Fisheries mismanagement     

O'Leary BC  Smart JC  Neale FC  Hawkins JP  Newman S  Milman AC  Roberts CM 《Marine pollution bulletin》2011,62(12):2642-2648

We analysed the extent to which European politicians have adhered to scientific recommendations on annual total allowable catches (TACs) from 1987 to 2011, covering most of the period of the Common Fisheries Policy (CFP). For the 11 stocks examined, TACs were set higher than scientific recommendations in 68% of decisions. Politically-adjusted TACs averaged 33% above scientifically recommended levels. There was no evidence that the 2002 reform of the CFP improved decision-making, as was claimed at the time. We modelled the effects of such politically-driven decision-making on stock sustainability. Our results suggest that political adjustment of scientific recommendations dramatically increases the probability of a stock collapsing within 40 years.In 2012 European fisheries policy will undergo a once-a-decade reform. Ten years ago radical reforms were promised but the changes failed to improve sustainability. It is likely that the 2012 reform will be similarly ineffective unless decision-making is changed so that catch allocations are based on science rather than politics.  相似文献   

The astrobiological landscape,Milan M. Ćirković. Cambridge,UK: Cambridge University Press, 2012, ISBN:9780521197755, hardback, $110, 274 p.     

SJ Guy Consolmagno 《Meteoritics & planetary science》2013,48(2):316-317

  相似文献   

    

Douglas M. Hawkins  Noel Cressie 《Mathematical Geology》1984,16(1):3-18

Geological data frequently have a heavy-tailed normal-in-the-middle distribution, which gives rise to grade distributions that appear to be normal except for the occurrence of a few outliers. This same situation also applies to log-transformed data to which lognormal kriging is to be applied. For such data, linear kriging is nonrobust in that (1)kriged estimates tend to infinity as the outliers do, and (2)it is also not minimum mean squared error. The more general nonlinear method of disjunctive kriging is even more nonrobust, computationally more laborious, and in the end need not produce better practical answers. We propose a robust kriging method for such nearly normal data based on linear kriging of an editing of the data. It is little more laborious than conventional linear kriging and, used in conjunction with a robust estimator of the variogram, provides good protection against the effects of data outliers. The method is also applicable to time series analysis.  相似文献   

U-Pb systematics of monazite and xenotime: case studies from the Paleoproterozoic of the Grand Canyon, Arizona   总被引：1，自引：0，他引：1  

D. P. Hawkins  Samuel A. Bowring 《Contributions to Mineralogy and Petrology》1997,127(1-2):87-103

Monazite is accepted widely as an important U-Pb geochronometer in metamorphic terranes because it potentially preserves prograde crystallization ages. However, recent studies have shown that the U-Pb isotopic system in monazite can be influenced by a variety of processes that partially obscure the early growth history. In this paper, we attempt to interpret complex monazite and xenotime U-Pb data from three Paleoproterozoic granite dikes exposed in the Grand Canyon. Single-crystal monazite analyses from an unfoliated granite dike spread out along concordia from the crystallization age of the dike (defined by U-Pb zircon data to be 1685 ± 1 Ma) to 1659 ± 2 Ma, a span of 26 million years. Back-scattered electron (BSE) imaging reveals that magmatic domains within most crystals from this sample are truncated by secondary domains associated with prominent embayments at the grain margin. Fragments of a single crystal yield contrasting, concordant dates and fragments from the edges and tips of crystals yield the youngest dates. Based on these observations we suggest that the secondary domains formed at least 26 million years after the crystal formed. Monazite and xenotime dates from the second sample, a sheared dike that cross-cuts the previous dike, spread out along concordia over 16 million years and range up to 2.4% normally discordant. Again, BSE imaging reveals secondary domains that truncate both magmatic zoning and xenocrystic cores. Fragments sliced from specific domains of a previously imaged monazite crystal demonstrate that the secondary domain is 13 million years younger than the core domain. Textures revealed in BSE images suggest that the secondary domains formed by fluid-mineral interaction. Normal discordance appears to result from both radiation damage accumulated at temperatures below 300 °C and water-mineral interaction. Monazite data from the third sample exhibit dispersion in both the ²⁰⁷Pb/²⁰⁶Pb dates (1677–1690 Ma) and discordance (+ 1.6% to − 3.1%). Reverse discordance in these monazites cannot be explained by incomplete dissolution or excess (thorogenic) ²⁰⁶Pb. Sliced fragments from several crystals reveal dramatic intragrain U-Pb disequilibrium that does not correlate with either Th or U concentration or position within the crystal. We suggest that reverse discordance resulted from mechanisms that involve exchange or fractionation of elemental U or elemental Pb, and that neither the U-Pb dates nor the ²⁰⁷Pb/²⁰⁶Pb dates are reliable indicators of the rock's crystallization age. Given the large number of processes proposed in the recent literature to explain monazite U-Pb systematics from rocks of all ages, our results can be viewed as another cautionary note for single-crystal and multi-crystal monazite geochronometry. However, we suggest that because individual crystals can preserve a temporal record of primary and secondary monazite growth, micro-sampling of individual monazite crystals may provide precise absolute ages on a variety of processes that operate during the prograde, peak and/or retrograde history of metamorphic terranes. Received: 9 June 1996 / Accepted: 18 October 1996  相似文献   

Comment on “Locating a Point on a Spherical Surface Relative to a Spherical Polygon of Arbitrary Shape” by Michael Bevis and Jean-Luc Chatelain     

Douglas M. Hawkins 《Mathematical Geology》1991,23(8):1085-1086

  相似文献   

Green and sustainable remediation practices in Federal Agency cleanup programs     

Louis E. Martino  Carol L. Dona  Jerry Dicerbo  Amy Hawkins  Beth Moore  Robert Horner 《Environmental Earth Sciences》2016,75(21):1407

  相似文献   

Field meeting at Pangbourne and Basildon: Saturday,May 11th, 1929     

H.L. Hawkins 《Proceedings of the Geologists' Association. Geologists' Association》1929,40(4):388-389

  相似文献   

Excursion to Kingsclere: Saturday,May 21st, 1927     

H.L. Hawkins 《Proceedings of the Geologists' Association. Geologists' Association》1928,39(1):98-102

  相似文献   

Field meeting at Reading: Saturday,May 4th, 1946     

H.L. Hawkins 《Proceedings of the Geologists' Association. Geologists' Association》1946,57(3):164-171

  相似文献   

An examination of the possible occurrence of sea-floor spreading magnetic anomalies on Macquarie Island     

P. Williamson  L. V. Hawkins  B. Long 《Marine Geophysical Researches》1981,5(2):139-155

Macquarie Island is composed of rocks petrologically similar to those formed at accreting ocean ridges. For this reason a geophysical study of the island and the surrounding ocean was undertaken to examine the possible presence of sea-floor spreading magnetic anomalies. The marine magnetic phase of the study allowed sea-floor spreading anomalies from the Australian plate to be fentatively correlated across Macquarie Island. Macquaric Island occurring about anomaly 7 time (27 m.y.b.p.). The palaeomagnetic phase of the study produced an apparent palaeomagnetic pole for the island consistent with the above. Modelling of the on-land magnetics indicates that the on-land magnetic data reflect dominantly the remanent magnetic properties of the rocks. Exact identification of the time-reversal sequence was not possible, however, because of distruption caused by major faulting on the island.  相似文献