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  • 1
    Electronic Resource
    Electronic Resource
    Tests to confirm quantitative sampling of young fish by the Bagenal buoyant net (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 9 (1979), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. Buoyant nets had been developed and used for several years to sample young fish quantitatively. Tests were carried out to verify the quantitative aspect of sampling. Using nets of 1-m and 0.5-m mouth diameter, over several months, the catches of the two net sizes were compared. There was no significant difference in the lengths of the fish caught in the two sizes of net nor in the population estimates derived from their catches. These results indicate that there is no avoidance of the nets and that they can be considered to sample quantitatively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1979.tb01518.x
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  • 2
    Electronic Resource
    Electronic Resource
    The relative effects of enrichment and climate change on the long-term dynamics of Daphnia in Esthwaite Water, Cumbria (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 23 (1990), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. The factors influencing the seasonal and inter-annual variations in the numbers of Daphnia hyalina in Esthwaite Water between 1956 and 1972 are analysed. Esthwaite Water has always been eutrophic. but the phosphorus and nitrogen loadings to the lake increased significantly in the mid 1960s.2. Qualitatively, the phytoplankton and zooplankton populations in the lake changed relatively little during the period of study. Quantitatively, however, eutrophic species of algae became more abundant and the numbers of Eudiaptomus declined as the numbers of Daphnia increased.3. The seasonal dynamics of the Daphnia was governed partly by the seasonal temperature cycle, and partly by the periodicity of edible algae. The birth rate of the Daphnia was constrained by temperature from January to April and from October to December. At other times their rate of increase was governed by the relative abundance of edible and inedible algae.4. Edible and inedible species of algae tended 10 appear in a recurring annual sequence. Diatoms such as Asterionella were abundant in the spring, the early summer phytoplankton was dominated by edible flagellates, but inedible algae such as Aphanizomenon and Microcystis become dominant later in the year.5. Daphnia could only reproduce in late summer when there were periodic regrowths of edible algae. Such regrowths were most likely to occur when there had been some entrainment of deep nutrients by episodic wind mixing. Calm weather encouraged the growth of blue-green algae that effectively‘blocked’the development of the Daphnia for the remainder of the summer.6. The factors that controlled the seasonal dynamics of the Daphnia also influenced the average number recorded in a particular year. The average number of Daphnia increased in the early sixties when Cryptomonas was abundant and decreased in the late sixties when blooms of Aphanizomenon appeared in mid summer. Detailed analyses showed that a similar increase in the numbers of Aphanizometion had occurred in the late fifties. The critical factor throughout was the prolonged period of calm resulting in stable stratification.7. This ‘weather’ effect was highlighted by comparing de-trended timeseries of Daphnia and Aphanizometion numbers with a simple measure of thermocline stability. De-trending removed the superimposed effects of progressive enrichment and revealed a 10-year cycle of thermocline stability that matched the temperature cycle recently reported in Windermere, These cycles are related to the movement of weather systems in the Atlantic so could change if the pattern of atmospheric circulation is altered by global warming.8. The possible effects of climate change on Daphnia dynamics are discussed in relation to the findings in Esthwaite Water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1990.tb00253.x
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  • 3
    Electronic Resource
    Electronic Resource
    The influence of the North Atlantic Oscillation on the physical, chemical and biological characteristics of four lakes in the English Lake District (2004)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 49 (2004), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Thirty-six years of winter meteorological and limnological measurements from four lakes in the English Lake District are analysed and related to variations in the North Atlantic Oscillation (NAO). Winter weather conditions were strongly influenced by the NAO with mild, wet winters being associated with strongly positive values of the NAO index (NAOI).2. Lake surface and bottom temperatures were strongly positively correlated with the NAOI, with the highest correlations being recorded in the shallower lakes.3. Variations in the NAOI also had a significant effect on the winter concentration of nitrate. In all the lakes, there was a significant negative correlation between the NAOI and the detrended winter concentration of nitrate. The key driving variable was the local air temperature, which appeared to limit the quantity of nitrate reaching the lake by increasing the amount assimilated in the surrounding catchment in mild winters.4. Dissolved reactive phosphorus (DRP) concentrations were not significantly correlated with the NAOI in the two larger basins but significant positive correlations were recorded in the two smaller lakes. The key driving variable was the local rainfall with higher DRP concentrations being recorded after heavy rain in the lakes with a short retention time.5. The NAOI-related changes in rainfall also influenced the phytoplankton. In wet winters the concentration of chlorophyll in the two smaller lakes with the shortest retention time was lower and the spring growth of Asterionella formosa was delayed in the smallest lake.6. These differential responses demonstrate how the large-scale effects associated with the NAO can be ‘filtered’ by the physical characteristics of a particular site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.2004.01223.x
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  • 4
    Electronic Resource
    Electronic Resource
    Sex ratio changes in the long-term Windermere pike and perch sampling program (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Ecology of freshwater fish 8 (1999), S. 0 
    Details
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract– Analysis of the Windermere (England), Perca fluviatilis (1965–1997) and Esox lucius (1943-1997) fishery data indicates there have been substantial changes in sex ratios through time. In the case of perch, a 1976 perch disease outbreak substantially skewed the sex ratio in favor of females. It took over a decade for the fishery to recover to its pre-1976 state. In the case of pike, both catch and year-class data are female biased, but this bias has significantly weakened through time. This trend towards proportionately more males through time may reflect an effect of increasing spring temperatures or an evolutionary or phenotypic response to female-biased fishing pressure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0633.1999.tb00057.x
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  • 5
    Electronic Resource
    Electronic Resource
    Biotic and abiotic influences on the recruitment of male perch in Windermere, U.K. (2004)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 65 (2004), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Perch Perca fluviatilis recruitment (based on the catch per unit effort, CPUE, of 2 or 3 year male perch) varied greatly from 1941 to 1995 in Windermere, U.K., with year class strengths strongly synchronous between the two basins of this temperate, mesotrophic lake. Statistically significant modified Ricker (Saila-Lorda) stock-recruitment curves could be fitted to data from three of four sampling sites, while the presence of widespread disease and late summer water temperature were also important explanatory variables. Multiple-regression analyses revealed no influences of pike Esox lucius recruitment, zooplankton abundance, or the climatic influences (i.e. North Atlantic Oscillation and displacement of the summer position of the Gulf Stream) on perch recruitment over and above associated influences from temperature. Fitted models realistically explained up to c. 60% of the observed variation in perch recruitment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0022-1112.2004.00573.x
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  • 6
    Electronic Resource
    Electronic Resource
    Responses of the phytoplankton to a deliberate attempt to raise the trophic status of an acidic, oligotrophic mountain lake (1998)
    Springer
    Hydrobiologia 369-370 (1998), S. 127-131 
    Details
    ISSN: 1573-5117
    Keywords: phytoplankton ; trophic status ; phosphorus ; eutrophication ; species composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The paper reports the impact of a sharp artificial enrichment of the available phosphorus in a small, acidic and oligotrophic corrie lake and its effects upon the phytoplankton supported. Annual average chlorophyll increased tenfold within two years, from ∼ 1.2 to 12.6 µg chl a l-1, but the species represented by large populations are the same as previously. Chrysophyte species, however, make up a smaller fraction of the total crop.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017022631862
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  • 7
    Electronic Resource
    Electronic Resource
    The population dynamics of Keratella cochlearis in a hypereutrophic tarn and the possible impact of predation by young roach (1987)
    Springer
    Hydrobiologia 147 (1987), S. 221-227 
    Details
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Priest Pot is a shallow hypereutrophic tarn that supports large numbers of rotifers and young roach (Rutilus rutilus (L).). In this paper we describe the planktonic rotifer community of the tarn and show that the young roach feed extensively on Keratella cochlearis. A two year study of the population dynamics of K. cochlearis, nevertheless, failed to detect any obvious demographic effects of roach predation. Some general comparisons of fish biomass and rotifer production suggest that the fish are unlikely to influence the development of their rotifer prey in such a productive system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025746
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