including aquatic chemistry, aquatic biology, fish biology, aquacultural engineering, and simulation techniques. Unit-process and system-level validation exercises are demonstrated for a wide range of aquaculture facilities, in which (1) facilities are constructed according to reported studies, (2) simulation trials are accomplished, and (3) good agreement between predicted performance and empirical observations is demonstrated, given that sufficient specification of site-specific variables is provided. / Graduation date: 2000

Characterization of distinct angler fishing styles (e.g., how, where, and with what) allows resource managers the ability to predict how perceived impacts or modifications to fisheries resources (i.e., decline of fish species population) may impact different user groups. Recreation specialization provides a useful framework for understanding participation diversity among recreationists in terms of unique styles of participation. Bryan suggested that within an activity distinct types of participants exist that demonstrate characteristic styles of participation. Fundamental to Bryan's development of specialization were contextual attributes that characterize participant engagement in a recreation activity. However, advancement in specialization has been accompanied by a departure from Bryan's original conceptualization describing activity context. I revisited how specialization is operationalized and developed a contextual style of participation typology and self-classification measure to investigate displacement and substitution behavior among Texas inshore fishing guides. Data were collected in two separate phases. In 2010, I conducted an exploratory investigation that included eighteen face-to-face, in-depth interviews with key informants spanning the entire coast. In 2011, I conducted a quantitative investigation that included mailing a 12 page self-administered survey to all Texas Parks and Wildlife licensed saltwater fishing guides (n=909). Thematic analysis drawing on grounded theory revealed that the salience of six contextual attributes (i.e., bait type, tackle type, fishing method, casting tactic, water depth, and fish species) that characterized four distinct styles of participation (e.g., Bait, All-purpose, Lure, and Sight-casting Guides). A unidimensional self-classification measure was developed based on my guide typology and discriminant analysis revealed it performed as well as a multidimensional measure of specialization. Ultimately, analysis of variance revealed significant differences existed among self-classification categories with respect to substitution behavior (e.g., targeting alternative species of fish, fishing in another location, and using alternative fishing methods or bait types) due to perceived spotted seatrout declines during 2010. In short, my findings suggest that anglers respond differently due to perceived spotted seatrout declines based on their preferred contextual style of participation. A contextual approach to understanding style of participation provides fisheries managers an effective method for understanding and mitigating social and ecological issues.

In 1988, the red snapper fishery in the Gulf of Mexico was declared severely overfished. Since then, the daily bag limit has been reduced from 7 to 2, the minimum size limit has increased from 13 to 16 inches, and the year-round recreational season has been reduced to one lasting 53 days. Despite NOAA's recommendations that the Gulf States match these regulations, Texas has enforced a 4 bag limit and no seasonal restrictions. In 2009 alone, the total recreational catch exceeded the allocated quota by 1.7 million pounds. The lack of consistency between state and federal regulations and the drastic changes in management schemes have affected anglers' confidence in management, and limited the ability of the fishery to successfully adapt. This study provides an innovative assessment that measures fishers' knowledge and determines their support for current fishery regulations and for the scientific rationale behind the regulatory system. Over 150 interviews of red snapper anglers at charter and head boat docks were conducted along the Texas coast. The majority of respondents were 20-50 year old (74.5%), male (89.3%), four-year college graduates (34.9%), who resided near the coast (65.3%), and were targeting red snapper (92.5%). Results showed that 72.5 percent of respondents agree with the science behind red snapper management, 63.4 percent believe that the stock has improved since 2008, 89.5 percent agree that a bag limit in general is an appropriate management tool, and 78.2 percent agree with the Texas state management of red snapper. However, 51.7 percent of respondents disagree with the federal management of red snapper, and 90.1 percent of all respondents did not know that red snapper live to be 41-60 years old. The lack of support for the federal management may be due to the lack of knowledge of red snapper life span. Applications of this research will be imperative for managers - who already address biological, ecological, and economic aspects of a fishery - to expand their multi-disciplinary approach to include social analysis for the successful evolution of recreational fisheries management. Future research should explore improved management approaches that involve greater communication between the stakeholders and managers.

Taiwan's surrounding waters rich in terrain, and a number of shares of the sea converge along the coastal waters of Taiwan created a rich fishing ground.However, due to excessive fishing efforts to longterm investment , But lack of proper management of fitness , so even though the number of vessels increased, but the overall fishery production continued to decrease. The management of fisheries resources requires the correct results as the scientific basis for resource assessment , before they can properly apply effective management to achieve goals , and resources conservation and use of a balance between fisheries. The correct resource assessment,you need detailed information on the basis of the catch,the most important time, space and other efforts to catch the amount of information is the most common practitioners of business operating statements made . Taiwan's coastal fisheries,as yet mandatory for the industry to report their operating statements provided management measures , so in the past this type of information is achieved through the visits, but the mission is not only the high cost of information , a small number and accuracy is not high also limited to the funding and cooperation from the fishermen often intermittent , resulting in a serious ack of resources and ssessmenta information. Taiwan Caost Guard Administrstion in order to monitor the waters around Taiwan ,the dynamic vessel offshore the coast of Taiwan are build Caost Radar Systems.These systems approach to proactive scanning , within 24 hours for the scan to monitor vessels and left navigation records including the vessel name , time location information of the vessel .These data separated by fishing information , speed of calculation,it is possible to estimate the fishing vessels fishing effort in the future with the sale of the ships coming into port unloading data information on fishing operations as an alternative complementary information on the shortcomings of the report did not work . The purpose of this study , that Caost Radar Systems in the use of bank information obtained , isolated fishing information , conduct analysis and calculation , and the actual data for verification visits to explore the application of Caost Radar Systems on shore along the coastal fisheries management feasibility . The results showed : Caost Radar Systems data from the isolated shore fishing vessels that the correct information to the operating position, and velocity analysis based on fishing operations , can estimate fishing effort,and calculate the frequency of operating out of position, draw fishing boats operating region .But the study also found the sea wave and blind area factor will be off the lock occur ,resulting in boat speed and position information a short time gaps , but this does not affect the overall assessment of fishery resoures, through projections to supplement the information in this section.

Aquatic vegetation management and fisheries management are inseparable, however conflicts are often perceived between the two. We investigated the impact of biological, chemical, and no vegetation control on the ecology of private impoundments stocked with largemouth bass and bluegill sunfish. The primary purpose of this study was to determine if aquatic vegetation management had significant impact on pond ecology. A secondary purpose of this study was to collect data for a separate descriptive study on the impact of vegetation management on plankton populations. Nine 0.10 acre ponds were obtained at the Aquaculture Research and Teaching Facility of Texas A and M University in the fall of 2005. Southern naiad (Najas guadalupenis) was transplanted into each pond at a stocking rate of one ton per surface acre. One of three treatments was then randomly assigned to each pond. The treatments were replicated three times and consisted of: an herbicide treatment using Reward and Cutrine, a triploid grass carp treatment, and a control treatment. Fathead minnows (Pimephales promelas), bluegills (Lepomis macrochirus), and largemouth bass (Micropterus salmoides) fingerlings were stocked in each pond. The treatments were initiated on May 31, 2006. Prior to the initiation of the treatments, sampling of each pond occurred for hardness, total phosphorus, nitrite, nitrate, ammonia-nitrogen, dissolved oxygen, turbidity, pH, and temperature. Macroinvertebrate samples were collected from each pond. Post-treatment sampling was conducted on the herbicide treatment and the control at day 2, day 7, day 14, day 28, and monthly thereafter. Posttreatment sampling on the triploid grass carp treatment was conducted at day 14, day 28, and monthly thereafter. One-way ANOVA tests were conducted on the data using SPSS 15.0, and multivariate analysis was conducted using CANOCO software. Significant differences between treatments were found for the parameters turbidity, macrophyte percent coverage, macroinvertebrate species richness, largemouth bass mean weight, and largemouth mean length. Herbicide application and grass scarp stocking significantly decreased the percent coverage of macrophytes in the ponds. Turbidity was significantly increased in the herbicide and grass carp treatments. Largemouth bass mean weight and length were significantly higher in the grass carp ponds. No significant relationships were found in the multivariate analysis; however, there appeared to be several trends within the multivariate analysis that provide insight into potential ecological relationships between the various parameters. The results of this study provide great insight into the impact that various aquatic vegetation management strategies have on the ecology of small impoundments and will help private pond owners and managers conduct better pond management when dealing with aquatic vegetation problems.

Marine reserves are promising tools for fisheries management, and are especially suited for complex, multi-species fisheries. Recent work has focused on the design of reserves to achieve particular management objectives and on defining appropriate indicators for monitoring to determine whether these objectives are being met. In principle, there should be a strong correlation between biological, social and economic indicators that are all correlated with fish abundance and ecosystem health. In practice, different indicators are often inconsistent, and it is common for researchers and fishers to have conflicting opinions on how well reserves are meeting management goals. I suggest that these discrepancies are not necessarily due to conflicting opinions regarding management objectives, but rather that the inherent biases in different sampling schemes may cause different measures of the same parameter to be uncorrelated. For example, scientists tend to sample only snapshots in time and space in randomly chosen locations, while fishers sample over much greater temporal and spatial scales but in non-random locations. Furthermore, marine ecosystems are extremely complex, and failing to account for the full extent of this complexity may lead to erroneous measurement of biological trends. The purpose of this dissertation is to determine the causes of discrepancies between different types of indicators using a multidisciplinary approach. A detailed study of the Glover’s Reef Marine Reserve (GRMR) in Belize provides a basis for comparison. Chapters 2 to 4 of the dissertation focus on understanding how the GRMR has functioned to produce fisheries benefits, and elucidating some of the factors responsible for variation in species’ responses to reserve protection. Chapters 5 to 7 of the dissertation focus on comparisons of different indicators of changes in fish abundances, and explain the circumstances under which indicators may disagree. With a better understanding of the functioning of the GRMR based on both scientific and local knowledge, efforts can be made to develop more appropriate indicators, and these indicators can then be tested for use in other coral reef reserves worldwide.

Research Doctorate - Doctor of Philosophy (PhD) / Shrimp farming and capture fishery are two of the major industries of Can Gio district, Ho Chi Minh City, southern Vietnam. These industries have recently developed and contributed to the improvement of local economy. However, they have also raised environmental concerns regarding water pollution and fish stock depletion. The negative impacts of shrimp farm effluents on the water quality of mainstream rivers and fish communities have not been studied in Can Gio. Additionally, there is a lack of research on the influence of the current fisheries management on environmental protection and fish conservation in this district. The goal of this study was to address key issues in fisheries management in Can Gio in regard to the impacts of wastewater from shrimp farming on the water quality of mainstream rivers that affect the local fish communities, and the influence of improper fishing practices that lead to the depletion of local fish stocks. This study also aimed to propose strategies to improve the local fisheries management for more environmentally responsible productions. Two mainstream surveys were developed to obtain data, i.e. environmental surveys for the assessment of water quality and pollution impacts on fish communities; and people interviews for the examination of fisheries management related to shrimp farming and fishing practices. The findings were used as a baseline to develop appropriate strategies for improving the management in terms of promoting sustainable productions both in shrimp farming and capture fishery industries and protecting the environment. This study found that shrimp farming, especially intensive farms have contributed to water pollution in mainstream rivers in Can Gio, and in turn the water pollution has adversely affected the local fish communities. The waters adjacent to the intensive farms were contaminated with high concentrations of organic matter. The number of fish species reduced and tolerant species appeared at higher proportions in these areas. Many improper practices in shrimp farming and fishing as well as weaknesses in government management were addressed to be the key issues leading to environmental pollution and fish depletion. The proposed strategies focused on improving the management at both government and community levels. Promoting community-based management was suggested as a key to the success in fisheries management in Can Gio.