89 resultados para Green movement--Canada.


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Polyculture, as presently practiced in Nigeria, focuses interest mainly on finfish. This practice, apart from neglecting indigenous valuable species such as clams and water snails, does not make full use of existing biomass. This paper suggests possible deviations from normal practice. Inclusion of macroinvertebrates in a polyculture system and stocking, temporary bodies of water with seasonal species such as the fresh water crayfish are suggested. A final suggestion is to develop a polyculture of swamp rice and crayfish

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The aim of this study was to examine areas in which fishermen cooperatives can become involved and then suggest operational guidelines in order to increase fishermen income and also to make the Green Revolution Programme a success through increased production of fish. The paper enumerated different areas in which fishermen cooperatives can participate. These include: thrift and credits, thrift and savings, consumers and building cooperative societies. It is the belief of the author that the expansion of fishermen cooperatives into the areas mentioned in this paper can enable members to process and market their products more economically, buy supplies and equipment in large quantities and obtain lower cost credit

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(pdf contains 32 pages)

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A discussion is presented on the potential for fishery development in the Niger Delta region, considering engineering activities and food production potentials of the freshwater zone and immediate hinterland, the brackishwater mangrove swamps and the estuaries. An examination of current trends in the environment indicates that a possible solution to improved exploitation of the region lies in hydraulic engineering, the manipulation of environmental conditions through varying freshwater and seawater inputs so as to increase aquatic and wetland productivity

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ENGLISH: The growth of northern bluefin tuna is described by a two-stanza model. For fish between 191 and 564 mm in length the Gompertz curve, with values of 581 mm and 4.32 for Loo and K (annual), respectively, is used. The fish between 564 and 1530 mm grow linearly, at the rate of 0.709 mm per day. Age-O fish tagged and released in the western Pacific Ocean have been recaptured in the western, central, and eastern Pacific. The minimum time between release in the western Pacific and recapture in the eastern Pacific is 215 days. Older fish, mostly Land 2-year olds, tagged and released in the eastern Pacific have been recaptured in the eastern and western Pacific. The minimum time between release in eastern Pacific and recapture in the western Pacific is 674 days. The coefficient of natural mortality is estimated from data on growth and ambient temperature to be 0.276 on an annual basis, with 90-percent confidence limits of 0.161 and 0.47L Spawning of northern bluefin takes place only in the western Pacific. Some of the juveniles migrate to the eastern Pacific, where they reside for several months to several years before returning to the western Pacific. The portion of fish which migrate to the eastern Pacific varies among years, and this appears to be an important cause of the annual variation in the catches in the eastern Pacific Ocean. SPANISH: El crecimiento del atún aleta azul del norte es descrito por un modelo de dos estadios. Para los peces de entre 191 y 564 mm de talla se usa la curva de Gompertz, con valores de 581 mm y 4.32 para Loo y K (anual), respectivamente. Los peces de entre 564 y 1530 mm crecen de forma lineal, a 0.709 mm por día. Peces de edad Omarcados y liberados en el Pacífico occidental han sido recapturados en el Pacífico occidental, central, y oriental. La demora mínima entre la liberación en el Pacífico occidental y la recaptura en el Pacífico oriental es de 215 días. Peces mayores, principalmente de 1 ó 2 años de edad, marcados y liberados en el Pacífico oriental han sido re capturados en el Pacífico occidental y oriental. La demora mínima entre la liberación en el Pacífico oriental y la recaptura en el Pacífico occidental es de 674 días. Se estima el coeficiente de mortalidad natural a partir de los datos de crecimiento y temperatura ambiental en un 0.276 anual, con límites de confianza al 90% de 0.161 y 0.471. El aleta azul del norte desova únicamente en el Pacífico occidental. Algunos de los juveniles migran al Pacífico oriental, donde permanecen entre varios meses y varios años antes de regresar al Pacífico occidental. La porción de los peces que migran al Pacífico oriental varía entre años, y ésto parece ser una causa importante de la variación anual en las capturas en el Océano Pacífico oriental. (PDF contains 94 pages.)

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Blue-green algae (cyanobacteria) have had a profound and unparalled impact on the aquatic environment because of the phenomenon of bloom formation. In many countries, water management is threatened with extensive and persistent noxious blooms of blue-green algae in surface and near-surface mesotrophic and eutrophic waters. In view of this, ecological and physiological factors responsible for blue-green algal dominance are discussed. The implications of cyanobacterial blooms are highlighted and recommendations made to combat this menace

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The incidence of blue-green algal blooms and surface scum-formation are certainly not new phenomena. Many British and European authors have been faithfully describing the unmistakable symptoms of blue-green algal scums for over 800 years. There is no disputing that blue-green algal toxins are extremely harmful. Three quite separate categories of compound have been separated: neurotoxins; hepatotoxins and lipopolysaccharides. There is a popular association between blue-green algae and eutrophication. Certainly the main nuisance species - of Microcystis, Anabaena and Aphanizomenon are rare in oligotrophic lakes and reservoirs. Several approaches have been proposed for the control of blue-green algae. Distinction is made between methods for discharging algae already present (eg algicides; straw bales; viruses; parasitic fungi and herbivorous ciliates), and methods for averting an anticipated abundance in the future (phosphorous control, artificial circulation etc).

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Many have observed the reduction of the quantity of zooplankton in the presence of water blooms. It is known that in seas zooplankton as it were avoids places of accumulation of blue-green algae. By observations on one of the tributaries of the Rybinsk reservoir - the River Shumorovka - the authors tried by simultaneous collections to trace the changes in numbers, not only of zoo- and phytoplankton but also of bacteria. The plankton was collected by quantitative nets with suitable numbers of gauze and bacteria were taken account of by the method of direct calculation on membrane filters. It can be seen that the development of blue-green algae appears as an important factor, determining not only the intensity but also the direction of the process of production of zooplankton.

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Viruses, which are characterised by a relative simplicity of chemical composition, are involved with all the groups of the animal and plant world. The discovery of viruses of lower organisms has special interest. Along with the already known viruses lysing bacteria and actinomycetes, viruses have been discovered in recent years which lyse algae. During investigations of water from water-bloom patches and of mud taken from zones of massive accumulation of blue-green algae in the Dneprovsk reservoirs, the authors obtained viruses lysing algae. The revealing of viruses producing lysis of blue-green algae, which one could use in the control of water-blooms, has the greatest interest. With this aim, samples of water were collected from various zones of water-bloom patches in the Kremenchug, Dneprovsk and Kukhov reservoirs. For viruses lysing algae we propose the name 'algophages'. Along with the existence of viruses of algae of the phage type, one cannot deny the possibility of the existence of viruses of another type, multiplying in the cells of algae and causing their virus illnesses.

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For many years a dye has been used in the practise of pisciculture and pond management, which is known by the name of malachite green, and is used to combat fungus on fish, fish eggs and external animal parasites on fish. The authors describe the problem of the application of malachite green in pisciculture and undertake special, complementary research.

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Science Cafes present a casual meeting place where people who may have little or no science background can learn about a current scientific topic in an informal and friendly environment. The coffee shop setting is designed to be inviting and informal so that students, faculty, and community members can feel comfortable and engage in lively and meaningful conversations. The café is organized around an interesting scientific topic with a brief presentation by a scientist and may include a short video clip. A Science Café can (1) provide an opportunity and venue for increasing science literacy, (2) publicize local scientific endeavors, and (3) identify the library as an epicenter of informal education on the campus and in the community. This presentation will describe the development of the Science Café at the University of Southern Mississippi Gulf Coast campus Library in Long Beach and plans for future cafes on the Mississippi coast.

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Cow Green is a new reservoir situated in Pennine moorland. It has an area of 312 ha, a capacity of 40 . 9 x 10 SUP-6 m SUP-3 and a maximum depth of 22 . 8 m. The function of the reservoir is to regulate flow in the River Tees to provide industrial Teesside with sufficient water during the dry spells. Invertebrate studies were carried out in the Tees to monitor changes resulting from the construction of the reservoir both in the flooded basin and below the dam. The overall effect of the reservoir on the Tees has been to increase the numbers and biomass of certain taxa, but generally not at the expense of previous fauna. Some of the positive effects, ie. increase in number and biomass, and maintenance of faunal diversity, may in part be attributable to the presence of the rapids and waterfall. Turbulence resulting from this rapid flow over heterogeneous bottom is sufficient to prevent clogging of interstitial spaces by silt and to maintain the variety of ecological niches necessary for a diverse fauna.

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Post impoundment observations on the fish populations of the River Tees, downstream from the Cow Green Reservoir were made between 1971 and 1980. Both bullhead (Cottus gobio L.) and brown trout (Salmo trutta L.) population densities increased in the river after impoundment but changes in growth rate were small. Investigations into the stomach contents of the two species reflects the results of other work on increases of benthos in the river. Following regulation there was an increase in the quantity of Ephemerella ignita found in trout stomachs while in the bullhead, regulation caused an increase in the importance of Mollusca and a decrease in importance of Ephemeroptera and Plecoptera.

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A number of authors have described the manner in which young salmonids, soon after emergence from the gravel, set up and defend territories. This leads to mortality or downstream displacement of the individuals which are unable to acquire territories and is widely accepted as the main method of population regulation amongst young salmonids. In some field experiments the fish were constrained in screened reaches and the option of downstream dispersal for the surplus fry was thus excluded. In order to explore some aspects of downstream dispersal more closely under conditions which gave more control than is obtained in a natural stream, four experimental channels were set up at Grassholme reservoir in Teesdale. The report describes the results of investigations on the timing and rate of downstream movement of young brown trout (Salmo trutta L.) and Atlantic salmon (Salmo salar L.) out of experimental channels, with special reference to the effect of water velocity on the rate of ”emigration”.

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The word ”Broads” is used to describe a series of relatively shallow lakes resulting from the flooding of medieval peat diggings. Broadland is essentially freshwater, but because the rivers have such low gradients the lower reaches are brackish. The influence of tide is particularly apparent on the River Yare; in Norwich 40 km from the sea there is a vertical movement of half a metre at spring tide. This study examines the problems that the broadlands are facing. The problems are basically the progressive loss of aquatic plants, in particular the macro- phytes, animal life, outbreaks of avian botulism, occasional fish kills due to a toxin produced by the blue-green alga Prymesium parvum and the emergence of very heavy algal blooms. The main factor for the deteriation of the Broaslands is the eutrophication resulting from enhanced nutrient inputs, in particular of nitrates and phosphates, from a variety of sources. The most important of these are sewage effluents, agricultural drainage, which includes fertilisers and nutrient rich effluents from piggeries and dairy un