Developing empirical management procedures to meet management objectives for data-limited fisheries

Most of the world’s fish stocks are considered data-limited and there are insufficient data for complex stock assessment models; nevertheless, scientifically sound management advice is required. Empirical management procedures rely on empirical data and can guide management decisions. The main goals of this project were to develop and test empirical management procedures to improve data-limited fisheries management. Candidate management procedures can be evaluated using management strategy evaluation, which simulates the managed system and management in a feedback loop. Here, many generic operating models were generated covering a wide range of life histories. First, a trend-based empirical management procedure was explored. Simulations revealed that the management performance depended on the individual growth rate of the species, and the method delivered poor performance with high risk of stock depletion for faster-growing species. However, management performance could be improved by applying a genetic algorithm and optimisation towards specified management objectives such as long-term sustainable exploitation and risk limits demanded by stakeholders. An alternative empirical method (harvest rates) was found to be applicable to faster-growing species. Optimised parameterisations of the empirical methods from generic simulations were confirmed for several case study stocks with more available data. These analyses suggested that the generic methods lead to precautionary management, but management performance can be improved through case-specific optimisation. The outcomes of this project showed that the current management practices of data-limited fisheries resources applied by the International Council for the Exploration of the Sea in Europe are insufficient and do not ensure sustainable and precautionary exploitation, even though this is required through international treaties. However, the management procedures evaluated in this study show a way to overcome current management deficiencies and indicate that simple empirical management procedures are a scientifically sound alternative to expensive model-based management approaches.Open Acces

Correlated motion of two atoms trapped in a single mode cavity field

We study the motion of two atoms trapped at distant positions in the field of a driven standing wave high-Q optical resonator. Even without any direct atom-atom interaction the atoms are coupled through their position dependent influence on the intracavity field. For sufficiently good trapping and low cavity losses the atomic motion becomes significantly correlated and the two particles oscillate in their wells preferentially with a 90 degrees relative phase shift. The onset of correlations seriously limits cavity cooling efficiency, raising the achievable temperature to the Doppler limit. The physical origin of the correlation can be traced back to a cavity mediated cross-friction, i.e. a friction force on one particle depending on the velocity of the second particle. Choosing appropriate operating conditions allows for engineering these long range correlations. In addition this cross-friction effect can provide a basis for sympathetic cooling of distant trapped clouds.Comment: 10 pages, 9 figures, accepted for publication in Phys. Rev. A. Minor grammatical changes to previous versio

An Exploration into the Determinants of Patent Activities. Some Empirical Evidence for Austria

Series: Discussion Papers of the Institute for Economic Geography and GIScienc

Hundert Jahre für den Naturschutz

HUNDERT JAHRE FÜR DEN NATURSCHUTZ Hundert Jahre für den Naturschutz / Fischer, Helmut (Rights reserved) ( -

Telephone Communication Patterns in Austria. A Comparison of the IPFP based Graph-Theoretic and the lntramax Approaches

Two alternative methodological approaches (the IPFP based and the intramax procedures) to the problem of pattern identification in spatial interaction data are compared and evaluated in this paper. After a general discussion of the major characteristics and shortcomings of these methodologies, the paper presents the findings of a case study relying on telecommunication data measured by the Austrian PTT in 1991, in terms of erlangs. The results clearly illustrate the superiority of the intramax approach in the context of mediumsized and relatively centralised flow systems. (authors' abstract)Series: Discussion Papers of the Institute for Economic Geography and GIScienc

Interregional and International Telephone Communication Aggregate Traffic Model and Empirical Evidence for Austria

Series: Discussion Papers of the Institute for Economic Geography and GIScienc

The Role of Space in the Creation of Knowledge in Austria. An Exploratory Spatial Data Analysis

The paper makes a modest attempt to shed some light on the role of space in the creation of technological knowledge in Austria. The study is exploratory rather than explanatory in nature and based on descriptive techniques such as Moran¿s I test for spatial autocorrelation and the Moran scatterplot. Clusters of the knowledge ¿output¿ [measured in terms of patent counts] are compared with spatial concentration patterns of two input measures of knowledge production: private R&D and academic research. In addition, employment in manufacturing is utilised to capture agglomeration economies. The analysis is based on data aggregated for two digit SIC industries and at the level of Austrian political districts. It explores the extent to which knowledge spillovers are mediated by spatial proximity in Austria. A time-space comparison makes it possible to study whether divergence or convergence processes in knowledge creation have occurred in the past two decades. As in the case of any exploratory data analysis, the findings need to be treated with caution and should be viewed only as an initial pre-modelling stage in the enterprise. Future research activities will be devoted to further exploring the issue of local university knowledge spillovers within a refined production framework (see Griliches 1979). (authors' abstract)Series: Discussion Papers of the Institute for Economic Geography and GIScienc