983 resultados para Agricultural ecology
Resumo:
Juvenile chinook salmon, Oncorhynchus tshawytscha, from natal streams in California’s Central Valley demonstrated little estuarine dependency but grew rapidly once in coastal waters. We collected juvenile chinook salmon at locations spanning the San Francisco Estuary from the western side of the freshwater delta—at the confluence of the Sacramento and San Joaquin Rivers—to the estuary exit at the Golden Gate and in the coastal waters of the Gulf of the Farallones. Juveniles spent about 40 d migrating through the estuary at an estimated rate of 1.6 km/d or faster during their migration season (May and June 1997) toward the ocean. Mean growth in length (0.18 mm/d) and weight (0.02 g/d) was insignificant in young chinook salmon while in the estuary, but estimated daily growth of 0.6 mm/d and 0.5 g/d in the ocean was rapid (P≤0.001). Condition (K factor) declined in the estuary, but improved markedly in ocean fish. Total body protein, total lipid, triacylglycerols (TAG), polar lipids, cholesterol, and nonesterified fatty acids concentrations did not change in juveniles in the estuary, but total lipid and TAG were depleted in ocean juveniles. As young chinook migrated from freshwater to the ocean, their prey changed progressively in importance from invertebrates to fish larvae. Once in coastal waters, juvenile salmon appear to employ a strategy of rapid growth at the expense of energy reserves to increase survival potential. In 1997, environmental conditions did not impede development: freshwater discharge was above average and water temperatures were only slightly elevated, within the species’ tolerance. Data suggest that chinook salmon from California’s Central Valley have evolved a strong ecological propensity for a ocean-type life history. But unlike populations in the Pacific Northwest, they show little estuarine dependency and proceed to the ocean to benefit from the upwelling-driven, biologically productive coastal waters.
Resumo:
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.
Resumo:
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.
Resumo:
In June, 1961, discussions were held in London to consider the future of the East Africa High Commission Services. It was agreed that the functions of the East Africa High Commission, with the exception of Defence, should be transfered to the East African Common Services Organization, which was subsequently established on 9th December, 1961, on the achievement of independence by Tanganyika. The Common Services Organization is controlled by an Authority, consisting of the principal elected Minister in each of the East African territories, which is responsible for the overall policy and direction of the Organization. The Authority is assisted by four Ministerial Committees, of which one is responsible for the Social and Research Services of the Organization
Resumo:
About 20% of Uganda territory is surface water from which 250,000m tons of fish is produced. In addition to fish exports which earned the country US$ 40m in 1996, fish provides 50% of protein diet of the 20m people translating into a per capita consumption of 12kg. It is estimated that fishery related activities employ at least one million people.The goal of FIRRI is to generate and transfer improved technologies and policy recommendations aimed at ensuring sustainable fish production and a healthy environment in which fish is produced.
Resumo:
Lake Victoria shoreline in Jinja Municipality has four urban wetlands of Kirinya West/Loco, Kirinya East/Walukuba, Masese and Budumbuli which have undergone major changes during the past fifty years due to increased human activities. Amongst these activities is the continuous inflow of agricultural run-off, industrial and municipal wastewater. A significant increase in nutrient loads of Nitrogen and Phosphorus from the catchment area continues to enhance eutrophication of Lake Victoria. Pollution from point sources (Industrial plants and NWSC Kirinya final maturation pond) into Jinja’s urban wetlands were therefore studied using a simplified material flux analysis methodology to identify the active elements and estimate the pollution loads due to Nitrogen, Phosphorus, Carbon (nutrients), Chromium, Copper, Lead, Nickel and Manganese metals.
Resumo:
It is now clear that fisheries resources are among the key assets contributing to the national development objective of poverty eradication through providing food, employment, income and export earnings. It was recently reported in the papers that monthly fish exports had increased by 23% and fetched about US$ 10 Million during the month of November 2001 alone. This value may be underestimated as it is based solely on recorded exports from fish processing factories numbering 12. Although fisheries resources are renewable they can be depleted through unsustainable exploitation. It is therefore important to ensure that there is guided development and management of this asset so that it can continue contributing to the livelihood of the people who depend on it. Therefore, FIRRI contributes to the fisheries sub-sector developmental objective of ensuring increased and sustainable fishery production and utilization by providing information to guide sustainable management of capture fisheries resources and development of aquaculture.
Resumo:
Fisheries continue to be important in the national economy, especially as an export commodity. Fish exports increased from 15,876 tonnes valued at 34.4 million US$ in 2000 to 28,153 tonnes valued at 79.0 million US$ in 2001. Consequently information for sustainable exploitation and management of fish stocks is a priority. In order to fulfill this requirement, FIRRI has been implementing two research projects. The first project focuses on sustaining and increasing capture fisheries production through management of fish stocks, biodiversity and environment of aquatic systems. The second project focuses on increasing fish production through improved fry production and pond management and feeding of cultured species.
Resumo:
One of the avenues through which the Government objective of poverty eradication in Uganda can be achieved is Fisheries development and management. Up to 20% of Uganda’s surface area is covered by aquatic systems i.e. lakes, rivers, streams and swamps and to a large extent, all these are interconnected. The large lakes: Victoria, Albert, Kyoga, George and Edward are sites of the more important commercial fisheries, but even the smaller water bodies, rivers (e.g. the Rivers Nile and Kagera) and the surrounding swamps provide sources of livelihood to rural areas. Fish is an important source of high quality food, employment revenue and is currently the second most important export commodity next to coffee generating approximately US $ 80 million annually. Fish exports to regional markets are worth at least US $ 20 million annually. Fish flesh is rich in proteins, which are superior to those of beef and poultry. Fish flesh contains an anticholesterol which assists in reducing heart diseases. Some fishes are of medicinal value e.g. haplochromines (Nkejje) are used to treat measles. Most of the fish in Uganda is got from lakes Victoria, Kyoga, Albert and Albert Nile, Edward and George production systems as well as from the 160 minor lakes and rivers and the associated wetland systems. Capture fisheries based in these systems contribute up to 99% of the fish production in Uganda but aquaculture is also picking up. The fishing industry employs up to one million Ugandans
Resumo:
About 18% of Uganda’s surface area is covered with water from which 300,000 metric tonnes of fish are produced. Fish are currently the second most important export commodity generating approximately US$100 million. Fish provides 50% of protein diet for the 20 million people translating into per capita consumption of 12 kg. Close to the production system, this figure rises to 50 – 100 kg. It is estimated that fishery-related activities employ at least one million people countrywide (i.e. 5% of the population). Fish is an important source of high quality food, employment, and revenue and it is currently the second most important export commodity next to coffee generating approximately US $ 80 million annually. Fish exports to regional markets are worth at least US $ 20 million annually. Fish flesh is rich in proteins, which are superior to those of beef and poultry. Fish flesh contains an anticholesterol which assists in reducing heart diseases. Some fishes are of medicinal value e.g. haplochromines (Nkejje) are used to treat measles. Most of the fish in Uganda is got from lakes Victoria, Kyoga, Albert and Albert Nile, Edward and George production systems as well as from the 160 minor lakes and rivers and the associated wetland systems. Capture fisheries based in these systems contribute up to 99% of the fish production in Uganda but aquaculture is also picking up. The fishing industry employs up to one million Ugandans.
Resumo:
About 18% of Uganda’s surface area is covered with water from which about 300,000 metric tonnes of fish are produced. Fish are currently the second most important export commodity generating approximately US$100 million annually. Fish provides 50% of protein diet for the 20 million people translating into per capita consumption of 12 kg. Close to the production system, this figure rises to 50 – 100 kg. It is estimated that fishery-related activities employ at least one million people countrywide (i.e. 5% of the population). Fish exports to regional markets are worth at least US $ 20 million annually. Fish flesh contains an anticholesterol which assists in reducing heart diseases. Some fishes are of medicinal value e.g. haplochromines (Nkejje) are used to treat measles. Most of the fish in Uganda is got from lakes Victoria, Kyoga, Albert and Albert Nile, Edward and George production systems as well as from the 160 minor lakes and rivers and the associated wetland systems. Capture fisheries based in these systems contribute up to 99% of the fish production in Uganda but aquaculture is also picking up. The fishing industry employs up to one million Ugandans