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  • 1
    Electronic Resource
    Electronic Resource
    Oceanography Fish do not avoid survey vessels (2000)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 404 (2000), S. 35-36 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The precarious condition of the world's fisheries is making ever-greater demands of the scientific assessment of fish stocks. Traditional assessments that rely on commercial catch statistics can have major shortcomings (as shown, for example, by the collapse of Canada's northern cod ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35003648
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    Paper (German National Licenses)
    Fulltext
  • 2
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    Effect of mobile ions on ultrathin silicon-on-insulator-based sensors (2010)
    American Institute of Physics
    Details
    Publication Date: 2010-07-19
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics
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  • 3
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    Using fishery-dependent data to inform the development and operation of a co-management initiative to reduce cod mortality and cut discards (2011)
    Oxford University Press
    Details
    Publication Date: 2011-11-24
    Description: Holmes, S. J., Bailey, N., Campbell, N., Catarino, R., Barratt, K., and Gibb, A., and Fernandes, P. G. 2011. Using fishery-dependent data to inform the development and operation of a co-management initiative to reduce cod mortality and cut discards. – ICES Journal of Marine Science, 68: 1679–1688. The Scottish conservation credits scheme is a voluntary programme introduced in 2008, designed to reduce mortality and discarding of cod in line with EU Common Fisheries Policy management objectives. The scheme was expanded in 2009, building on the initial elements of real-time closures (RTCs) and gear requirements. Various measures were agreed in a co-management framework involving fishers, non-governmental organizations, government officials, and scientists. The main objective was to encourage cod avoidance and the reduction of cod discards using spatial tools such as RTCs and seasonal closures, along with gear options that reduce cod capture. The scheme was incentivized by rewarding participation with additional days at sea. Real-time monitoring was carried out with extensive use of fishery-dependent information, allowing management to be adapted as required and to address emerging problems. The use of vessel monitoring system data, logbook records, fishers’ knowledge, and observer data is described in terms of implementing and assessing the scheme. Compliance with the closure elements of the scheme was judged to have been good, and estimated catch rates by the Scottish fleet met target criteria, but the assessed catch savings of cod from RTCs were less than predicted. Modifications to the scheme were introduced for 2010, reflecting improved knowledge and experience.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 4
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    Observations of discards in the Scottish mixed demersal trawl fishery (2011)
    Oxford University Press
    Details
    Publication Date: 2011-11-24
    Description: Fernandes, P. G., Coull, K., Davis, C., Clark, P., Catarino, R., Bailey, N., Fryer, R., and Pout, A. 2011. Observations of discards in the Scottish mixed demersal trawl fishery. – ICES Journal of Marine Science, 68: 1734–1742. The Marine Laboratory in Aberdeen (now part of Marine Scotland Science) has operated a scientific observer programme in the Scottish mixed demersal trawl fishery for more than 20 years. Discards of the main demersal species (cod, haddock, whiting, and saithe) have been sampled according to a stratified design based on gear, area, and month, with quota sampling used to select vessels. The aim of the programme is to estimate the quantity (at age) of the discarded component of the catch, to contribute to estimates of total catch for these species so that assessments of each stock can be made. Trends of discards from this observer programme from 1987 to 2009 are reported. Notable features include the sudden practice of discarding marketable cod in 2007. This was due to a number of factors including, paradoxically, improvements in compliance measures which meant that fish could no longer be landed illegally. Methods for raising the sampled discards to the level of the fleet are also explored and discussed in relation to changes in discarding patterns. These are particularly relevant at a time when, in northern Europe at least, there is a move towards standardizing methods for estimating total quantities of discards.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 5
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    Possible unconventional superconductivity in substituted BaFe2As2 revealed by magnetic pair-breaking studies (2014)
    Springer Nature
    Details
    Publication Date: 2014-09-02
    Description: The possible existence of a sign-changing gap symmetry in BaFe2As2-derived superconductors (SC) has been an exciting topic of research in the last few years. To further investigate this subject we combine Electron Spin Resonance (ESR) and pressure-dependent transport measurements to investigate magnetic pair-breaking effects on BaFe1.9M0.1As2 (M = Mn, Co, Cu, and Ni) single crystals. An ESR signal, indicative of the presence of localized magnetic moments, is observed only for M = Cu and Mn compounds, which display very low SC transition temperature (Tc) and no SC, respectively. From the ESR analysis assuming the absence of bottleneck effects, the microscopic parameters are extracted to show that this reduction of Tc cannot be accounted by the Abrikosov-Gorkov pair-breaking expression for a sign-preserving gap function. Our results reveal an unconventional spin- and pressure-dependent pair-breaking effect and impose strong constraints on the pairing symmetry of these materials. Scientific Reports 4 doi: 10.1038/srep06252
    Electronic ISSN: 2045-2322
    Topics: Natural Sciences in General
    Published by Springer Nature
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  • 6
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    Jupiter's North Equatorial Belt expansion and thermal wave activity ahead of Juno's arrival (2017)
    Wiley
    Details
    Publication Date: 2017-05-26
    Description: The dark colors of Jupiter's North Equatorial Belt (NEB, 7 − 17 ∘ N) appeared to expand northward into the neighboring zone in 2015, consistent with a 3-5 year cycle. Inversions of thermal-IR imaging from the Very Large Telescope revealed a moderate warming and reduction of aerosol opacity at the cloud tops at 17 − 20 ∘ N, suggesting subsidence and drying in the expanded sector. Two new thermal waves were identified during this period: (i) an upper tropospheric thermal wave (wavenumber 16-17, amplitude 2.5 K at 170 mbar) in the mid-NEB that was anti-correlated with haze reflectivity; and (ii) a stratospheric wave (wavenumber 13-14, amplitude 7.3 K at 5 mbar) at 20 − 30 ∘ N. Both were quasi-stationary, confined to regions of eastward zonal flow, and are morphologically similar to waves observed during previous expansion events.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Classification of Southern Ocean krill and icefish echoes using random forests (2016)
    Oxford University Press
    Details
    Publication Date: 2016-09-24
    Description: Target identification remains a challenge for acoustic surveys of marine fauna. Antarctic krill, Euphausia superba , are typically identified through a combination of expert scrutiny of echograms and analysis of differences in mean volume backscattering strengths (S V ; dB re 1 m –1 ) measured at two or more echosounder frequencies. For commonly used frequencies, however, the differences for krill are similar to those for many co-occurring fish species that do not possess swimbladders. At South Georgia, South Atlantic, one species in particular, mackerel icefish, Champsocephalus gunnari , forms pelagic aggregations, which can be difficult to distinguish acoustically from large krill layers. Mackerel icefish are currently surveyed using bottom-trawls, but the resultant estimates of abundance may be biased because of the species' semi-pelagic distribution. An acoustic estimate of the pelagic component of the population could indicate the magnitude of this bias, but first a reliable target identification method is required. To address this, random forests (RFs) were generated using acoustic and net sample data collected during surveys. The final RF classified as krill, icefish, and mixed aggregations of weak scattering fish species with an overall estimated accuracy of 95%. Minimum S V , mean aggregation depth (m), mean distance from the seabed (m), and geographic positional data were most important to the accuracy of the RF. Time-of-day and the difference between S V at 120 kHz (S V 120 ) and that at 38 kHz (S V 38 ) were also important. The RF classification resulted in significantly higher estimates of backscatter apportioned to krill when compared with widely applied identification methods based on fixed and variable ranges of S V 120 –S V 38 . These results suggest that krill density is underestimated when those S V -differencing methods are used for target identification. RFs are an objective means for target identification and could enhance the utility of incidentally collected acoustic data.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 8
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    Additional evidence for fisheries acoustics: small cameras and angling gear provide tilt angle distributions and other relevant data for mackerel surveys (2016)
    Oxford University Press
    Details
    Publication Date: 2016-09-24
    Description: Fisheries acoustics surveys are effective tools in marine resource assessment and marine ecology. Significant advances have occurred in recent years with the application of multiple and broadband frequencies to enable remote species identification. There is, however, still the need to obtain additional evidence for identification, and the estimation of the size and tilt angle distribution of fish, which influences their acoustic target strength. The former two requirements are usually met by obtaining simultaneous net samples: there are limited, if any, recognized successful techniques for the latter. Here, two alternative tools for obtaining evidence for all three requirements are examined: angling gear and small video cameras. These tools were deployed during surveys of Atlantic mackerel ( Scomber scombrus ). In 2014, angling was actually more efficient than pelagic trawling (the standard technique) and over two survey periods (2012 and 2014) provided length frequency distributions that were not significantly different. A small video camera was deployed into mackerel schools, providing species identification and fish orientation. Image analysis was then applied, producing tilt-angle distributions of free swimming wild mackerel for the first time. Mean tilt angles from three deployments were very variable with 95% of observations falling between –70° and 39° with evidence of a multinomial frequency distribution. A video equipped lander was also deployed onto the type of rocky seabed where deployment of a trawl would be impossible: this confirmed the presence of Norway pout and suggested it was the dominant scatterer on this type of seabed. These techniques are complementary to traditional trawling methods, but provide additional insights into fish behaviour whilst satisfying standard requirements of identification and supplying biological samples. Crucially, the small cameras deployed approximate the size of the animals under observation and allow for measurement of behaviour (specifically tilt) that are more likely to represent those conditions encountered during surveying.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 9
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    Passive and active, predator and prey: using acoustics to study interactions between cetaceans and forage fish (2016)
    Oxford University Press
    Details
    Publication Date: 2016-09-24
    Description: Fisheries acoustics surveys provide platforms for deploying passive acoustic equipment to detect cetacean vocalizations. Passive acoustic methods are developing as viable alternatives to visual surveys, particularly for small, inconspicuous species such as the harbour porpoise ( Phocoena phocoena ). Passive acoustic monitoring using a towed hydrophone array was carried out during an acoustic survey of clupeids in the Clyde Sea and surrounding sea lochs to identify spatial relationships between porpoises and their prey. Methods were developed to process passive acoustic data, successfully identifying porpoise echolocation clicks while discriminating them from the transmitted 120-kHz echosounder pulse and its reflections. To date, this has been a confounding factor which has made these survey techniques potentially incompatible. The highest biomass of pelagic fish was detected in the northernmost parts of the survey region, as were the largest number of porpoises. A moving average was used to examine the scale of the relationships identified, and it was found that while porpoises show no significant preferences for pelagic prey numbers at the smallest scales, they do show significant avoidance of larger areas (5+ km) with very low pelagic fish biomass. This study demonstrates that high-frequency passive acoustic monitoring can be used effectively alongside multifrequency fisheries echosounder surveys to provide novel insights into the trophic interactions between these species, and that further work will hopefully prove useful in improving the efficacy of management strategies for harbour porpoises.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 10
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    Environmental isotopes (15N and 18O) in the assessment of groundwater degradation: Aveiro Quaternary aquifer (NW Portugal) (2009)
    Springer
    Details
    Publication Date: 2009-06-27
    Print ISSN: 0236-5731
    Electronic ISSN: 1588-2780
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Published by Springer
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