976 resultados para pelagic fish
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This is the Effect of water quality on coarse fish productivity and movement in the Lower River Irwell and Upper Manchester Ship Canal: a watercourse recovering from historical pollution report produced by the Environment Agency in 2003. The aim of this study was to investigate the impact of water quality upon coarse fish population dynamics in a lowland, urban watercourse. All of the research carried was undertaken in the lower River Irwell and upper Manchester Ship Canal, between February 1998 and December 2001. Of particular interest was the natural sustainability of the urban fishery given recent concern raised in the angling community over an apparent decline in coarse fish populations in lowland rivers. The research described in this report has concentrated upon the role of water quality in determining coarse fish population dynamics, and in particular: The impact of water quality upon fish growth and productivity; The impact of poor water quality and low dissolved oxygen concentrations upon fish distribution and movement; The impact of water quality upon the sexual development of fish.
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This is the report on the Effect of Abstraction on Fish and Fisheries presented at the 24th IFM Annual Study Course, The Changing Face of Fisheries September 1993 at Cardiff. Water is abstracted from rivers for a wide variety of uses and causing potential for conflicts between abstracters, fisheries and conservation interests, especially during natural low flows. It looks at the potential effects that flow reduction has over various stages of salmonids at various stages of their life history. The flow at the time of smolt migration has been found to be positively correlated with the number of returning adults, and flow is considered to be one of the most important environmental factors inducing salmonids to enter fresh water and ascend rivers. The importance of time series data on fish stocks and angling success together with models which ultimately relate discharge to standing stock are discussed in relation to the setting up of Minimum Acceptable Flows.
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This is the episodic variations in stream water chemistry associated with acid rainfall and run-off and the effect on aquatic ecosystems, with particular reference to fish populations in North West England produced by the North West Water Authority in 1985. This report looks at the biological, physical and chemical information collected over a five year period from over 100 sites on upland streams in the North West Region of which drained rocks of low buffering capacity. In both Lake District and South Pennine sites striking differences were found between the composition of invertebrate communities inhabiting acid-stressed and less acid-stressed streams. Electric fishing surveys showed that acidic streams (geometric mean pH <5.5) generally had abnormally low densities of salmonids ( < 0 .2m2) and that 0+ fish were very few or absent. The latter indicates recruitment failure. Salmon were more sensitive than trout to low pH.
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This is a comparative survey of the Fish Populations of 10 West-Midlands Mere of Site of Special Scientific Interest Status. The meres of the Shropshire-Cheshire plain (West Midlands) comprise over 60 water bodies. Water quality in the meres ranges from naturally eutrophic to nutrient limited and some of them have received Site of Special Scientific Interest status (SSSIs). This survey was commissioned in order to obtain quantitative information on the fish fauna of selected SSSIs and evaluate the likely impact of fish on other species within the community. The current survey was concerned with 10 of the West Midlands’ meres, a cross section of sites was selected. Sites were widely distributed from Marton Pool in the south-western part of Shropshire to Tabley moat in Chesire. Meres varied in size, depth and nutrient status. All were to be sampled using the methods outlined. The report is divided into different sections for clarity and ease of reference. The materials and methods section provides an outline of the location and status of each mere and information on known fish species present. The results were considered individually and comparatively, relative abundance of fish, species present, their diet, sex, age, parasite burdens and growth. Inter-site comparisons were made using information derived from echo-soundings, growth rate, diet, and species abundance for each site. The final section will be in the form of a general discussion, comparative information from longer term studies, conclusions and recommendations.
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Two men working in a weir and fish pass at Whitendale, North West England, UK. This photo is part of a Photo Album that includes pictures from 1935 to 1954.
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Rooks fish pass at Garstang Weir in the River Wyre, North West England, UK. This photo shows pollution in River Lune in July 1949. This photo is part of a Photo Album that includes pictures from 1935 to 1954.
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Two men working in a weir and fish pass at Whitendale, North West England, UK. This photo is part of a Photo Album that includes pictures from 1935 to 1954.
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Photo of a check trap in Abbeystead Fish Pass in the River Wyre in 1949. The River Wyre is located in the North West of England, UK. This photo is part of a Photo Album that includes pictures from 1935 to 1954.
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River Clough Farfield Weir showing a gap made for migratory fish in June 1949 (Lune). This photo is part of a Photo Album that includes pictures from 1935 to 1954. This Album was held by the EA North West.
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Fish trap at Garstang weir in the River Wyre, North West of England, UK. This photo shows pollution in River Lune in July 1949. 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 Fish communities in rivers to be affected by Roadford Reservoir report produced by South West Water Authority in 1978. Surveys were carried, out on the Rivers Wolf, Thrushel, Lew and Lumburn, which are likely to be affected directly and indirectly by the construction and use of Roadford Reservoir. Of the upper reaches of three rivers to be affected directly by water releases, two were found to support abundant stocks of salmon and trout, and the third was found to contain abundant stocks of trout and eels. The River Thrushel will be affected indirectly and in this river salmon and trout stocks were present in slightly lower abundance than in others. Population estimates, densities, mean lengths and approximate biomass values were calculated. Other species were present in all rivers, usually in great abundance.
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To ensure the authentication of fishery products lacking biological characters, rapid species identification methods are required. Two DNA- and protein-based methods, PCR-SSCP (polymerase chain reaction - single strand conformation polymorphism) of a 464 bp segment of the cytochrome b – gene and isoelectric focusing (IEF) of water-soluble proteins from fish fillets, were applied to identify fillets of (sub-) tropical fish species available on the European market. Among the samples analysed were two taxonomically identified species from the family Sciaenidae and one from Sphyraenidae. By comparison of DNA- and protein patterns of different samples, information about intra-species variability of patterns, and homogeneity of batches (e.g. fillet blocks or bags) can be obtained. PCR-SSCP and IEF may be useful for pre-checking of a large number of samples by food control laboratories. Zusammenfassung Zur Sicherstellung der Authentizität von Fischerei-Erzeugnissen ohne biologische Merkmale sind schnelle Verfahren zur Speziesidentifizierung hilfreich. Zwei Methoden der DNA- bzw. Protein-Analyse wurden eingesetzt, um Filets (sub-) tropischer Fischarten, die auf dem europäischen Markt angeboten werden, zu identifizieren. Bei diesen Methoden handelt es sich um die PCR-SSCP (Polymerase-Kettenreaktion – Einzelstrang-Konformationspolymorphismus) – Analyse der PCR-Produkte und die IEF (isoelektrische Fokussierung) der wasserlöslichen Fischmuskelproteine. Unter den untersuchten Proben waren zwei taxonomisch bestimmte Arten aus der Familie Sciaenidae und eine Spezies aus der Familie Sphyraenidae. Durch Vergleich der DNA- bzw. Proteinmuster lassen sich Informationen über die intra-spezifische Variabilität solcher Muster und die Einheitlichkeit von Partien (beispielsweise Filetblöcke oder Filetbeutel) gewinnen. PCR-SSCP und IEF können in Laboratorien der Lebensmittelüberwachung als Vortest gerade bei hohen Probenzahlen sinnvoll eingesetzt werden.
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Egypt’s aquaculture production (921,585 tonnes in 2010) is by far the largest of any African country. The aquaculture sector, dominated by semi-intensive pond production of tilapia, makes a significant contribution to income, employment creation and food and nutrition security in the country, all of which are national priority areas given low per capita income levels, rising population, worsening food and nutrition security indicators, and official unemployment levels which have remained at around 10% for the last ten years. The Improving Employment and Income through Development of Egypt’s Aquaculture Sector (IEIDEAS) project funded by the Swiss Agency for Development and Cooperation (SDC) is a three-year project which commenced in December 2011, and which aims to support the development of the aquaculture sector in Egypt so as to increase productivity, profitability, and employment in the sector, and the nutritional status of poor consumers. This report represents the output of a short two-week study to better understand the market for Egyptian farmed fish. The intention of the study was to provide an output which would cut-across, and potentially benefit, all five of the project outcomes.