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Autor |
Chen, Y.; Jackson, D. A. |
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Titel |
Robust estimation of mean and variance in fisheries |
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Zeitschrift, Artikel |
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Jahr |
1995 |
Publikation |
Trans. Am. Fish. Soc |
Kurztitel der Zeitschrift |
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124 |
Ausgabe |
3 |
Seiten |
401-412 |
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Schlüsselwörter |
fishery-statistics; population-characteristics; statistical-analysis |
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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. |
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308 |
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Autor |
Akamine, T.; Kishino, H.; Hiramatsu, K. |
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Titel |
Non-biased interval estimation of Leslie's removal method |
Typ |
Zeitschrift, Artikel |
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Jahr |
1992 |
Publikation |
Bull. Japan Sea Natl. Fish. Res. Inst. Nissuiken Hokoku |
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42 |
Seiten |
25-39 |
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Schlüsselwörter |
Fisch, statistik, modell, binominal, population, basic, listing |
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Zusammenfassung |
Leslie's removal method, which is used to estimate the initial population size and the removal ratio simultaneously, is modeled in terms of the product of binomial distributions. The approximation of these binomial distributions to the standard normal distribution presents a new method which has no bias for estimators. This is an improvement over the maximum likelihood method and the likelihood ratio test, and is essentially equivalent to a standard goodness-of-fit test. The confidence region on the 2-dimensional plane defined by the initial population size and the removal ratio gives each confidence interval. This region is defined by the chi-square distribution with 2 degrees of freedom. |
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452 |
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2256 |
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Akamine, T. |
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Titel |
An interval estimation of Leslie's method in removal methods |
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1990 |
Publikation |
Bull. Japan Sea Natl. Fish. Res. Inst. Nissuiken Hokoku |
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40 |
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27-49 |
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Schlüsselwörter |
Fisch, statistik, binominal, population, basic, listing, modell, methode |
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Zusammenfassung |
Leslie's method in removal methods is modeled into the joint of the binomial distributions. An interval estimation of p (removal ratio) and n (initial population size) based on the null hypothesis for p and n is easily obtained by the approximation of each binomial distribution to the normal distribution. The confidence region on the (p, n) plane is easily obtained by micro-computers. The maximum likelihood method for a point estimation and the convenient method on the curves of partial maximum likelihood for an interval estimation are also presented. |
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Rufnummer |
451 |
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2255 |
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Autor |
Castro, M.; Erzini, K. |
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Titel |
Comparison of two length-frequency based packages for estimating growth and mortality parameters using simulated samples with varying recruitment patterns |
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Zeitschrift, Artikel |
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Jahr |
1988 |
Publikation |
FISH. BULL. |
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86 |
Ausgabe |
4 |
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Methode, wachstum, mortalitÄt, lÄngenfrequenz, vergleich, statistik, fisch |
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Length-frequency distributions were simulated for species with recruitment patterns characteristic of many tropical fish: 1) one recruitment peak per year, fast growth and very high mortality, 2) one recruitment peak per year, slow growth and moderate to high mortality 3) two recruitment peaks per year, slow growth and moderate to high mortality, and 4) random recruitment, slow growth and moderate to high mortality. Two microcomputer program packages – one incorporating the ELEFAN I & II programs and the other implementing a form of Modal Progression Analysis – were used to estimate growth and mortality parameters, and these were compared with the initial parameters used to generate the simulated samples. The results, while generally encouraging, suggest that multiple recruitments per year make it difficult to estimate growth and mortality parameters using these two packages. |
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nein |
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Rufnummer |
188 |
Signatur |
2077 |
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Autor |
Mohn, R. |
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Titel |
Length-Based Virtual Population Analysis; A Review and Swordfish Example |
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Zeitschrift, Artikel |
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Jahr |
1991 |
Publikation |
ICCAT Working Document |
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Fischerei, population, cpue, lÄngenfrequenz, wachstum, modell, statistik |
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Zusammenfassung |
Length-based population analyses have had a fairly long but not too successful history. These methods are required over a range of situations from when aging is impossible to when it is difficult or prohibitively expensive. There have been 3 sorts of approaches: 1) modal analysis to convert length frequencies to ages 2) age-length key enhancement and 3) imbedded growth models. The last group is what is generally known as length-based methods and the focus of this review. At the 1991 ICES Methods Working Group, 5 techniques were compared and these results are summarized. Two of these techniques, cohort slicing and length-based ADAPT, are applied to swordfish (Xiphias gladius ) data. The imbedded growth model for the former technique is the mean size at age while the latter uses the distribution of size at age. A new method is also presented which begins with cohort slicing then estimates numbers at age and enhances an inferred age-length key at each step of an iterative process. |
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Rufnummer |
414 |
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2218 |
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Hasenbein, Matthias |
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Titel |
Population ecology and growth traits of signal crayfish Pacifastacus leniusculus |
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Report |
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2010 |
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61 |
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Krebs, Signalkrebs, Pacifstacus leniusculus, Markierung, Wachstum |
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Zusammenfassung |
Invasive Arten stellen eine der Hauptbedrohungen für die Süßwasserbiodiversität dar. Die genauen Auswirkungen eines Neozoen wie dem Signalkrebs Pacifastacus leniusculus sind sehr schwer zu abzuschätzen, weil der Erfolg oder das Scheitern einer Invasion von verschiedenen Faktoren wie der Biologie der Art, Abundanz, Zeit und den Habitatbedingungen abhängig ist und daher in jedem Flusssystem einen unterschiedlichen Verlauf. In dieser Studie wurde die Populationsökologie und die Wachstumsmerkmale des Signalkrebses Pacifastacus leniusculus untersucht und ein Zwei-Jahresvergleich für 2008 und 2009 durchgeführt.
Es wurde über einen Zeitraum von 13 Wochen eine Fang-Wiederfang-Studie entlang
eines 400m langen Flussabschnitts der Moosach (Donau-Einzugsgebiet) durchgeführt.
Carapaxlänge, Gewicht, Geschlechterverhältnis, Catch per Unit Effort, Populationsgröße, Wiederfangrate und Freilandwachstum sowie Jahreswachstum wurden analysiert. Um die Wachstumsmerkmale genauer zu untersuchen, wurde in einem Laborversuch mit größensortierten Tiere Daten für den Zuwachs pro Häutung, prozentualen Zuwachs pro Häutung und die Tageswachstumsrate erhoben.
Die ermittelte Populationsdichte betrug 0,49 Individuen pro m2 und die geschätzte
Populationsgröße war 2453 Individuen. Das Geschlechterverhältnis ergab einen Wert von 1, 18 : 1 (Männchen : Weibchen). Die Wiederfangrate wies einen Wert von 11, 13% auf. Der Mittelwert für die Carapaxlänge war 51, 46mm (SD = 7, 90). Die Männchen waren im Durchschnitt schwerer als die Weibchen (Gewicht Männchen: 45, 92 g (SD = 21, 11); Gewicht Weibchen: 36, 45 g (SD = 13, 73)) und auch größer (Carapaxlänge Männchen: 52, 71mm (SD = 8, 20); Carapaxlänge Weibchen 49, 99mm (SD = 7, 26).
Die Analyse des Wachstums ergab einen durchschnittlichen Zuwachs pro Häutung für die Carapaxlänge bei den Männchen von 3, 73mm und für die Weibchen von 2, 92mm. Der
Zuwachs pro Häutung bezüglich des Gewichts betrug für die Männchen durchschnittlich
7, 02 g und für dieWeibchen durchschnittlich 3, 86 g. Der prozentuale Zuwachs pro Häutung für die Carapaxlänge war im Mittel für Männchen 7, 87% und für Weibchen 6, 55%. Der prozentuale Zuwachs pro Häutung bezüglich des Gewichts war im Mittel für Männchen 21, 59% und für Weibchen 14, 89%.
Die Ergebnisse dieser Studie zeigen, dass das Wachstum von vielen Faktoren abhängt, die eng mit der Populationsstruktur und den Habitatbedingungen in Verbindung stehen. Das Wachstum folgt nicht einem strikt vorgegebenen Prozess der von Geburt an vorherbestimmt ist, sondern ist von Fluss zu Fluss unterschiedlich und einzigartig für jedes Habitat. Daher muss die Invasion des Signalkrebses Pacifastacus leniusculus für jedes einzelne Flusssystem separat bestimmt werden und es kann nicht von einer allgemeingültigen Untersuchung auf andere geschlossen werden. |
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Master Abschluss |
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2934 |
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Autor |
Lewy, P. |
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Titel |
Integrated stochastic virtual population analysis. Estimates and their precision of fishing mortalities and stock sizes for the North Sea whiting stock |
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1986 |
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17 |
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biomass-; fishing-mortality; length-weight-relationships; Merlangius-merlangus; statistical-sampling; ANE,-North-Sea; computer-programs |
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Zusammenfassung |
Integrated Stochastic Virtual Population Analysis (ISVPA) is a method by which fishing mortality and stock size are estimated using standard statistical techniques. The estimation procedure has been programmed in FORTRAN 77 for a VAX 11/750. The dataset for North Sea Whiting (Merlangius merlangus ) presented to the North Sea Roundfish Assessment Working Group have been used to illustrate the ISVPA method. |
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ICES |
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COPENHAGEN, DENMARK |
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1013 |
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Whitmarsh, D.; Voit, E. O.; Balthis, W. L.; Holser, R. A. |
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A spreadsheet model of renewable resource exploitation – Hierarchical Monte Carlo modeling with S-distributions: Concepts and illustrative analysis of mercury contamination in king mackerel |
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1991 |
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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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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. |
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1809 |
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Autor |
Tan, Xiaobo; Kim, Drew; Usher, Nathan; Laboy, Dan; Jackson, Joel; Kapetanovic, Azra; Rapai, Jason; Sabadus, Beniamin; Zhou, Xin |
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An Autonomous Robotic Fish for Mobile Sensing |
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Conference Article |
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2006 |
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Proceedings of the 2006 IEEE/RSJ International Conference on Intelligent Robots and Systems |
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5424-5429 |
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Technik, Roboter, GPS, Umweltdaten |
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In this paper an innovative approach to robotics education is reported, where hands-on learning is integrated with cutting-edge research in the development of an autonomous, biomimetic robotic fish. The project aims to develop an energy-efficient, noiseless, untethered swimming robot for mobile sensing purposes. The robot is propelled by an ionic polymer-metal composite (IPMC) actuator and equipped with a GPS receiver, a ZigBee wireless communication module, a microcontroller, and a temperature sensor for autonomous navigation, control, and sensing. The two phases of the development are described, emphasizing both the technical approaches and the learning paradigms. The developed robotic fish will be further used as an educational kit for K-12 students and as a research tool for investigating multi-robot collaborative sensing. |
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2974 |
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| Permalink für diesen Eintrag |
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Autor |
Yamagishi, H.; Ishioka, K. |
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Titel |
Silumation Study on the Growth Variation of Fish with Special Reference to the Mortality by Cannibalism |
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Zeitschrift, Artikel |
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Jahr |
1991 |
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Bull. Nansei Natl. Fish. Res. Inst. Nanseisuikenho. |
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24 |
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163-176 |
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Wachstum, mortalitÄt, simulation, methode, theorie, statistik |
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Zusammenfassung |
In respect to the higher initial mortality in fish by cannibalism, computer simulation of individual growth variation was made in terms of coefficient of variation(CV) and skewness(sk) of frequency distribution. CV of the cannibalistic groups changed similarly to the control groups, but converged on smaller values than the asymptotic CV of the control groups. Sk of the cannibalistic groups finally converged on similar values to those of the control groups after irregular changes in positive values except N-N correspondent type. |
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2105 |
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