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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 17 (1986), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. The movement pattern and the abundance of perch, Perca fluviatilis L., were studied in the Kleine Nete, a eutrophic, canalized lowland river in north Belgium. Since the behaviour of perch is strongly affected by habitat type, two kinds of river section were chosen, based on physical characteristics: homogeneous sections with regard to depth, bottom type and current speed; and heterogeneous sections with a riffle and pool pattern. The fish were caught by electrofishing and all perch larger than 10 cm were marked individually. The population densities were much higher in the heterogeneous parts. In these sections about 30% of marked perch stayed within a home range, while in the homogeneous sections all were mobile. The older individuals showed a stronger tendency to accept a home range than the 1- or 2-year-old perch. This difference may be explained by different behaviour: young perch live in small schools, while older perch are often solitary. The low densities and the high mobility of perch in the homogeneous river sections indicate that these parts of the river are not a suitable habitat for perch. Habitat improvement of the homogeneous sections wilt probably result in higher overall population densities.
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  • 2
    ISSN: 1573-5117
    Keywords: water pollution ; Lake Tanganyika ; Burundi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sources of pollution at the north end of Lake Tanganyika are concentrated around Bujumbura, Burundi. The impact of River Ntahangwa on the water quality of this part of Lake Tanganyika was compared with that of an unpolluted river, the Mugere. A shallow bay, not influenced by a river, was used as a reference station. Chemical analyses were carried out at four week intervals during nearly a year. Samples were taken at different distances from the shore and at different depths. River impact was detected up to 100 m from both river mouths. Even at 50 m from the mouth of the polluted River Ntahangwa, no important decrease of dissolved oxygen was detected. Chlorophyll-a maxima were found 100 m from the Ntahangwa mouth, but this was also the case 100 m from shore in the unpolluted bay. Lake water at 60 m depth was saturated with oxygen during the dry season, as it used to be in 1956. The rivers studied descent initially within the lake due to greater sediment load and lower water temperature. Nevertheless, it appears that these rivers mix completely in the lake within 100–300 m from the river mouths. The direct effects from organic pollution of the Ntahangwa on the lake seem to be rather negligible. Appropriate anti-erosion measures should reduce massive sediment discharge into the lake.
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  • 3
    ISSN: 1573-5117
    Keywords: Lake Tanganyika ; weathering ; water chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The chemical composition of water in 13 small rivers of the north-western part of Lake Tanganyika was studied over a 15-month period. The factors influencing the water chemistry were studied by cluster analysis. On the basis of major ion concentrations three groups of rivers could be identified. Ionic differences between the groups depended on source altitude which was strongly related to pH, water temperature, conductivity, nutrient content and weathering intensity of dolomite – and pyrite-containing bedrock. These results are in agreement with the riverine inputs of nitrogen to Lake Tanganyika calculated by Hecky et al. (1991), but are ca. 30% lower than their estimated inputs of phosphorus and silicon.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 407 (1999), S. 65-73 
    ISSN: 1573-5117
    Keywords: Lake Tanganyika ; Burundi ; hydrodynamics ; sedimentation ; Rusizi River
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The inflow of River Rusizi to Lake Tanganyika has been assumed not to mix with the lake epilimnion as it would sink as an interflow or an underflow, because of its higher density due to sediment load, lower temperature and higher salinity. Nevertheless, efforts made to trace the Rusizi flow into the lake have failed. Ten sampling surveys were carried out from March 1994 to July 1995. Each consisted of 22 samples, at different distances off the Rusizi estuary and at different depths. Eighteen physical and chemical variables were studied at each site. The Rusizi water was always denser (800 – 1400 g m-3) than the lake water. The relative importance of temperature, suspended solids and salinity varied seasonally. A descent of the Rusizi inflow was observed. Close to the river estuary, river and lake waters mixed and Rusizi sediments settled. Complete mixing occurred within 800 m off- shore. The Rusizi inflow merged with the epilimnion rather than the hypolimnion. Horizontal spread by shorebound currents seemed to be more important than offshore spread.
    Type of Medium: Electronic Resource
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  • 5
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