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  1. Article: Survival and growth compared between wild and farmed eel stocked in freshwater ponds

    Pedersen, M.I / G. Rasmussen / N. Jepsen

    Fisheries research. 2017 Oct., v. 194

    2017  

    Abstract: To evaluate the efficiency of eel stocking, we compared the survival and growth of wild eels (2–5g) with that of “farmed” eels (3–6g). Wild eels were caught in a river and farmed eels came from a farm, where wild imported glass eels are cultured. Two ... ...

    Abstract To evaluate the efficiency of eel stocking, we compared the survival and growth of wild eels (2–5g) with that of “farmed” eels (3–6g). Wild eels were caught in a river and farmed eels came from a farm, where wild imported glass eels are cultured. Two experiments of 5–12 month duration were conducted in a series of shallow, open ponds of approximately 200m2. Wild and farmed eels were batch tagged, mixed and released in the ponds at an initial density of 0.5 individual/m2. Survival was rather high (34–88%) with variations between ponds. No significant difference in survival was found between wild and farmed during the first 5 month in both experiments. Growth rates were significantly higher for farmed eels compared to wild eels in both experiments. The results show that farmed eels performed better than wild eels. In regions with low recruitment the eel population may be increased by importing glass eels, stocked directly or stocked as on-grown farmed eel. The optimal size for stocking (between glass- and 3g eels) may be determined through future studies.
    Keywords eel ; farmed fish ; farms ; freshwater ; ponds ; rivers
    Language English
    Dates of publication 2017-10
    Size p. 112-116.
    Publishing place Elsevier B.V.
    Document type Article
    ZDB-ID 406532-3
    ISSN 0165-7836
    ISSN 0165-7836
    DOI 10.1016/j.fishres.2017.05.013
    Database NAL-Catalogue (AGRICOLA)

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    In stock of ZB MED Bonn / Germany

    Z 3666: Show issues

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  2. Article ; Online: Trends in polar ozone loss since 1989

    A. Pazmiño / F. Goutail / S. Godin-Beekmann / A. Hauchecorne / J.-P. Pommereau / M. P. Chipperfield / W. Feng / F. Lefèvre / A. Lecouffe / M. Van Roozendael / N. Jepsen / G. Hansen / R. Kivi / K. Strong / K. A. Walker

    Atmospheric Chemistry and Physics, Vol 23, Pp 15655-

    potential sign of recovery in the Arctic ozone column

    2023  Volume 15670

    Abstract: Ozone depletion over the polar regions is monitored each year by satellite- and ground-based instruments. In this study, the vortex-averaged ozone loss over the last 3 decades is evaluated for both polar regions using the passive ozone tracer of the ... ...

    Abstract Ozone depletion over the polar regions is monitored each year by satellite- and ground-based instruments. In this study, the vortex-averaged ozone loss over the last 3 decades is evaluated for both polar regions using the passive ozone tracer of the chemical transport model TOMCAT/SLIMCAT and total ozone observations from Système d'Analyse par Observation Zénithale (SAOZ) ground-based instruments and Multi-Sensor Reanalysis (MSR2). The passive-tracer method allows us to determine the evolution of the daily rate of column ozone destruction and the magnitude of the cumulative column loss at the end of the winter. Three metrics are used in trend analyses that aim to assess the ozone recovery rate over both polar regions: (1) the maximum ozone loss at the end of the winter, (2) the onset day of ozone loss at a specific threshold, and (3) the ozone loss residuals computed from the differences between annual ozone loss and ozone loss values regressed with respect to sunlit volume of polar stratospheric clouds (VPSCs). This latter metric is based on linear and parabolic regressions for ozone loss in the Northern Hemisphere and Southern Hemisphere, respectively. In the Antarctic, metrics 1 and 3 yield trends of − 2.3 % and − 2.2 % per decade for the 2000–2021 period, significant at 1 and 2 standard deviations ( σ ), respectively. For metric 2, various thresholds were considered at the total ozone loss values of 20 %, 25 %, 30 %, 35 %, and 40 %, all of them showing a time delay as a function of year in terms of when the threshold is reached. The trends are significant at the 2 σ level and vary from 3.5 to 4.2 d per decade between the various thresholds. In the Arctic, metric 1 exhibits large interannual variability, and no significant trend is detected; this result is highly influenced by the record ozone losses in 2011 and 2020. Metric 2 is not applied in the Northern Hemisphere due to the difficulty in finding a threshold value in enough of the winters. Metric 3 provides a negative trend in Arctic ozone loss residuals ...
    Keywords Physics ; QC1-999 ; Chemistry ; QD1-999
    Subject code 290
    Language English
    Publishing date 2023-12-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: Trends and annual cycles in soundings of Arctic tropospheric ozone

    B. Christiansen / N. Jepsen / R. Kivi / G. Hansen / N. Larsen / U. S. Korsholm

    Atmospheric Chemistry and Physics, Vol 17, Pp 9347-

    2017  Volume 9364

    Abstract: Ozone soundings from nine Nordic stations have been homogenized and interpolated to standard pressure levels. The different stations have very different data coverage; the longest period with data is from the end of the 1980s to 2014. At each pressure ... ...

    Abstract Ozone soundings from nine Nordic stations have been homogenized and interpolated to standard pressure levels. The different stations have very different data coverage; the longest period with data is from the end of the 1980s to 2014. At each pressure level the homogenized ozone time series have been analysed with a model that includes both low-frequency variability in the form of a polynomial, an annual cycle with harmonics, the possibility for low-frequency variability in the annual amplitude and phasing, and either white noise or noise given by a first-order autoregressive process. The fitting of the parameters is performed with a Bayesian approach not only giving the mean values but also confidence intervals. The results show that all stations agree on a well-defined annual cycle in the free troposphere with a relatively confined maximum in the early summer. Regarding the low-frequency variability, it is found that Scoresbysund, Ny Ålesund, Sodankylä, Eureka, and Ørland show similar, significant signals with a maximum near 2005 followed by a decrease. This change is characteristic for all pressure levels in the free troposphere. A significant change in the annual cycle was found for Ny Ålesund, Scoresbysund, and Sodankylä. The changes at these stations are in agreement with the interpretation that the early summer maximum is appearing earlier in the year. The results are shown to be robust to the different settings of the model parameters such as the order of the polynomial, number of harmonics in the annual cycle, and the type of noise.
    Keywords Physics ; QC1-999 ; Chemistry ; QD1-999
    Subject code 551
    Language English
    Publishing date 2017-08-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article: Cormorant predation overlaps with fish communities and commercial-fishery interest in a Swedish lake

    Ovegård, M. K / K. Öhman / J. S. Mikkelsen / N. Jepsen

    Marine & freshwater research. 2017, v. 68, no. 9

    2017  

    Abstract: The increase of the fish-eating cormorant (Phalacrocorax carbo sinensis) in Europe has resulted in conflicts with fisheries. In Lake Roxen, Sweden, cormorants are blamed for causing a decrease in fishery catches. To study and describe the potential ... ...

    Abstract The increase of the fish-eating cormorant (Phalacrocorax carbo sinensis) in Europe has resulted in conflicts with fisheries. In Lake Roxen, Sweden, cormorants are blamed for causing a decrease in fishery catches. To study and describe the potential effects that cormorants may have had on fish in the lake, their diet was analysed in relation to fish catches in gill-net surveys and fishery catches. Estimates of predation were achieved by ‘tag and recovery’ on eel, pike-perch and perch. Cormorants predated on the most common species and sizes, which were mainly smaller perch, ruffe and roach (mean sizes of 9, 8 and 13cm respectively). Tag recoveries from perch, eel and pike-perch detected predation estimates of 14, 7 and 15% respectively. From a highly eutrophic state, the lake has shown improvements in water quality and a development towards larger predatory fish was expected, but the results from gill-net surveys did not show this. Results indicated that cormorants and fisheries may both be responsible, but because cormorants remove more fish, they may be the main factor for the lack of recovery of large predatory fish. Their predation keeps recruitment high, but the number of fish that reach large sizes remains low.
    Keywords Gymnocephalus cernua ; Phalacrocorax carbo sinensis ; Sander lucioperca ; diet ; eel ; eutrophication ; fish communities ; fisheries ; gillnets ; lakes ; perch ; predation ; predatory fish ; surveys ; water quality ; Sweden
    Language English
    Size p. 1677-1685.
    Publishing place CSIRO Publishing
    Document type Article
    ZDB-ID 1283028-8
    ISSN 1323-1650
    ISSN 1323-1650
    DOI 10.1071/MF16227
    Database NAL-Catalogue (AGRICOLA)

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    In stock of ZB MED Bonn / Germany

    Z 4948: Show issues

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  5. Article ; Online: EUBREWNET RBCC-E Huelva 2015 Ozone Brewer Intercomparison

    A. Redondas / V. Carreño / S. F. León-Luis / B. Hernández-Cruz / J. López-Solano / J. J. Rodriguez-Franco / J. M. Vilaplana / J. Gröbner / J. Rimmer / A. F. Bais / V. Savastiouk / J. R. Moreta / L. Boulkelia / N. Jepsen / K. M. Wilson / V. Shirotov / T. Karppinen

    Atmospheric Chemistry and Physics, Vol 18, Pp 9441-

    2018  Volume 9455

    Abstract: From 25 May to 5 June 2015, the 10th regional intercomparison campaign of the Regional Brewer Calibration Center – Europe (RBCC-E) was held at El Arenosillo atmospheric sounding station of the Instituto Nacional de Técnica Aeroespacial (INTA). This ... ...

    Abstract From 25 May to 5 June 2015, the 10th regional intercomparison campaign of the Regional Brewer Calibration Center – Europe (RBCC-E) was held at El Arenosillo atmospheric sounding station of the Instituto Nacional de Técnica Aeroespacial (INTA). This campaign was jointly conducted by COST Action ES1207 EUBREWNET and the Area of Instrumentation and Atmospheric Research of INTA. A total of 21 Brewers, 11 single- and 10 double-monochromator instruments from 11 countries participated and were calibrated for total column ozone (TOC) and solar UV irradiance. In this 2015 campaign we have introduced a formal approach to the characterisation of the internal instrumental stray light, the filter non-linearity and the algorithm for correcting for its effects on the TOC calculations. This work shows a general overview of the ozone comparison and the evaluation of the correction of the spectral stray light effect for the single-monochromator Brewer spectrophotometer, derived from the comparison with a reference double-monochromator Brewer instrument. At the beginning of the campaign, 16 out of the 21 participating Brewer instruments agreed within better than ±1 %, and 10 instruments agreed within better than ±0.5 % considering data with ozone slant column between 100 and 900 DU, which does not require instrumental stray light correction.
    Keywords Physics ; QC1-999 ; Chemistry ; QD1-999
    Language English
    Publishing date 2018-07-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Article ; Online: Aerosol optical depth in the European Brewer Network

    J. López-Solano / A. Redondas / T. Carlund / J. J. Rodriguez-Franco / H. Diémoz / S. F. León-Luis / B. Hernández-Cruz / C. Guirado-Fuentes / N. Kouremeti / J. Gröbner / S. Kazadzis / V. Carreño / A. Berjón / D. Santana-Díaz / M. Rodríguez-Valido / V. De Bock / J. R. Moreta / J. Rimmer / A. R. D. Smedley /
    L. Boulkelia / N. Jepsen / P. Eriksen / A. F. Bais / V. Shirotov / J. M. Vilaplana / K. M. Wilson / T. Karppinen

    Atmospheric Chemistry and Physics, Vol 18, Pp 3885-

    2018  Volume 3902

    Abstract: Aerosols play an important role in key atmospheric processes and feature high spatial and temporal variabilities. This has motivated scientific interest in the development of networks capable of measuring aerosol properties over large geographical areas ... ...

    Abstract Aerosols play an important role in key atmospheric processes and feature high spatial and temporal variabilities. This has motivated scientific interest in the development of networks capable of measuring aerosol properties over large geographical areas in near-real time. In this work we present and discuss results of an aerosol optical depth (AOD) algorithm applied to instruments of the European Brewer Network. This network is comprised of close to 50 Brewer spectrophotometers, mostly located in Europe and adjacent areas, although instruments operating at, for example, South America and Australia are also members. Although we only show results for instruments calibrated by the Regional Brewer Calibration Center for Europe, the implementation of the AOD algorithm described is intended to be used by the whole network in the future. Using data from the Brewer intercomparison campaigns in the years 2013 and 2015, and the period in between, plus comparisons with Cimel sun photometers and UVPFR instruments, we check the precision, stability, and uncertainty of the Brewer AOD in the ultraviolet range from 300 to 320 nm. Our results show a precision better than 0.01, an uncertainty of less than 0.05, and, for well-maintained instruments, a stability similar to that of the ozone measurements. We also discuss future improvements to our algorithm with respect to the input data, their processing, and the characterization of the Brewer instruments for the measurement of AOD.
    Keywords Physics ; QC1-999 ; Chemistry ; QD1-999
    Subject code 620
    Language English
    Publishing date 2018-03-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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