980 resultados para Aquatic ecology.


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Cambodia’s recent freshwater fishery sector reform, instigated at the top level of government, is one of the country’s most significant contemporary policy developments addressing natural resources management and rural development. Implemented in two main waves, the reforms culminated in the complete removal of inland commercial fishing lots. Yet serious problems still need to be addressed, including reportedly widespread illegal fishing, difficulties in protecting critical habitats, and competition among state agencies over resource management authority. This report summarizes the context of the recent fishery reforms, analyzes challenges and opportunities for policy implementation after the reforms, and details the outcomes of local institutional innovations in Kampong Thom Province, followed by a discussion of the implications for ongoing efforts aimed at reducing resource conflict and building livelihood resilience.

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Lake Victoria fisheries face severe environmental stresses. Stocks are declining in a context of increasing population and growing demand for the lake’s resources. Rising competition between users is putting conservation goals and rural livelihoods at risk. While Uganda’s co-management policy framework is well-developed, key resources for implementation are lacking, enforcement is poor, and the relations between stakeholders are unequal. Poor rural resource users face significant challenges to effectively participate in fisheries decision-making. This case study demonstrates the progress that can be made using a collaborative approach to catalyze community-led actions linking public health, sanitation and environmental conservation in difficult circumstances, even over a relatively short time period. Multistakeholder dialogue can bring to light the sources of conflict, pinpoint governance challenges, and identify opportunities for institutional collaboration to address community needs. At the same time, the process can help build trust, confidence in collective action and public accountability.

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This paper embodies details and method of operation of a mechanical device developed for eradication of submerged aquatic weeds. The economics of operation is also discussed.

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An experiment was conducted in brackish water ponds with transplanted aquatic weed (Najas sp.) to study the effect of submerged aquatic vegetation on culture of Penaeus monodon. Out of six ponds three were without any aquatic vegetation (T1) while in other three ponds weeds were planted covering 40% of the pond bottom (T2). Hatchery produced post larva of P. monodon (0.006 g) were stocked in all ponds at a density of 40,000/ha. Shrimps were fed twice daily with commercial and formulated feed prepared from locally available ingredients. After 105 days of rearing shrimp of highest average weight (63.18g) was obtained from T2 with a survival rate of 25.90% and the total production was obtained at 654.54 kg/ha. The average weight, survival and total production of shrimp in T1 were 35.0 g, 28.76% and 405.63 kg/ha, respectively.

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Weimin, ZOU, lexian YANG, lan JIANG, Shuqin WU, Qi YI, Jianli WU

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Aquatic insects are relatively common at artificial lights and are often taken in light traps operated for catching other insects. They are however seldom recorded. These records are however of importance in understanding their distribution and abundance. Aquatic Coleoptera and Hemiptera are of importance in fisheries because some of them are predators on small fish whilst others serve as food for fishes of all sizes. Some like the Corixidae are of special interest because they can utilize the bottom ooze which is abundant especially in small habitats. Fernando (1961a) gave a comprehensive bibliography of records at light. In the present paper a number of records are given from various parts of Asia, where in the past records were very few. They are based on collections made by the author and also on material in the Zoological Survey of India, Calcutta. Amongst specimens sent for study by the Bernice P. Bishop Museum, Honolulu, were a few specimens which had been recorded at light.

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The Annual report covers Research work of the Organization carried out during the period 1975. Its explains the following research work: Haplochromis Studies, Electrophoresis,The Ecology of Haplochromis in the northern waters of Lake Victoria Limnology, Aquatic Pollution and Biochemical Studies The Biology of Synodontis in Lake Victoria Riverine Fisheries, Inshore Fishery of the Kenyan-Waters of Lake Victoria Biostatistics, the Inshore Fisheries of the Western part of Lake Victoria, The Offshore Fisheries of Kenyan Waters of Lake Victoria Lake Mobutu Sese Seko: Stock Assessment and Ecological Studies Fishery Economics, The Biology of Bagrus docmac in Lake Victoria Fishery Resource Surveys of Lake Wamala and Kijanebalola

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Six species of spiny lobsters of the genus Panulirus have been recorded in Ceylon waters. It is clear, therefore, that species dominance and ecological separation in the genus Panulirus is demonstrable and that the separation is dependent on the particular ecological preferences of the different species. In order to determine the factors governing the ecological separation, it was decided to make a detailed study of the environments in which the different species were found. Diving operations constituted the chief method of investigation. However, information was also obtained from commercial skin-divers, trap fishermen, bottom-set net fishermen and trawling operations. The period of investigations extended from 1962-1968.

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The Austrian-Ceylonese hydrobiological mission studied 38 biotopes; 28 of which contain Odonata. From the Zygoptera the Calopterydoidea seem to be the dominant form (22 habitats), while the Coenagrionoidea are scarcer (11 habitats). The most frequent species was Euphaea splendens (Epallagidae - 16 habitats) followed by Vestolis apicalis nigrescens (Calopterygidae, 8 habitats) and Neurobasis chinensis (Calopterygidae, 6 habitats). From the Anisoptera Zygonyx ceylanica (Libellulidae: Zygonictinae) was the dominant form (8 habitats), but some Libellulinae remain undescribed. The number of species varied greatly between different biotopes. The biotopes containing Odonata are small brooks, in which the pH was mostly on the limit between acid and alkaline reaction. They are fast running waters, situated in most cases on lower or middle elevations, only three species being found in higher elevations (1800-2000 m). Adaptations to fast currents and other factors are described.

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Although other research studies on areas such as the physical-chemical, nutrients and phytoplankton status of Lake Kyoga systems have been given a lot of attention (e.g. Mungoma 1988 and NaFIRRI 2006), efforts to determine the pollution status of this system, especially by heavy metals as one of the worldwide emerging environmental problems, is still limited. Many trace metals are regarded as serious pollutants of aquatic ecosystems because of their persistence, toxicity and ability to be incorporated into food chains (Mwamburi J., and Nathan O.F., 1997). Given the rapid human population growth and the associated economic activities both within the rural and urban areas in Uganda, such fish production systems are becoming very prone to various kinds of pollution including that by heavy metals. Anthropogenic factors such deforestation, use of chemicals and dumping of metallic products, spillages of fuels from outboard engines and many others and or natural processes involving atmospheric deposition by wind or rain, surface run-offs and streams flows from the catchment introduces heavy metals into the lake environment,.