Towards a sustainable economy for the Shetland Islands: Development and management issues in fishing and fish farming

Shetland, as an isolated group of islands on the north-west margin of Europe, has always depended in its economy on marine-based resources, and current trends suggest that this will continue for the future. Up to the oil era Shetland depended mainly on the fisheries around it, although for centuries externally-based fishermen have profited more from these fisheries than have the Shetland people. As well as the development of oil from the 1970s there has been the other major economic innovation of fish farming. The oil industry is on massive scale and has greatly changed the economy of the islands and brought notable social benefits; but the direct employment it provides is considerably exceeded by the fish-related industries, which include employment in fish processing and packing plants as well as in fish catching and fish farming. With the oil industry in Shetland now on a settled downward trajectory, the islands are inevitably now having to look more to fish-related employment for their future. In the internal structure of Shetland, fish farming has a notable effect in distributing employment throughout the islands. Activity in fishing and fish processing is more selectively located: fishing is mainly concentrated in certain islands in the archipelago, particularly Whalsay and Burra; and fish processing is mainly in central locations, especially Lerwick and Scalloway. A prominent problem for fish processors is getting reliable supplies in face of higher fish prices at markets on the Scottish mainland. The processors also now face the challenge of putting more value added on their products in an outlying location. For the future there is a major issue in getting more effective measures for conservation of fish stocks in the Shetland area; there is also the related issue of whether Shetland fishermen should get preference in the allocation of fish quotas in this area. For fish farming there is the basic issue of maintaining a pollution-free environment: this was emphasised by the oil spill from the Braer oil tanker, and there is also concern about potential polluution from the prospective development of oil fields in the more difficult deep-water environment to the west of the islands.     

Exclusive rights to fish: Towards a rational fisheries policy

Discusses the tragedy of the commons with regard to fish resources in the North Atlantic, and points to the fact that the Atlantic cod has now been so heavily exploited that a strong regulation of fisheries is needed to preserve an exploitable stock. The author argues for exclusive economic zones dividing up the remaining loopholes among coastal nations and individually transferable quotas.     

Croatia as a Danube country

Among the three principal regional units of Croatia, i.e. the elongated and spacious Adriatic littoral (with numerous islands), the relatively small and narrow mountainous belt (the Croatian transit doorway) and the Pannonian/peri-Pannonian region, the latter is the largest and accounts for 54 percent of the surface area and 66 percent of the population of Croatia (1991 census). It is part of the Pannonian (or Carpathian) basin, or the central Danube basin, so that Croatia is simply by its position a Danube country. Its Danube character is also highlighted by the fact that the Pannonian/peri-Pannonian region of Croatia through the Sava and Drava Rivers is directly linked to the navigable Danube, which is the historical and ethnic eastern boundary of Croatia. Croatia is an old historical Danube nation and country, although it has nominally appeared as a state after the break-up of Yugoslavia, and its international recognition as an independent state (1992).     

Hierarchical decomposition of variance with applications in environmental mapping based on satellite images

A quadtree-based image segmentation procedure (HQ) is presented to map complex environmental conditions. It applies a hierarchical nested analysis of variance within the framework of multiresolution wavelet approximation. The procedure leads to an optimal solution for determining mapping units based on spatial variability with constraints on the arrangement and shape of the units. Linkages to geostatisiics are pointed out, but the HQ decomposition algorithm does not require any homogeneity criteria. The computer implementation can be parameterized by either the number of required mapping units or the maximum within-unit variance, or it can provide a spectrum of significances of nested ANOVA. The detailed mathematical background and methodology is illustrated by a salt-affected grassland mapping study (Hortobágy, Hungary), where heterogeneous environmental characteristics have been sampled and predicted based on remotely sensed images using these principles.     

Bayesian estimation of seismic hazard for two sites in Switzerland

Seismic hazard analysis is based on data and models, which both are imprecise and uncertain. Especially the interpretation of historical information into earthquake parameters, e.g. earthquake size and location, yields ambiguous and imprecise data. Models based on probability distributions have been developed in order to quantify and represent these uncertainties. Nevertheless, the majority of the procedures applied in seismic hazard assessment do not take into account these uncertainties, nor do they show the variance of the results. Therefore, a procedure based on Bayesian statistics was developed to estimate return periods for different ground motion intensities (MSK scale).Bayesian techniques provide a mathematical model to estimate the distribution of random variables in presence of uncertainties. The developed method estimates the probability distribution of the number of occurrences in a Poisson process described by the parameter . The input data are the historical occurrences of intensities for a particular site, represented by a discrete probability distribution for each earthquake. The calculation of these historical occurrences requires a careful preparation of all input parameters, i.e. a modelling of their uncertainties. The obtained results show that the variance of the recurrence rate is smaller in regions with higher seismic activity than in less active regions. It can also be demonstrated that long return periods cannot be estimated with confidence, because the time period of observation is too short. This indicates that the long return periods obtained by seismic source methods only reflects the delineated seismic sources and the chosen earthquake size distribution law.     

Total ozone variations in the tropical belt: An application for quality of ground based measurements

Summary The study of the regime of ozone variations in the huge tropical belt (25° S to 25° N), which are, in general, very small and zonally nearly symmetric, permits to establish a statistical model for estimating the ozone deviations using Total Ozone Mapping Spectrometer (TOMS) data. The equatorial stratospheric winds at 25 and 50hPa and the solar flux at 10.7 cm are used as major predictors and the linear trend was also estimated. The 10m/sec stratospheric wind change is related to1.2% ozone change at the equator, to practically no change in the 8–15° belts and up to 1.4% change with opposite phase over the tropics in spring but nearly zero change in fall. The solar cycle related amplitude is about 1.4% per 100 units of 10.7 cm solar flux. The ozone trends are negative: not significant over the equator and about –2% per decade (significant at 95% level) over the tropics. The latter could have been enforced by the 2 to 4% lower ozone values during 1991–1993, part of which might be related to the effects of the Mt. Pinatubo eruption, but might also be due to the strong QBO. The estimated deviations are verified versus reliable observations and the very good agreement permits applying the model for quantitative quality control of the reported ozone data from previous years. The standard deviation of the difference between observed ozone deviations and those estimated from the model is only 0.9–1.6% for yearly mean, that means instruments used for total ozone observations in the tropical belt should have systematic error of less than 1%. Cases when the discrepancies between the model and reported observations at a given station exceed 2–3% for time interval of 2 or more years should be verified.With 17 Figures     

Objective measures of the information density of satellite data

Summary We propose and objective method whereby the density of Shannon's information associated with the retrieval of a profile of atmospheric variables from satellite-derived infrared radiance measurements may be estimated. The technique is a natural extension of one we previously proposed to estimate the effective data density in a profile. We test the method in a comparison of simulated satellite instruments to show that the method does indeed provide an objective summary of the spatial distribution of each instrument's information content. We propose that further extensions of the method be developed to include other more traditional data sources in a fully three-dimensional scheme. We also note that analogous and compatible methods may be used to diagnose the information content of meteorological analysis and forecast fields relative to the information contained in the covariance, at the appropriate season, of the corresponding climate fields.With 8 Figures     

Crystal-Mush Compaction and the Origin of Pegmatitic Segregation Sheets in a Thick Flood-Basalt Flow in the Mesozoic Hartford Basin, Connecticut

Where the Holyoke flood-basalt flow in the Mesozoic HartfordBasin in Connecticut is thick and contains coarse-grained, horizontalsegregation sheets in its central part, the lower part of theflow is strongly depleted in incompatible elements; where theflow is thin and contains no segregation sheets it is homogeneousthroughout. This chemical variation can be explained only throughcompaction of the partly crystallized basalt. The compositionof the segregation sheets shows that they separated from thebasalt following only 33% crystallization. The segregation sheets,however, are clearly intrusive into the basalt, which must thereforehave already formed a crystal mush with finite strength at thislow degree of crystallinity. The incompatible element concentrationsindicate that the partly crystallized basalt underwent as muchas 28% compaction in the lowest 60 m of the flow. Between 60and 130 m above the base of the flow, the crystal mush becamedilated, and eventually ruptured with formation of the segregationsheets. No segregation sheet has a composition indicating separationafter more than 33% crystallization of the basalt. This is interpretedto indicate that compaction ceased at this stage because ofthe increasing strength of the mush and the increasing densityof the fractionating interstitial liquid KEY WORDS: crystal-mush compaction; segregation shtets; flood basalt; tholeiitie; Connecticut ^*e-mail: philpotts{at}geol.uconn.edu     

Quantification of the effects of secondary matrix on the analysis of sandstone composition, and a petrographic-chemical technique for retrieving original framework grain modes of altered sandstones

Most studies of sandstone provenance involve modal analysis of framework grains using techniques that exclude the fine-grained breakdown products of labile mineral grains and rock fragments, usually termed secondary matrix or pseudomatrix. However, the data presented here demonstrate that, when the proportion of pseudomatrix in a sandstone exceeds 10%, standard petrographic analysis can lead to incorrect provenance interpretation. Petrographic schemes for provenance analysis such as QFL and QFR should not therefore be applied to sandstones containing more than 10% secondary matrix. Pseudomatrix is commonly abundant in sandstones, and this is therefore a problem for provenance analysis. The difficulty can be alleviated by the use of whole-rock chemistry in addition to petrographic analysis. Combination of chemical and point-count data permits the construction of normative compositions that approximate original framework grain compositions. Provenance analysis is also complicated in many cases by fundamental compositional alteration during weathering and transport. Many sandstones, particularly shallow marine deposits, have undergone vigorous reworking, which may destroy unstable mineral grains and rock fragments. In such cases it may not be possible to retrieve provenance information by either petrographic or chemical means. Because of this, pseudomatrix-rich sandstones should be routinely included in chemical-petrological provenance analysis. Because of the many factors, both pre- and post-depositional, that operate to increase the compositional maturity of sandstones, petrologic studies must include a complete inventory of matrix proportions, grain size and sorting parameters, and an assessment of depositional setting.     

Revised chemical models of ζ Oph based on HST data

Hubble Space Telescope observations by Savage, Cardelli and Sofia (1992) and Cardelliet al. (1993) have led to improved gas phase abundances for many elements in the diffuse cloud towards the star Oph. Most remarkably, it was found that oxygen is much more strongly depleted than previousCopernicus observations indicated. As a consequence, chemical models of the Oph cloud are severely affected by the drop in the observed oxygen abundance by almost a factor of two; some previous model calculations for the Oph cloud failed to reproduce-even approximately-the observed high CO column density. The model calculations for the Oph cloud developed by Wagenblast (1992) in which the abundance of all observed neutral molecules could be reproduced have been revised and it is found that oxygen and nitrogen hydrides are required to be formed efficiently on the surface of grains; further, there are indications for a high cosmic ray ionization rate of the order 10^–16 s^–1.