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Autor Myers, R. A.; Cadigan, N. G.   
  Titel Statistical analysis of catch-at-age data with correlated errors Typ Zeitschrift, Artikel
  Jahr 1995 Publikation Can. J. Fish. Aquat. Sci. J. Can. Sci. Halieut. Aquat Kurztitel der Zeitschrift  
  Band 52 Ausgabe 6 Seiten 1265-1273  
  Schlüsselwörter Fisch, Fischerei, Statistik, Wachstum, Mortalität, VPA, Population, Mathematik, Modell  
  Zusammenfassung (down) The statistical model used is extended to estimate abundance from commercial catch-at-age data for many of the major commercial fish species in the world. The model combines commercial catch-at-age data and research survey estimates of fish abundance; extends the model to allow correlated errors among ages within a year for the survey estimates of fish abundance. Method is formulated for modeling the fishing mortality on the oldest ages of the fish caught. Estimates are obtained using maximum likelihood. The level of correlation among ages is sufficiently large to produce large biases in the standard methods for some stocks. The statistical model that includes correlated errors greatly reduces bias and increases efficiency if the correlation in the estimation error is large.  
  Adresse  
  Organisation Abschlussarbeit  
  Herausgeber Erscheinungsort Editor  
  Sprache Sprache der Zusammenfassung Originaltitel  
  Editor der Reihe Titel der Reihe Kurztitel der Reihe  
  Band der Reihe Ausgabe der Reihe Edition  
  ISSN ISBN Medium  
  Bereich Expedition Konferenz  
  Notizen Dep. Fish. Oceans, Sci. Branch, Box 5667, St. John's, NF A1C 5X1, Canada Geprüft  
  Rufnummer 528 Signatur 2327  
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Autor Wang, Y.; Mervyn, R. T.; Somers, I. F.   
  Titel A maximum likelihood approach for estimating growth from tag-recapture data Typ Zeitschrift, Artikel
  Jahr 1995 Publikation Can. J. Fish. Aquat. Sci Kurztitel der Zeitschrift  
  Band 52 Ausgabe Seiten 252-259  
  Schlüsselwörter maximum-likeli, modell, capt-recapt, wachstum  
  Zusammenfassung (down) The Fabens method is commonly used to estimate growth parameters k and l in the von Bertalanffy model from tag-recapture data. However, the Fabens method of estimation has an inherent bias when individual growht is variable. This paper present an asymptotocally unbiasses method using the maximum-likelihood approach that takes account of individual varibility in both maimum lenth and age-at-tagging. ...  
  Adresse  
  Organisation Abschlussarbeit  
  Herausgeber Erscheinungsort Editor  
  Sprache Sprache der Zusammenfassung Originaltitel  
  Editor der Reihe Titel der Reihe Kurztitel der Reihe  
  Band der Reihe Ausgabe der Reihe Edition  
  ISSN ISBN Medium  
  Bereich Expedition Konferenz  
  Notizen Geprüft nein  
  Rufnummer 463 Signatur 2264  
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Autor Borregon, J. L.; Paredes, C.; Elorza, F. J.   
  Titel New algorithms for the statistical modelling of geological heterogeneous media: Comparative results Typ Buch
  Jahr 1995 Publikation Kurztitel der Zeitschrift  
  Band Ausgabe Seiten  
  Schlüsselwörter algorithms-; statistical-analysis; heterogeneity-; radioactive-waste-disposal; geology-; simulation-; aquifers-; geochemistry-; groundwater-pollution; pollution-control; waste-disposal-sites; environmental-protection  
  Zusammenfassung (down) The characterization of an heterogeneous geological media can be approached by means of an statistical treatment of the field data. This lets us know its spatial variability behaviour, in probability terms. The algorithms presented in this work belongs to the scope of simulation of geological heterogeneous random fields. The aim of that characterization is related with the reseach studies of nuclear waste repositories in deep geological structures. Several stochastic generation algorithms are presented, based in the geostatistical regionalized variable, fractal geometry, and spectral Fourier theories. Some of them are deeply exposed here to their understanding. As a result of the paper, some comparative schemes are showed with numerical, geostatistical and spectral analysis of the implicit autorregresive generation methods.  
  Adresse  
  Organisation Abschlussarbeit  
  Herausgeber Erscheinungsort Editor  
  Sprache Sprache der Zusammenfassung Originaltitel  
  Editor der Reihe Titel der Reihe Kurztitel der Reihe  
  Band der Reihe Ausgabe der Reihe Edition 0  
  ISSN ISBN Medium  
  Bereich Expedition Konferenz  
  Notizen Zu bestellen Geprüft  
  Rufnummer Signatur 241  
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Autor Angermeier, P. L.; Smogor, R. A.   
  Titel Estimating number of species and relative abundances in stream-fish communities: Effects of sampling effort and discontinuous spatial distributions Typ Zeitschrift, Artikel
  Jahr 1995 Publikation Can. J. Fish. Aquat. Sci. J. Can. Sci. Halieut. Aquat Kurztitel der Zeitschrift  
  Band 52 Ausgabe 5 Seiten 936-949  
  Schlüsselwörter Fisch, Fließgewässer, Habitat, Verbreitung  
  Zusammenfassung (down) The authors sampled fishes and measured microhabitat in series of contiguous habitat units (riffles, runs, pools) in three Virginia streams. Monte Carlo simulations were used to construct hypothetical series of habitat units, then examined how number of species, similarity in relative abundances, and number of microhabitats accumulated with increasing number of habitat units (i.e., sampling effort). The curves indicated that 90% of the species present were usually found by sampling 5 to 14 habitat units (stream length of 22-67 stream widths). Estimates of species relative abundances required less sampling effort for a given accuracy than estimates of number of species. Rates of species accumulation (with effort) varied among streams and reflected discontinuity in species distributions among habitat units. Most discontinuity seemed to be due to low population density rather than to habitat selectivity. Results from an Illinois stream corroborated our findings from Virginia, and suggested that greater sampling effort is needed to characterize fish community structure in more homogeneous stream reaches.  
  Adresse  
  Organisation Abschlussarbeit  
  Herausgeber Erscheinungsort Editor  
  Sprache Sprache der Zusammenfassung Originaltitel  
  Editor der Reihe Titel der Reihe Kurztitel der Reihe  
  Band der Reihe Ausgabe der Reihe Edition  
  ISSN ISBN Medium  
  Bereich Expedition Konferenz  
  Notizen Natl. Biol. Serv., Virginia Coop. Fish Wildl. Res. Unit, Virginia Polytech. Inst., Blacksburg, VA 24061-0321, USA Geprüft nein  
  Rufnummer 620 Signatur 2414  
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Autor Fotland, A.; Mehl, S.; Sunnanaa, K.   
  Titel Methods of index calculation and presentation of fish abundance data using standard computer programs Typ Buch
  Jahr 1995 Publikation Kurztitel der Zeitschrift  
  Band Ausgabe Seiten  
  Schlüsselwörter fishery-management; fishery-statistics; stock-assessment  
  Zusammenfassung (down) Standard 0-group indices and distribution maps are now produced based on hand-drawn maps using AutoCad with some additional procedures. This paper briefly describes the method. The paper further describes ways of importing coastlines and survey data directly into standard computer programs such as AutoCad and SAS. Standard methods are used for gridding data, producing isolines and further calculation of abundance indices and presentation of distributions. Interactive editing of distribution maps are made, which makes corresponding automatic updating of indices possible.  
  Adresse  
  Organisation Abschlussarbeit  
  Herausgeber Erscheinungsort Editor  
  Sprache Sprache der Zusammenfassung Originaltitel  
  Editor der Reihe Titel der Reihe Kurztitel der Reihe  
  Band der Reihe Ausgabe der Reihe Edition 0  
  ISSN ISBN Medium  
  Bereich Expedition Konferenz  
  Notizen Zu bestellen Geprüft  
  Rufnummer Signatur 435  
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Autor Porch, C. E.   
  Titel Trajectory-based approaches to estimating velocity and diffusion from tagging data Typ Zeitschrift, Artikel
  Jahr 1995 Publikation Fish. Bull Kurztitel der Zeitschrift  
  Band 93 Ausgabe 4 Seiten 694-709  
  Schlüsselwörter dispersion-; migrations-; tagging-; Pisces-; swimming-; models-; dispersal-; migration-  
  Zusammenfassung (down) Several new models are developed to estimate the velocity and diffusion of a population from tagging data. The new estimators apply the inverse principle to the individual trajectories of recovered tags rather than to their local abundance. These models require fewer assumptions and less information than do published abundance-based methods. Techniques are presented for a variety of circumstances, and both discrete and continuous parameterizations of the velocity field are included. The sensitivity of the estimators to violations of the assumptions was examined numerically by using stochastic simulations. The results suggest that the estimators are fairly robust but may fail under certain conditions. Extensions to accommodate these situations are discussed.  
  Adresse  
  Organisation Abschlussarbeit  
  Herausgeber Erscheinungsort Editor  
  Sprache Sprache der Zusammenfassung Originaltitel  
  Editor der Reihe Titel der Reihe Kurztitel der Reihe  
  Band der Reihe Ausgabe der Reihe Edition  
  ISSN ISBN Medium  
  Bereich Expedition Konferenz  
  Notizen Zu bestellen Geprüft  
  Rufnummer Signatur 1295  
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Autor Quartly, G. D.   
  Titel Altimeter repeat-track analysis -- a comparison of various algorithms for producing the mean profile Typ Zeitschrift, Artikel
  Jahr 1995 Publikation J. Atmos. Ocean. Technol Kurztitel der Zeitschrift  
  Band 12 Ausgabe 3 Seiten 674-686  
  Schlüsselwörter dynamical-oceanography; remote-sensing; satellite-altimetry; sea-level-measurement; geoid-; geostrophic-transport; statistical-analysis; errors-  
  Zusammenfassung (down) Sea surface height may be measured by a satellite-borne altimeter and its along-track slope used to infer geostrophic currents. A major difficulty is that, in general, the local geoid and satellite orbit are not known to the accuracy desired. Thus, comparison is often made between repeat flights of an altimeter along fixed ground tracks in order to infer the changes in the currents. In practice, it is convenient to calculate a mean height profile from many repeat passes and use this as a reference, so that individual altimetric profiles yield variations about this mean. It is thus important to derive a high-quality reliable estimate of the altimetric mean in order to minimize the errors in the inferred flows for the individual repeats. This work examines various methods for deriving the mean profile.  
  Adresse  
  Organisation Abschlussarbeit  
  Herausgeber Erscheinungsort Editor  
  Sprache Sprache der Zusammenfassung Originaltitel  
  Editor der Reihe Titel der Reihe Kurztitel der Reihe  
  Band der Reihe Ausgabe der Reihe Edition  
  ISSN ISBN Medium  
  Bereich Expedition Konferenz  
  Notizen Zu bestellen Geprüft  
  Rufnummer Signatur 1302  
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Autor Walters, C.   
  Titel Estimation of historical stock sizes and recruitment anomalies from relative abundance time series Typ Zeitschrift, Artikel
  Jahr 1995 Publikation Can. J. Fish. Aquat. Sci. J. Can. Sci. Halieut. Aquat Kurztitel der Zeitschrift  
  Band 52 Ausgabe 7 Seiten 1523-1534  
  Schlüsselwörter stock-assessment; approximation-; anomalies-; recruitment-; abundance-; growth-; survival-; algorithms-; fishery-management; marine-fisheries  
  Zusammenfassung (down) Often only simple relative abundance time series and basic growth and (or) survival estimates are available for assessing impacts of fishing and environmental factors. Assessment then involves fitting production models to the series, while forcing the model with observed catch or effort series. A key uncertainty in this approach is how to deal with recruitment variations due to factors other than stock size. A dynamic programming algorithm can be used to compute maximum likelihood estimates of the recruitment anomaly sequence, given prior knowledge of growth parameters, the natural survival rate, and proportion of the variation in the relative abundance index that is due to abundance measurement errors.  
  Adresse  
  Organisation Abschlussarbeit  
  Herausgeber Erscheinungsort Editor  
  Sprache Sprache der Zusammenfassung Originaltitel  
  Editor der Reihe Titel der Reihe Kurztitel der Reihe  
  Band der Reihe Ausgabe der Reihe Edition  
  ISSN ISBN Medium  
  Bereich Expedition Konferenz  
  Notizen Zu bestellen Geprüft  
  Rufnummer Signatur 1779  
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Autor Magnusson, K. G.   
  Titel An overview of the multispecies VPA -- theory and applications Typ Zeitschrift, Artikel
  Jahr 1995 Publikation Rev. Fish Biol. Fish Kurztitel der Zeitschrift  
  Band 5 Ausgabe 2 Seiten 195-212  
  Schlüsselwörter vpa, statistik, modell, vergleich, fischerei  
  Zusammenfassung (down) 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.  
  Adresse  
  Organisation Abschlussarbeit  
  Herausgeber Erscheinungsort Editor  
  Sprache Sprache der Zusammenfassung Originaltitel  
  Editor der Reihe Titel der Reihe Kurztitel der Reihe  
  Band der Reihe Ausgabe der Reihe Edition  
  ISSN ISBN Medium  
  Bereich Expedition Konferenz  
  Notizen Geprüft  
  Rufnummer 498 Signatur 2298  
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Autor Chen, Y.; Jackson, D. A.   
  Titel Robust estimation of mean and variance in fisheries Typ Zeitschrift, Artikel
  Jahr 1995 Publikation Trans. Am. Fish. Soc Kurztitel der Zeitschrift  
  Band 124 Ausgabe 3 Seiten 401-412  
  Schlüsselwörter fishery-statistics; population-characteristics; statistical-analysis  
  Zusammenfassung (down) 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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  Organisation Abschlussarbeit  
  Herausgeber Erscheinungsort Editor  
  Sprache Sprache der Zusammenfassung Originaltitel  
  Editor der Reihe Titel der Reihe Kurztitel der Reihe  
  Band der Reihe Ausgabe der Reihe Edition  
  ISSN ISBN Medium  
  Bereich Expedition Konferenz  
  Notizen Geprüft  
  Rufnummer Signatur 308  
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