Self-recruiting species (SRS) are the aquatic animals that do not require repeated stocking in farmer managed aquatic systems (FMAS) and can be of indigenous or exotic origin (Little, 2002). Current concept of conventional aquaculture greatly underestimated the contribution of SRS to the livelihoods and particularly nutritional security of the poor. The present study examines the role of SRS in poverty focused aquaculture. The role of SRS in aquaculture was evaluated from the perspective of people dependent on them in terms of well-being, gender, resource access and broader livelihoods in the northwest and south-central region of Bangladesh. SRS management practices, already an existing component of aquaculture in FMAS, were explored to define sustainable management strategies that benefited poor. The thesis uses a livelihoods framework within a methodological context of participatory action research at household, community and national level. The process begins with a Participatory Community Appraisal (PCA) in 18 communities with 360 participants which then directs further investigation at household level through survey, longitudinal study farmer and farmer participatory action research over a systematic 4 year investigation from 2001 to 2004. At the PCA stage, the context of livelihoods, importance of popular aquatic animals and their different sources were examined. The more frequently mentioned and higher scored SRS by the communities were Clarias batrachus, Anabas testudineus, Macrobrachium sp., Puntius sp., Heteropneustes fossilis, Channa punctatus, Mystus vittatus, Amblypharyngodon mola, Channa striata, Macrognathus puncalus. The sources of these aquatic animals provided a better understanding of the diverse typology of farmer managed aquatic systems (FMAS) and showed the importance of both FMAS and open systems to sustain a self-supporting population of aquatic animals for nutritional security of the poor. Rice and other crop farming, fish culture, livestock and poultry rearing, service and business were found to be common occupations among better off households where as share-cropping, petty trade, fishing, selling agricultural and non-agricultural labour were of greater importance to poorer households. Both gender and well-being affected livelihoods with significant differences in involvement of the better off and poorer. PCA findings were later validated at a national level stakeholder workshop with 138 government, non-government officials, researchers and academics which established a broader understanding of the prospects and constraints of SRS culture and conservation. The baseline survey with 119 households further examined the characteristics and access of key farmers to managed aquatic systems, livelihood assets, vulnerability and the behaviours of households managing SRS. Access to FMAS and SRS are of much greater importance to poorer than to the rich. Positive, negative and neutral attitudes towards managing SRS were not significantly affected by well-being. Access to appropriate types of FMAS, SRS management knowledge, traditional taste, greater involvement in non-farm activities, family need were all associated with the SRS positive attitude. Results from the year round longitudinal study with 50 households focused on the seasonal dynamics of food consumption and its connection to livelihoods in terms of sources, income and expenditure. Aquatic animals are the 3rd most important contributor to the rural Bangladeshi diet after cereal and vegetables by weight and the 2nd most important contributor by price after cereal. FMASs are important source of aquatic animals compared to other sources such as open system, market and given sources (free from neighbours and relatives). SRS were accounts for 52% of the total aquatic animal consumption. Even among some very low income vulnerable groups such as day labourers and rickshaw pullers, SRS was found important in their diet. Poorer households rely significantly more on SRS than richer households. The total amount of SRS consumed by thenhosueholds over the year was strongly correlated with total number of SRS species consumed per year and further emphasised the significance of maintaining biodiversity. The pre monsoon dry period as April and May were low consumption periods in both zones. Rainy and post rainy season July to October were the peak consumption months in the northwest zone and June to November in south-central zone. The year round farmer participatory trial with 29 farmers confirmed the value of SRS within culture systems with lack of any major conflicts in the husbandry of non-stocked species with popular carps in the system which, in the past regarded as weed fish and have been generally excluded from formal aquaculture. The study found a range of species of both commercial and non-commercial SRS have greater significance to the poor than to the richer households particularly in terms of household consumption, income and social value. More deliberate attention towards avoidance of negative actions towards SRS in aquaculture in the lean season may also expand niche benefits for non-pond owners and vulnerable social groups such as fishers. Current investigations also revealed the complementarities of stocked fish particularly during dry months when SRS are less available. In spite of the poor having limited access to ponds, the seasonal scarcity of water in dry seasons and habitat degradation, SRS remains an important and valuable food item for the poor in low income vegetable scarce months. The study recommends future emphasis on the management and conservation of both commercial and non-commercial (mainly for consumption) SRS in FMAS particularly during the lean season and also to maintain the integrity of the permeable nature of FMAS and its linkage with the broader open systems for the sustained availability of such self-recruiting population. Finally the study greatly influenced the perception of utilising both stocked and non-stocked species in formal aquaculture. It is necessary to take urgent steps to avoid negative actions to damage SRS and formulate an integrated approach to water, agriculture, environment and fisheries management to sustain them for current and future nutritional and livelihoods security of the poor.

This study describes the delineation of appropriate sites for aquaculture using remote sensing, GPS and GIS. A 1996 composite Landsat TM image covering the south-western part of Bangladesh was used to identify water bodies, the extent of brackish water and associated land use features in the image. The Remote Sensing image was complemented by digitised secondary data from a range of sources, including hard copy maps to produce a GIS database which included environmental layers such as water bodies, rivers, soils, land use, temperature, rainfall, salinity and pH. The database also included infrastructural issues, such as roads, railways, processing plants, towns and cities. A series of GIS models were developed in order to identify and prioritise the most suitable areas for freshwater prawn, tilapia and carp and brackish water shrimp and crab farming. A range of scenarios for land allocations were used to develop a series of resource use models linked to likely production outcomes. Global warming and accelerated sea level rise is considered in the study area with different sea level rise scenarios of 50, 100, 150 and 200cm. The consequence of land losses and displacement of the population from the area in different situations is discussed. The economic characteristics of shrimp farming and alternative land uses in the Khulna region were also considered. Five land use options were studied based on economic output and job potential. Among these, brackish water shrimp and crab culture, moderately saline tolerant tilapia and prawn culture, fresh water carp culture and traditional rice production systems, and fresh water prawn culture performed best followed by brackish water shrimp and crab culture. This study showed the extent of potential for aquaculture in the Khulna region and further demonstrates the usefulness of GIS as an aquaculture-planning tool. Model programming was also found to be very useful tool to enabling regenerating of multiple scenarios very quickly. Overall, GIS modelling associated with remote sensing has great potential for informed decision-making in aquatic production systems and optimising management of natural resources in a region where they are already under considerable pressure. The implications for use of these systems in reducing land use conflict and sector planning for the region are discussed.

To monitor and assess direct anthropogenic impacts on an aquatic system requires knowledge of its natural variation. The goal of this study explored natural variation in the lake fish communities of the northern Bruce Peninsula, which may act as a reference condition for other studies. The results of this study indicated there has been a shift towards more small-bodied, native species present in the fish communities, potentially a result of beaver activity in the area. A second goal was to calculate gear sampling efficiencies to enable the design of efficient monitoring protocols for fish communities in small, shallow lakes. It was concluded that a wide variety of gears are required to assess the fish species composition in a lake. Fine-mesh hoops were the most effective gear; however, saturation was never obtained for boat electrofishing; therefore, additional research is required to determine effectiveness relative to the fine-mesh hoop net.

Identifying the ecological mechanisms that determine food web structure is critical for understanding the causes and consequences of diversity. The objective of this thesis was to identify the mechanisms structuring aquatic food webs across environmental gradients from a multi-level perspective (individual to ecosystem) using integrative methodology and field experiments to test classic ecological theory. My results demonstrate support for the dynamic constraints hypothesis, which predicts habitats with greater disturbance should have shorter food chains, but are not consistent with the ecosystem size hypothesis that predicts larger ecosystems have longer food chains. Insect and amphibian richness increased with increasing pond size and hydroperiod, indicating that insertion of new consumers into pond communities was driving variation in food-chain length. A multivariate analysis testing the influence of physicochemical variables on food-web characteristics revealed that hydroperiod and pond area had a strong influence on amphibian and invertebrate assemblages, trophic diversity and 15N range. Food-chain length did not respond strongly to any one variable, but instead responded weakly to multiple environmental variables, suggesting interacting influences on food-web structure. Conversely, the trophic niche of amphibian larvae was not influenced by pond hydroperiod, but did exhibit ontogenetic diet shifts. Populations of amphibian larvae with broader niche widths also had increased individual variation, supporting the niche variation hypothesis. In addition, I assessed whether species diversity influenced the magnitude of cross-habitat resource flow between aquatic and terrestrial habitats via emerging aquatic insects, metamorphosing amphibians, and litter deposition. Deposition into ponds far exceeded carbon exported via insect and amphibian emergences. We found a negative relationship between resource flux and the diversity of amphibians and insects, which contradicts the general pattern of positive biodiversity-ecosystem function relationships. My research strongly suggests environmental variation is a key process in shaping food-web structure and function and that multiple methodologies are needed to understand temporal and spatial dynamics of aquatic ecosystems.

To monitor and assess direct anthropogenic impacts on an aquatic system requires knowledge of its natural variation. The goal of this study explored natural variation in the lake fish communities of the northern Bruce Peninsula, which may act as a reference condition for other studies. The results of this study indicated there has been a shift towards more small-bodied, native species present in the fish communities, potentially a result of beaver activity in the area. A second goal was to calculate gear sampling efficiencies to enable the design of efficient monitoring protocols for fish communities in small, shallow lakes. It was concluded that a wide variety of gears are required to assess the fish species composition in a lake. Fine-mesh hoops were the most effective gear; however, saturation was never obtained for boat electrofishing; therefore, additional research is required to determine effectiveness relative to the fine-mesh hoop net.

No description available.

The hypothesis that aquatic biomass is uniformly distributed over logarithmic size classes was evaluated with samples from epilimnetic plankton communities. Although the hypothesis is true for oligotrophic lakes, biomass increases between successive size classes in mesotrophic and eutrophic lakes. The abundance of organisms in logarithmic size intervals is strongly negatively correlated with size. The relationship between organism size and physiological performance in mixed communities was examined by testing the hypothesis that limnoplankton respiration rates are predictable functions of mean body size. The equation governing this relationship was found to be similar to those obtained with laboratory cultures. The total epilimnetic phosphorus concentration is correlated with both biovolume and respiration rate. Many limnological relationships, including those established in this thesis, are based on linear regressions between log-transformed variables. The rules for the correct use of backtransformed predictions are elucidated. A theorem is proven, which sets limits to the relationship between the coefficients of determination on the original and transformed scales. Simulated data and empirical results are used to illustrate the applications and limitations of the theoretical results.

In fünf Fließgewässern Sachsens wurde die Wirkung von Baumaßnahmen der Landestalsperrenverwaltung auf die Lebensbedingungen für Fische begutachtet. Bewertet wurde der Rückbau von Wehren, der Einbau von Fischaufstiegsanlagen sowie Renaturierungsmaßnahmen mit Strukturverbesserungen der Gewässersohle. Die Maßnahmen in der Triebisch, der Müglitz, der Wesenitz und der Kleinen Spree verbesserten die Lebensbedingungen und Wandermöglichkeiten für Fische. Die komplexen Baumaßnahmen in der Chemnitz inmitten des Stadtgebiets bewirkten bislang noch keine Verbesserungen.

Thesis (M.S.)--University of Hawaii at Manoa, 2007. / Includes bibliographical references (leaves 69-76). / x, 76 leaves, bound ill. (some col.), col. map 29 cm

Bibliography: p. 171-181. / xxiii, 181 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The comparision of the pond and field plants suggests both species are eminently more suited to static water regime where adaptations by the plant can be made effectively to help with the problem of oxygen transport. The results also suggest that plants experience a variable and static water regime differently. / Thesis (Ph.D.), University of Adelaide, Dept. of Botany, 1999