105 resultados para large-small scale (LSS) equations of turbulence

em Aquatic Commons


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In recent decades, hatchery-growout culture of oysters, Crassostrea virginica, and northern quahogs, Mercenaria mercenaria, has been commercially successful in Atlantic United States and oysters in Atlantic Canada. Culturists have not had success, as yet, with northern bay scallops, Argopecten irradians irradians. Large mortalities occur during the culture process, mainly because the scallops are relatively delicate and some die when handled. In addition, too little edible meat, i.e. the adductor muscle, is produced for the culture operation to be profitable. However, three companies, one in Massachusetts, one in New Brunswick, and one on Prince Edward Island, Canada, have discovered that they can produce bay scallops successfully by harvesting them when partially-to fully-grown and selling them whole. In restaurants, the scallops are cooked and served with all their meats (adductor muscles and rims) and also with the shells, which have been genetically-bred for bright colors. The scallop seed are produced in hatcheries and then grown in lantern or pearl nets and cages to market size. Thus far, production has been relatively small, just beyond the pilot-scale, until a larger demand develops for this product.

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The inadequate supply of tilapia seed is considered as one of the major present constraints to the development of the culture industry in Nigeria. The floating bamboo net-hapa hatchery/nursery system was observed to be very efficient in the mass production of tilapia (Oreochromis niloticus) fry and fingerlings at Kainji Lake Research Institute. This system was therefore, recommended for small-scale (artisanal) commercial operators consisting of fishermen families in order to increase their productivity and hasten development of rural communities. The economic analysis of this system showed that loan obtained for the recommended scale of operation can be amortized within 2 years of the project. It was emphasized that the operational and managerial skills of the fish farm operators account largely to the production cost and profitability of the enterprise

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This paper discusses the investment prospects in Tilapia fry and fingerling production in raceways created from the concrete drainage channel of a reservoir or pond of an existing fish farm in Nigeria. With an initial capital of 1,300 and an annual operating cost of 310 spent on procurement of fish feed and brood stock for a 10 m super(2) raceway per se, a net profit of 4,100 and 5,090 would be realized from Sarotherodon galilaeus in the first year and subsequent years of production respectively, assuming that the fingerling production rate has been maintained through the production period. It is concluded that the application of this approach of optimizing the use of available resources in the fish farm for the productive breeding of Tilapia fry and fingerlings will apart from alleviating the problem of scarcity of stocking materials in the country, increase the profit margin accruing to the fish farmer

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Despite considerable conservation efforts, many reef fish fisheries around the world continue to be in peril. Many are vulnerable to overexploitation because they have predictable and highly aggregated spawning events. In U.S. Caribbean waters, fishery managers are increasingly interested in advancing the use of closed areas as a means for rebuilding reef fisheries, protecting coral reef habitats, and furthering ecosystem-based management while maintaining the sustained participation of local fishing communities. This study details small-scale fishermen’s views on the Caribbean Fishery Management Council’s proposals to lengthen the current Bajo de Sico seasonal closure off the west coast of Puerto Rico to afford additional protection to snapper-grouper spawning populations and associated coral reef habitats. Drawing on snowball sampling techniques, we interviewed 65 small-scale fishermen who regularly operate in the Bajo de Sico area. Snowball sampling is a useful method to sample difficult-to-find populations. Our analysis revealed that the majority of the respondents opposed a longer seasonal closure in the Bajo de Sico area, believing that the existing 3-month closure afforded ample protection to reef fish spawning aggregations and that their gear did not impact deep-water corals in the area. Whilst fishermen’s opposition to additional regulations was anticipated, the magnitude of the socio-economic consequences described was unexpected. Fishermen estimated that a year round closure would cause their gross household income to fall between 10% and 80%, with an average drop of 48%. Our findings suggest that policy analysts and decision-makers should strive to better understand the cumulative impacts of regulations given the magnitude of the reported socio-economic impacts; and, more importantly, they should strive to enhance the existing mechanisms by which fishermen can contribute their knowledge and perspectives into the management process.

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The small-scale fishing industry of Oman is responsible for almost 90 percent of the total marine fishery production. It is also the main supplier of fish for Omani households. This study analyzes the factors that determine small-scale fishermen’s income on Oman’s Batinah Coast, which has almost 30 percent of Oman’s population and more than one-third of the small-scale fishermen. We find that fishermen’s income here can be explained broadly under four major blocks of variables: geographical region, fishing inputs and catch, socioeconomic and demographic characteristics, and the nature of the relationship with fisheries extension services. In general, the Wilayat (local administrative units) failed to make any significant impact on fishermen’s income. The variable “Fishing inputs and catch,” such as increases in engine power, boat length, weekly catch, and number of weekly trips, positively impacted fishermen’s income while increases in weekly fishing costs, number of crew members, and difficulty in getting ice had a significantly negative effect on the income. Furthermore, socioeconomic and demographic characteristics also contributed significantly in determining the fishermen’s income level. The other important findings were related to extension services. The variables “Fishermen’s exchange of information and cooperation with the ministry” and “Fishermen’s involvement in the extension activities” were found to have positive effects on fishermen’s income levels. Capitalizing on these findings could improve fishermen’s incomes and their lives across the region, as well as nationally.

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The objectives of these Technical Guidelines are to provide a focus on small-scale fisheries and their current and potential role in contributing to poverty alleviation and food security by expanding on the guidance on small-scale fisheries offered by the Code. The Guidelines are complementary to existing Technical Guidelines for Responsible Fisheries. Most small-scale fishers are in developing countries and many live in communities characterized by poverty and food insecurity. Small-scale fishing communities are faced with an array of serious problems, including overexploitation and depletion of resources, lack of alternative sources of employment, rapid population growth, migration of populations, displacement in coastal areas due to industrial development and tourism, pollution and environmental degradation and conflicts with large commercial fishing operations. However, small-scale fisheries are critical for food security and poverty alleviation in many countries. The first part of the Guidelines discusses the current contribution, role and importance of small-scale fisheries in poverty alleviation and food security. It examines the importance of small-scale fisheries for poverty alleviation at a national, local and household level. It also notes the nutritional qualities of fish and thus the particular role of fish in nutritional aspects of food security. The fact that about half of all fish caught for human consumption comes from small-scale fisheries underlines the importance of this subsector for the world fish supply. In many countries small-scale fisheries contribute to national food security both directly – where fish is a crucial part of the daily diet, and indirectly – by generating foreign exchange earnings that enable the purchase through trade of a range of food products. The second part of the Guidelines explores ways through which the contribution of small-scale fisheries to poverty alleviation and food security could be enhanced. A vision for the future of small-scale fisheries is presented as a goal towards which the subsector should develop. Ensuring greater participation by small-scale fishers and their communities in the formulation of policies, the development of related legislation and regulations, and in management decision-making and implementation processes, is vital to the realization of this vision. The central role of effective fisheries management, the importance of considering cross sectoral uses of fisheries and related resources, the special role of women in fish marketing, processing and value addition, the significant scope for trade, the critical role that adequate financing may have in enabling transitions for effective fisheries management and the role of knowledge in making informed decisions are all discussed in these Guidelines. (PDF contains 97 pages)

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RRAs were carried out in two Small Tank Cascade systems (STCs) of North West Province, Sri Lanka (less than 1000 ha total watershed area). A total of 21 tanks and 7 villages were investigated with primary emphasis on two upper watershed communities. The two systems differ primarily in their resource base; namely rainfall, natural forests and proximity to large scale perennial irrigation resources. [PDF contains 86 pages]

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One of the major problems in the mass production of sugpo is how to obtain a constant supply of fry. Since ultimately it is the private sector which should produce the sugpo fry to fill the needs of the industry, the Barangay Hatchery Project under the Prawn Program of the Aquaculture Department of SEAFDEC has scaled down the hatchery technology from large tanks to a level which can be adopted by the private sector, especially in the villages, with a minimum of financial and technical inputs. This guide to small-scale hatchery operations is expected to generate more enthusiasm among fish farmers interested in venturing into sugpo culture.

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The annual catches of four small longliners operating off northeast Brazil from 1983 to 1997 were examined across different areas and locations. The total catch comprised tunas (30%), sharks (54%), billfishes (12%), and other fish species (4%). Fishing strategy and annual composition of catches showed large spatial and temporal variabilities with the dominant catches alternating among yellowfin tuna, Thunnus albacares; gray sharks, Carcharhinus spp.; and blue shark, Prionace glauca. Catches of blue and gray sharks showed a significant interaction among seamounts, with gray sharks occurring in maximum abundance around those seamounts that had relatively deep summits and low-sloping depth profiles. Results are discussed in terms of the various factors that may have influenced distribution of effort.

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Over the years, aquaculture has developed as one of the fastest growing food production sectors in Nepal. However, local fish supplies have been extremely inadequate to meet the ever increasing demand in the country. Nepal imports substantial quantities of fish and fish products from India, Bangladesh, Thailand, and elsewhere. Integration of pond aquaculture in existing crop-livestock-based farming system is believed to be effective in increasing local fish supply and diversifying livelihood options of a large number of small-holder farmers in southern plains (terai) and mid-hill valleys, thereby also increasing resilience of rural livelihoods. There is growing appreciation of the role of small-scale aquaculture in household food and nutrition security, income generation, and empowerment of women and marginalized communities. This book includes a total of 25 papers presented at the ‘Symposium on Small-scale Aquaculture for Increasing Resilience of Rural Livelihoods in Nepal’, held in Kathmandu on 5-6 February 2009. The papers cover technological, social, economic and environmental aspects of small-scale aquaculture development emerged from research and development initiatives of governmental, non-governmental and international research organizations in recent decad

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Turbulence and internal waves are probably important in generating layered structures in frontal region of marine environments (e.g. near river plumes outflow into the sea). Here we investigate the role of normal modes of internal waves in generation of layered structure in a part of Persian Gulf where river plume inters and in some laboratory experiments. The model prediction and observations show that layers so formed have a thickness of about 2m based on salinity variations with depth, but layers (about 5m) based on horizontal velocity profiles. Laboratory experiments with a plume outflow in a Filling Box profile also generate normal mode layered structure with 21H=0.5 (where A is layer thickness and H is the plume depth). In these experiments as Re of the flow is smaller than the Re of field flow. The normal modes are substantially dissipated with depth. Typical values of dissipation factor is about 0(100). This factor for field observation is 0(10) which is still substantial. Qualitative comparison between layered structure in field and laboratory is good. It should be emphasized that field observation is for semi-enclosed seas but the laboratory experiments are for enclosed region. Hence some of the discrepancies in the results of two cases are inevitable. Layered structures in marine environments are also produced by double diffusive convection. In this region this should be studied separately.