Evaluating the effects of catch-and-release angling on Cape stumpnose Rhabdosargus holubi in a South African estuary     

NK Arkert  A-R Childs  MC Parkinson  AC Winkler  E Butler  S Mannheim 《African Journal of Marine Science》2018,40(3):235-244

Fisheries managers are increasingly promoting catch-and-release (C&R) to manage recreationally angled fish stocks. Despite this, there is a scarcity of information on the effects of C&R on estuarine-dependent species. Cape stumpnose Rhabdosargus holubi dominates the recreational fisheries catch and provides an important source of food for subsistence fishers in some temperate South African estuaries. The health and survival of R. holubi exposed to a C&R event was investigated by examining their physiological stress response (blood glucose and lactate), reflex impairment (reflex action mortality predictors [RAMP]) and short-term (12-hour) survival. Fish were captured and exposed to one of three air-exposure treatments: 0 s, 30 s or 90 s. Stress and health were measured either immediately (immediate) or one hour after (delayed) the C&R event. There was no significant difference in blood glucose between air-exposure treatments, but there was a significant difference between the mean immediate and delayed glucose levels within each treatment (F_(2,143) = 81.8, p < 0.01). In contrast, blood lactate level was significantly higher in the 90-s treatment (p < 0.05). Immediate blood lactate levels were significantly lower than the delayed samples for each treatment (F = 4.29, p = 0.02; n = 169). Although all fish exhibited at least one reflex impairment, the RAMP score was significantly higher in the 90-s air-exposure treatment (H_(2,86) = 9.73, p = 0.007). Also, RAMP scores were significantly lower in the delayed samples (p < 0.01). Although short-term mortality was relatively low (2.3%) for this species, it was highest in the 90-s treatment (7%). These results suggest that physiological stress is higher when R. holubi are exposed to longer periods of air exposure and that the physiological stress of fish subject to a C&R event is best measured after a delay.  相似文献   

TRIFFID observations of the cores of the three globular clusters M15, M92 and NGC 6712     

S. Ó Tuairisg  R. F. Butler  A. Shearer  R. M. Redfern  D. Butler  A. Penny 《Monthly notices of the Royal Astronomical Society》2003,345(3):960-980

We present the results of TRIFFID simultaneous V - and B -band observations of the cores of the globular clusters M15, M92 and NGC 6712. A variability search of their dense centres was made feasible through performing post-exposure image sharpening on the images, increasing the image resolution by a factor of ∼2. The isis implementation of the image subtraction technique developed by Alard & Lupton was then used to detect flux variations in our image sets. We have obtained periods for all observable variables (in our field of view) in NGC 6712 and we have found two new RR Lyrae variables (an RRab and an RRc). We have confirmed three variables in our field of view of the M92. For M15, we detect 48 variables in our field of view, 23 of which are new discoveries. We obtain periods and amplitudes for all variables and classify new ones based on the light-curve shape, the most significant period and the mean magnitude in the V band. Among the detected RR Lyrae we find 19 RRc, 12 RRab and two RRd types. In the subsequent analysis we find a marked increase in RRc over RRab variables in the core. In a refined procedure to search for fainter objects we find no dwarf novae in our field of view of M15. Simulations performed on the data set to quantify our sensitivity to such objects indicate that an upper limit of 10 dwarf novae (at 92 per cent probability) exist in our field of view. The implications this result has on globular clusters are discussed.  相似文献   

The significance of Messinian occurrences of Globorotalia margaritae and Globorotalia puncticulata in Sicily     

R.W.H. Butler  H.M. Pedle  R. Maniscalco  M. Grasso  E. McClelland  B. Finegan 《地学学报》1996,8(1):59-64

Globorotalia puncticulata and Globorotalia margaritae are critical species that define internationally recognized planktonic foraminiferal biozones in the Pliocene. These biozones are defined from stratotype sections on Sicily and their fauna are commonly considered to have been introduced to the Mediterranean after an influx of Atlantic water that terminated the late Miocene desiccation of the basin. Herein new discoveries of these species in rocks that predate the late Miocene desiccation are described. These data are supported by magneto- and lithostratigraphy that have been integrated at a single continuous section. Not only do these discoveries question the existing foraminiferal biozone stratigraphy, they also suggest new models for the dispersal of planktonic species. It is proposed that Globorotalia puncticulata and perhaps even Globorotalia margaritae evolved in the Mediterranean during earliest Messinian times (during or before chron C3Bn1n) and dispersed into the Atlantic. This suggests that a marine connection remained between the two sea areas until at least chron C3An.1n. Using the existing geomagnetic polarity time scale, these occurrences are some 2 Myr earlier than previously recorded in the Mediterranean. The distribution of G. margaritae and G. puncticulata in Mediterranean sections is likely to reflect palaeoenvironment or the preservation of deposits rather than the absolute age of the sediments.  相似文献   

Observation of MKN 501 at gamma-ray energies     

L. Bassani  R. C. Butler  A. J. Dean  G. Di Cocco  A. Della Ventura  F. Perotti  G. Villa 《Astrophysics and Space Science》1982,82(2):311-316

During a balloon flight in September 1979 of the MISO low-energy -ray telescope, the BL Lac-object MkN 501 was studied in the hard X-ray range above 30 keV and in the low energy -ray range up to 19 MeV. No statistically significant X- and -ray fluxes were detected. The implications of the upper limits obtained are discussed in the light of the relativistic jet theories recently proposed.  相似文献   

UV Laser Ablation ICP-MS: Some Applications in the Earth Sciences   总被引：4，自引：0，他引：4  

Robert W. Nesbitt  Takafumi Hirata  Ian B. Butler  James A. Milton 《Geostandards and Geoanalytical Research》1997,21(2):231-243

This study reports a series of applications of UV laser ablation ICP-MS in the geological sciences. The advantages and disadvantages of the PQ "S" option and the use of nitrogen in the carrier gas are discussed. A general problem common to all ablation techniques is the calibration technique and experiments involving synthetic calibration samples are covered. Zircon geochemistry and geochronology by LA-ICP-MS are discussed and data are presented for REE, Hf and U for a standard zircon (91500) as well as a series of zircons from Zimbabwe. The potential of using Ce and Eu anomalies in petrologic studies is illustrated by zircons from a fractionated gabbroic-granite in the Urals. The potential of the LA-ICP-MS method to utilise standard X-ray fluorescence glass discs is demonstrated as a useful semi-quantitative tool in determining REE patterns. LA-ICP-MS is a powerful tool in the analysis of the platinum group elements (and Re) and some examples are given in the successful application of the technique to partitioning in iron meteorites.  相似文献   

The possible connection between ionization in the atmosphere by cosmic rays and low level clouds     

E. Pall  C.J. Butler  K. O&#x;Brien 《Journal of Atmospheric and Solar》2004,66(18):14003

Recent analysis of monthly mean cloud data from the International Satellite Cloud Climatology Project uncovered a strong correlation between low cloud and the cosmic ray flux for extensive regions of the Earth. Additional data have been recently released covering the period up to September 2001 with which we have made a new study of the geographical variation of the correlation between low cloud and predicted ionization level from cosmic rays at an altitude of 2 km. When analysed globally, we find that the correlations do not correspond to the latitude variation of cosmic ray flux and they are not field significant. Nonetheless they appear to be marginally field significant over broad latitude and longitude bands with a peak positive correlation at 50 degrees North and South and a tendency to negative correlation at lower latitudes. The correlation is strongest over the North and South Atlantic. Several of these features are consistent with the predictions of the electroscavenging process.We use a simple model to calculate the climatic impact should the correlation be confirmed. We show that, under the most favorable conditions, a reduction in low cloud cover since the late 19th century, combined with the direct forcing by solar irradiance can explain a significant part of the global warming over the past century, but not all. However, this computation assumes that there is no feedback or changes in cloud at other levels.  相似文献   

Anatomy of a continental subduction zone: The main mantle thrust in Northern Pakistan     

Robert W. H. Butler  David J. Prior 《International Journal of Earth Sciences》1988,77(1):239-255

The Himalayas form an ideal natural laboratory to study the deformation processes of continental crust during collision orogeny. New information is presented concerning the structural evolution of the Main Mantle thrust zone in the Himalayas of N Pakistan, in the region around Nanga Parbat. The hanging-wall lies at relatively high levels within the Kohistan arc terrane which has been emplaced onto Indian continental rocks. This thrust probably originated as a breakback structure in the hanging-wall to the pre-collisional (oceanic) subduction zone. The present hanging-wall contains a shear zone of about 1 km width developed under amphibolite facies conditions. Simple shear dominant strains have developed new fabrics parallel to the main thrust zone. However, these structures are redeformed by discrete extensional and compressional shears within about 100 m of the thrust contact, again developed under amphibolite facies conditions. The footwall consists of an old basement complex (the Nanga Parbat gneisses) overlain by a distinct suite of metasediments now at amphibolite facies. This cover assemblage of psammites, pelites and marbles with local metabasites consistently lies directly against rocks derived from the Kohistan arc along the MMT. The absence of structures suggestive of consistent rheological contrasts within the cover assemblages suggests that the vast majority of the deformation features they contain were developed only once they experienced substantial tectonic overburdens. Prior to this the Indian cover rocks will have been »passively« subducted beneath the Kohistan arc until into amphibolite facies. We discuss these inferences in terms of evolving shear zone width with time and comment on the implications for predicting the character of mid-deep crustal shear zones, particularly from seismic reflection profiles.

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Zusammenfassung Der Himalaya bildet ein ideales, natrliches Laboratorium für Untersuchungen von Deformationsprozessen in kontinentalen Krustengesteinen während der Kollision bzw. Orogenese. Hier werden neue Daten vorgelegt, die sich mit der strukturellen Entwicklung der Hauptmantelüberschiebung im Himalaya von Nordpakistan im Gebiet um den Nanga Parbat befassen. Die Hangendeinheiten oberhalb der Störung liegen in einem relativ hohen Niveau innerhalb des »Kohistan arc terrane«, das auf die indischen Kontinentalgesteine überschoben wurde. Diese Überschiebung entstand wahrscheinlich als Rücküberschiebungsstruktur im Hangenden der Subduktionszone vor der Kollision. Im Hangenden befindet sich eine ca. 1 km breite Scherzone, die sich unter amphibolitfaziellen Bedingungen gebildet hat. Die durch »simple shear« erzeugten Deformationen sind mit ihren neuen Gefügen parallel zur Hauptüberschiebungszone ausgerichtet. Die Gefüge wurden nachfolgend von Extensionsund Kompressionsbewegungen im Bereich von ca. 100 m um den Überschiebungskontakt erneut unter amphibolitfaziellen Bedingungen erfaßt und deformiert. Das Liegende der Hauptüberschiebung besteht aus einem alten Basementkomplex (den Nanga Parbat Gneisen), die von deutlich abgesetzten, amphibolitfaziellen Metasedimenten überlagert werden. Diese Sedimenthülle bestehend aus Psammiten, Peliten und Marmoren mit lokalen Metabasiten stößt entlang der MMT direkt gegen die Gesteine des Kohistanbogens. Das Fehlen von Strukturen, die auf gleichbleibende rheologische Unterschiede hinweisen würde, läßt vermuten, daß der Großteil der in ihnen enthaltenen Deformationsgefüge auf einmal während beträchtlicher tektonischer Auflast entstanden ist. Vorher wurden die indischen Hüllgesteine »passiv« unter den Kohistanbogen bis in den Bereich der Amphibolitfazies subduziert. Die Folgerungen aus der sich über die Zeit entwickelnden Breite dieser Scherzone werden diskutiert und die Bedeutung für die Vorhersage der Charakteristik von mitteltiefen krustalen Scherzonen, insbesondere in Verbindung mit seismischen Reflektionsprofilen betont.

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Résumé L'Himalaya constitue un laboratoire naturel idéal pour l'étude des processus de déformation de la croûte continentale au cours d'une orogenèse de collision. Les auteurs présentent des informations nouvelles relatives à l'évolution structurale de la zone du Main Mantle Thrust dans la région du Nanga Parbat au nord du Pakistan. Le toit de cet accident occupe un niveau assez élevé dans le «Kohistan arc Terrane» qui a été charrié sur les roches du continent indien. Le charriage doit probablement son origine à une structure en retour apparue au-dessus de la zone de subduction pré-collisionnelle (océanique). Le toit actuel de l'accident contient une zone de glissement (shear zone) épaisse d'environ 1 km et formée dans les conditions du facies des amphibolites. Les déformations engendrées par glissement simple (simple shear) ont développé de nouvelles fabriques parallèles à la surface de charriage. Cependant, dans une tranche d'une centaine de mètres à partir du contact du charriage, ces structures ont été reprises par des cisaillements extensionnels ou compressionnels, toujours dans les conditions du facies des amphibolites.Le mur de l'accident est formé d'un complexe ancien (le gneiss du Nanga Parbat) surmonté d'une série de métasédiments distincts qui présentent aujourd'hui le facies des amphibolites. Cette couverture de psammites, de pélites, de marbres et de métabasites locales est directement en contact le long du MMT avec l'arc du Kohistan. L'absence, dans cette couverture, de structures témoignant de contrastes rhéologiques marqués, suggère que la grande majorité des structures déformatives n'y ont été développées qu'après un enfouissement tectonique important. Avant cela, les roches de la couverture indienne ont dû être subductées passivement sous l'arc du Kohistan, jusqu'au facies des amphibolites. Les auteurs discutent ces conclusions en termes d'évolution temporelle d'une shear zone et en commentant les implications dans le domaine de la prédiction du caractère des shear zones de profondeur crustale moyenne, en particulier à partir des profils de sismique réflexion.

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Slug Tests in Unconfined Formations: An Assessment of the Bouwer and Rice Technique   总被引：3，自引：0，他引：3  

Z. Hyder  J. J. Butler  Jr. 《Ground water》1995,33(1):16-22

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A structural analysis of the Moine Thrust Zone between Loch Eriboll and Foinaven,NW Scotland     

Robert W.H. Butler 《Journal of Structural Geology》1982,4(1):19-29

The northern part of the Moine Thrust Zone as exposed around the valley of Srath Beag, Sutherland was developed by thrusts propagating in the tectonic transport direction. Deformation on any particular thrust surface evolved from dominantly ductile to dominantly brittle with time.The foreland has been progressively accreted onto the overriding Moine thrust sheet by duplex formation, a process which has continuously folded the roof thrust and the rocks above its hanging-wall. Fold culminations and depression can be related to lateral ramps which may give the rocks above the hanging-wall a complex history of extensional and compressional strains normal to the transport direction.Folds within the thrust zone are laterally independent because they are controlled by short lived variations in deformation style on an evolving thrust footwall topography. Therefore there may be no correlation between structures across or along the thrust zone. This variation limits the construction of balanced cross sections as structure cannot be projected onto particular section lines.  相似文献   

Characterization of the Structure of River-Bed Gravels Using Two-Dimensional Fractal Analysis   总被引：7，自引：0，他引：7  

Justin B. Butler  Stuart N. Lane  Jim H. Chandler 《Mathematical Geology》2001,33(3):301-330

This paper is concerned with the application of fractal analysis to understand the structure of water-worked gravel-bed river surfaces. High resolution digital elevation models, acquired using digital photogrammetric methods, allowed the application of two-dimensional fractal methods. Previous gravel-bed river studies have been based upon sampled profiles and hence one-dimensional fractal characterisation. After basic testing that bed elevation increments are Gaussian, the paper uses two-dimensional variogram surfaces to derive directionally dependent estimates of fractal dimension. The results identify mixed fractal behavior with two characteristic fractal bands, one associated with the subgrain scale and one associated with the grain scale. The subgrain scale characteristics were isotropic and sensitive to decisions made during the data collection process. Thus, it was difficult to differentiate whether these characteristics were real facets of the surfaces studied. The second band was anisotropic and not sensitive to data collection issues. Fractal dimensions were greater in the downstream direction than in other directions suggesting that the effects of water working are to alter the level of surface organisation, by increasing surface irregularity and hence roughness. This is an important observation as it means that water-worked surfaces may have a distinct anisotropic signal, revealed when using a fractal type analysis.  相似文献