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Klupp, R. (1991). Besatzversuch mit drei verschiednenen Bachforellenherkünften und einem bacheigenem Wildstamm (Vol. 1991).
Schlüsselwörter: Fisch, Fortpflanzung, Salmo trutta fario
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Käfel, G. (1991). Autökologische Untersuchungen an Misgurnus fossilis im March-Thaya Mündungsgebiet. Wien: Universität.
Schlüsselwörter: Fisch, Misgurnus
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Diercking, R., & Wehrmann, L. (1991). Artenschutzprogramm: Fische und Rundmäuler in Hamburg. Hamburg: Umweltbehörde Hamburg.
Schlüsselwörter: Fisch, Vorkommen, Verbreitung, Kartierung
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McKenna, J. E., & Saila, S. B. (1991). Application of an Objective Method for Detecting Changes in Fish Communities: Samar Sea, Philippines (Vol. 4).
Schlüsselwörter: Fischerei, statistik, Ökosystem, methode, programm, simulation
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Whitmarsh, D., Voit, E. O., Balthis, W. L., & Holser, R. A. (1991). A spreadsheet model of renewable resource exploitation – Hierarchical Monte Carlo modeling with S-distributions: Concepts and illustrative analysis of mercury contamination in king mackerel.
Zusammenfassung: Increasing numbers of students now study natural resource and environmental economics at undergraduate level, and this interest in the subject has been matched by a corresponding expansion in the number of textbooks and other learning material available for use. Unfortunately one very important aspect of natural resource economics which is often not adequately dealt with in the undergraduate literature concerns the question of dynamics: how rapidly will a resource become exploited, and what time path will it follow? These issues are particularly relevant to the management of renewable resources such as fish stocks whose survival depends on factors such as the rate of entry and exit by the exploiting firms, and the ability of the resource to recover from the effects of intense harvesting. The fault of most textbooks stems not from a failure to cover the question of dynamics, but rather that the treatment is often too advanced or mathematical for the majority of students. Computers can make a useful contribution to our understanding of the dynamics of natural resource exploitation, and in this example the case of marine commercial fishery exploited under 'open-access' conditions is considered. The quantitative assessment of environmental contaminants is a complex process. It involves nonlinear models and the characterization of variables, factors, and parameters that are distributed and dependent each other. Assessments based on point estimates are easy to perform, but since they are unreliable, Monte Carlo simulations have become a standard procedure. Simulations pose two challenges: They require the numerical characterization of parameter distributions and they do not account for dependencies between parameters. This paper offers strategies for dealing with both challenges. The first part discusses the characterization of data with the S-distribution. This distribution offers several advantages, which include simplicity of numerical analysis, flexibility in shape, and easy computation of quantiles. The second part outlines how the S-distribution can be used for hierarchical Monte Carlo simulations. In these simulations the selection of parameter values occurs sequentially, and each choice depends on the parameter values selected before. The method is illustrated with preliminary simulation analyses that are concerned with mercury contamination in king mackerel (Scomberomorus cavalla). It is demonstrated that the results of such hierarchical simulations are generally different from those of traditional Monte Carlo simulations.
Schlüsselwörter: Renewable-resources; Mathematical-models; Natural-resources; Economics-; Dynamic-analysis, Environmental-economics, Monte-Carlo-method; simulation-; numerical-analysis; mercury-; bioaccumulation-; fish-; quantitative-analysis; statistical-models; data-processing; pollution-effects; mathematical-models; scomberomorus-cavalla, S-distributions
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Sekine, M., Nakanishi, H., Ukita, M., & Murakami, S. (1991). A shallow-sea ecological model using an object-oriented programming language (Vol. 57).
Zusammenfassung: The purpose of this study is to construct a model that can predict the impact on fisheries caused by coastal development activities. To accomplish this, many species of fish must be incorporated in the model, because each type of fish has a different value as a fishery resource and a different behavior for the same impact. In addition the effect of fish swimming must be considered because even when the total resource amount of fish does not change, fish may still disappear from the object area. These factors make the model structure complicated. Meanwhile, a new concept called “object oriented programming” (OOP) is attracting the attention of modellers. In this paper, we have constructed a model called the “shallow-sea ecological model” (SSEM), by using Smalltalk, which is representative of the OOP language. This showed that the fishing ground environment are expressed very flexibly and plainly by Smalltalk.
Schlüsselwörter: Ökosystem, modell, oop, methode, theorie
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Ganguly, S., & Chaudhuri, K. (1991). A note on an extension of Schaefer's model (Vol. 55).
Zusammenfassung: Schaefer's model on the exploitation of a single species fish community obeying the logistic law of growth has been modified by adopting an alternative functional form for the harvest rate. The stability of the nontrivial steady state is discussed. The existence of a bionomic equilibrium is proved. The problem for optimal exploitation of the fishery is studied by using variational calculus. Some results are numerically computed to make a comparative study of Schaefer's model and the present one.
Schlüsselwörter: Statistik, population, modell, algorithmus
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Klein, W. (1991). “Fischlift” und “Vertical-Slot-Fischpaß” (Vol. 5).
Schlüsselwörter: Fisch, Fischaufstiegshilfe, Fischaufstiegshilfe
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