981 resultados para Huanghe River Estuary


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Churchtown Weir in the River Wyre, North West of England, UK. This photo is part of a Photo Album that includes pictures from 1935 to 1954.

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This is the Wetland resource evaluation and the NRA's role in its conservation: Resource assessment report produced by North West Water in 1982. In this report data from a variety of sources in river Leven and Leven estuary have been examined to determine if there was any objective foundation for the allegations and for the assertion that poor fish catches were related to discharges of industrial effluent to the estuary. Catches of salmon and sea trout from the Leven did not appear to have suffered any long term declines and year to year fluctuations did not appear to be any more extreme than in other North West rivers. Fish surveys did not show any marked differences in the diversity or distribution of fish between the Kent and Leven estuaries but catches of flounders were consistently lower from the Leven estuary. Analysis of fisheries statistics of landings of fish and shellfish from Morecambe Bay did not show any evidence of localised declines in catches from the Leven estuary. Results of laboratory experiments suggested that populations of bivalve molluscs might be more at risk from the effects of discharges to the Leven estuary than resident or migratory fish.

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This is the report on the strategic fisheries stock assessment survey of the River Winster 1995 together with a coarse fish survey in 1994 and reference to the 1995 drought, produced by the Environment Agency North West in 1996. Salmonid production within the Winster catchment was dominated by trout although good densities of salmon juveniles were found on some main river sites. Despite suffering drought conditions for much of 1995, only salmon fry production appeared to have been affected. Coarse fish populations once found in the lower reaches of the Winster appear to have declined to very low levels with no fish sampled. This may be partly due to broken tidal gates allowing saline intrusion. It seems that the lower river was suited to the development of a recreational coarse fishery, now that the gates have been repaired. This report completes the strategic stock assessment surveys planned for the period 1992-1995. It represents the last major catchment that was surveyed to determine the current status of fisheries in the South and South West Cumbria areas.

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This is the report on the River Ehen salmonid fishery - current status and a summary of fisheries work during the period 1993-1996, produced by the Environment Agency North West in 1997. This report draws together a number of investigations and surveys undertaken following the 1993 Strategic fisheries survey of the River Ehen. It specifically details the historic catch data available for this catchment for both salmon and sea trout and examines the current stock levels based on this data. Concerns over sea trout stock levels are raised and a detailed examination of the possible limiting factors involved is included. Information from surveys on the River Keekle is analysed with reference to its potential for sea trout production both currently and with the proposed clean up on Oatlands tip. Salmon production in the historically acidified River Liza sub catchment is examined along with ways of boosting production further following recent reductions in acidic episodes. Future and current issues and actions required in the catchment are listed along with the responsible party and estimated costs involved.

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This is the Brown trout habitat assessment on the River Bela catchment produced by the Environment Agency North West in 1997. The Environment Agency (EA) and its predecessor the National Rivers Authority undertook strategic fish stock assessments in 1992 and 1995 on the River Bela catchment. These surveys found low numbers of brown trout {Salmo trutta) at some sites. Following this, habitat evaluation assessments were undertaken on the eleven poorest sites Factors probably responsible for declining trout populations on the three main tributaries of the Bela catchment include: Overgrazing by farm stock; Lack of suitable cover for parr; the absence of suitable spawning areas; existing potential of certain areas within the catchment not being utilised, due to poor dispersal. Habitat Improvement Schemes (H.I.S) are discussed and prioritised.

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This is the River Leith fluvial audit: Final project report produced by Lancaster University in 1998. Freeze cores extracted from the upper and lower ends of River Leith illustrate that the bed is highly compacted in the downstream reach. Fine material is locally derived from bedrock at depths of only 32 cms into the bed and in one core fine material is 66% of the extracted core. Levels of fines that are believed to be detrimental to fish are put at 20 to 30%. Reduced flow and stream power from water abstraction may lead to a greater infiltration of fine material if gravels are not regularly flushed through with flood flows. Infiltration of fine material can lead to river bed compaction and concretion. A small abstraction may have no effect on the morphology of a river if the reduced discharge is within the normal range of flows experienced. However if the impact on flows is small it is still possible that fine sediment problems will develop progressively and the effects may not be noticed for several years.