Apfelböck, H. (1995). Schneller mit 32 bit.
Schlüsselwörter: Windows, Tips, Grundlagen
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Magnusson, K. G. (1995). An overview of the multispecies VPA -- theory and applications (Vol. 5).
Zusammenfassung: Multispecies virtual population analysis is an attempt to take species interactions into account when assessing the status of fish stocks. It was introduced primarily with the aim of lowering the uncertainty in the natural mortality rate as used in single species VPA and to take account of variability between years and ages by calculating inside the model the part of the mortality rate caused by predation. The output of the MSVPA is therefore – in addition to stock sizes and fishing mortality rates as in single species VPA and intraspecific – and possible species replacement are not considered and neither is predation on larvae and prerecruits. The potential relevance of multispecies models lies in long-term forecasts since short-term forecasts from multi- and single species models differ only slightly. In making long-term forecasts, predicting recruitment is of fundamental importance and the value of MSVPA in throwing light on the processes governing recruitment is limited. MSVPA is concerned primarily with calculating postrecruitment mortalities, and although in principle there is nothing to prevent prerecruitment predation mortalities being calculated, such estimates are not likely to be reliable or useful. Predation on the larval stages can be of major importance in determining recruitment but is not addressed in the MSVPA. Thus, it is quite possible that processes which are not dealt with in the MSVPA are much more important in determining the future of the fisheries. In view of all this uncertainty, it is inevitable that it will be questioned whether multispecies management advice is superior to single species advice.
Schlüsselwörter: vpa, statistik, modell, vergleich, fischerei
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Scholtz, G. (1995). Ursprung und Evolution der Flußkrebse (Crustacae, Astacida) (Vol. 34 (N.F.)).
Schlüsselwörter: Krebs, Prähistorisch, Systematik, Entwicklungsgeschichte
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Kappus, B., Böhmer, J., & Jansen, W. (1995). Fischwanderungen im Bereich von naturnahen Aufstiegshilfen im Neckareinzugsgebiet (Vol. 2).
Schlüsselwörter: Fisch, Fischaufstiegshilfe, Wanderung
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Kästle, A., Krettek, R., & Stelzer, M. (1995). Einfluß von Renaturierungsmaßnahmen auf die Fischfauna von Mittelgebirgsbächen (Vol. 2).
Schlüsselwörter: Fisch, Renaturierung
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Matthes, U., Werner, R., & Kohla, U. (1995). Die Entwicklung der Fischpopulation der Oberweser im Hinblick auf die Reduktion der Salzbelastung (Vol. 2).
Schlüsselwörter: Fisch, Umweltbelastung, Gewässerverschmutzung
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Chen, Y., & Jackson, D. A. (1995). Robust estimation of mean and variance in fisheries (Vol. 124).
Zusammenfassung: Many fisheries data are commonly summarized by two statistics: mean and variance (or standard deviation). Because observed values are subject to various errors, which often are large and heterogeneous in fisheries studies, outliers commonly exist in the data. The existence of outliers biases estimation of the mean and variance if traditional estimation methods are used. Instead of assuming that errors in fisheries data follow a normal distribution with a constant variance, we propose that errors associated with observations for a variable may encompass a mixture of different levels of normally distributed errors. Based on concepts from a robust regression method, least median of squares, that is not sensitive to atypical observations in data, we develop a simple algorithm to estimate mean and standard deviation. We compare the proposed robust estimation approach with traditional methods and Tukey's biweight robust approach using simulated and field data. Based on simulations, we found little difference in estimated means and variances between the proposed and traditional methods when there were no outliers defined in simulated data. However, when outliers were defined in simulated data, the errors in estimation of the mean and its standard deviation were much smaller with the proposed method than were those estimated with traditional methods. Means and standard deviations estimated with the proposed method changed little, regardless of whether or not the simulated data were contaminated by atypical values. The proposed approach tended to have smaller estimation errors than did the robust biweight method. We demonstrate how the significance and interpretation of fisheries and ecological relationships may be adversely affected when outliers are present. We suggest using our proposed robust method to identify and down-weight outliers in estimating a mean and its standard deviation. One should justify deletion of the identified outliers using the knowledge about fish biology and environmental conditions independent of the variable assessed.
Schlüsselwörter: fishery-statistics; population-characteristics; statistical-analysis
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Wichowski, F. J., Kästle, A., & Stelzer, M. (1995). Über den Einfluß von Renaturierungsmaßnahmen auf das Makrozoobenthon und die Ichthyofauna eines Mittelgebirgsbaches (Vol. 24).
Schlüsselwörter: Renaturierung, Fisch
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Gaumert, T. (1995). Fischfauna der Elbe von der Quelle bis zur Mündung: Aktuelle Befunde im Vergleich zu alten Daten.
Schlüsselwörter: Fisch, Historisch, Elbe
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Riehl, R., Arnold, A., & Patzner, R. (1995). Die Eier heimischer Fische: 10. Moderlieschen – Leucaspius delineatus (Heckel, 1843)(Cyprinidae) (Vol. 3).
Schlüsselwörter: Fisch, Ei, Fortpflanzung, Moderlieschen, Leucaspius delineatus
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