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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 |
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| Jahr |
1995 |
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algorithms-; statistical-analysis; heterogeneity-; radioactive-waste-disposal; geology-; simulation-; aquifers-; geochemistry-; groundwater-pollution; pollution-control; waste-disposal-sites; environmental-protection |
Zusammenfassung  |
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. |
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241 |
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| Autor |
Walters, C.; Ludwig, D. |
| Titel |
Calculation of Bayes posterior probability distributions for key population parameters |
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Zeitschrift, Artikel |
| Jahr |
1994 |
Publikation |
Can. J. Fish. Aquat. Sci |
Kurztitel der Zeitschrift |
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51 |
Ausgabe |
3 |
Seiten |
713-722 |
| Schlüsselwörter |
Fisch, Fischerei, Statistik, Population, Mathematik, CPUE, VPA, Modell |
| Zusammenfassung |
The Bayes posterior probability distribution is a powerful way to represent uncertainty in fisheries stock assessments, and can be calculated for key population and policy parameters of practically any population dynamics model. But the calculation is unwieldy when probabilities are to be assigned to a large grid of parameter combinations. The computational burden can be reduced substantially by analytically integrating over at least two “nuisance parameters” that occur in most assessment models: the observation error variance and the catchability coefficient. This simplification allows the analyst and manager to focus more easily on population parameters (stock size, slope of recruitment curve) that are of direct policy interest. |
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Fish. Cent., Univ. British Columbia, Vancouver, BC V6T 1Z4, Canada |
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527 |
Signatur |
2326 |
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| Autor |
Akamine, T. |
| Titel |
The BASIC program to analyse the polymodal frequency distribution into normal distributions with Marqualdt's method |
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Zeitschrift, Artikel |
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1984 |
Publikation |
Bull. Japan Sea Reg. Fish. Res. Lab. Nissuiken Hokoku |
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34 |
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53-60 |
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computer-programs, size-distribution, frequency-analysis, mathematical-models |
| Zusammenfassung |
The BASIC program for analysis of the polymodal frequency distribution into normal distributions is described. The algorithm of this program is Marqualdt's method. Gauss' elimination method is used to solve the simultaneous linear equations. Each parameter is scaled during calculation for faster convergence. User inputs the data and initial values of the parameters. It is adequate for convergence to set lambda = 10000 or larger. |
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63 |
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Swain, D. P.; Sinclair, A. F. |
| Titel |
Fish distribution and catchability: What is the appropriate measure of distribution? |
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Zeitschrift, Artikel |
| Jahr |
1994 |
Publikation |
Can. J. Fish. Aquat. Sci |
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51 |
Ausgabe |
5 |
Seiten |
1046-1054 |
| Schlüsselwörter |
Fisch, Statistik, Population, Fischerei, Geographisch, Mathematik, Modell |
| Zusammenfassung |
The authors show that spatially uniform changes in abundance can affect catchability given certain models for the distribution of fishing effort, but that this effect is slight compared with the effect of changes in the spatial spread of fish distribution. An index of distribution is described that depends only on spatial spread: the minimum area over which a specified percentage of the population is spread. We tested the density dependence of this index using data on Atlantic cod (Gadus morhua) in the southern Gulf of St. Lawrence. Results depended on the percentage of the population for which the index was evaluated. The area containing most (90 or 95%) of the population was density dependent, expanding as population size increased. The area of highest cod concentration (i.e., the area containing 50% of the population) did not expand significantly as population size increased. |
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Dep. Fish. and Oceans, Gulf. Fish. Cent., Box 5030, Moncton, NB E1C 9B6, Canada |
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529 |
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2328 |
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Angermeier, P. L.; Smogor, R. A. |
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Estimating number of species and relative abundances in stream-fish communities: Effects of sampling effort and discontinuous spatial distributions |
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Zeitschrift, Artikel |
| Jahr |
1995 |
Publikation |
Can. J. Fish. Aquat. Sci. J. Can. Sci. Halieut. Aquat |
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52 |
Ausgabe |
5 |
Seiten |
936-949 |
| Schlüsselwörter |
Fisch, Fließgewässer, Habitat, Verbreitung |
| Zusammenfassung |
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. |
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Natl. Biol. Serv., Virginia Coop. Fish Wildl. Res. Unit, Virginia Polytech. Inst., Blacksburg, VA 24061-0321, USA |
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nein |
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620 |
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2414 |
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Fore, L. S.; Karr, J. R.; Conquest, L. L. |
| Titel |
Statistical properties of an index of biological integrity used to evaluate water resources |
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Zeitschrift, Artikel |
| Jahr |
1994 |
Publikation |
Can. J. Fish. Aquat. Sci |
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51 |
Ausgabe |
5 |
Seiten |
1077-1087 |
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Umweltverschmutzung, Fisch, Elektrofischerei, Methode, Mathematik, Modell, Statistik, ANOVA |
| Zusammenfassung |
The authors determined the statistical properties of the index of biotic integrity (IBI) from electrofishing samples collected from Ohio streams. Although IBI is widely used to evaluate the condition of water resources by biologists and resource managers, expanding its role as a regulatory tool depends on statistical validation of its precision and power. We addressed these issues by constructing an additive variance model for IBI and testing the assumptions of that model directly with a bootstrap resampling algorithm and simulations using field data. Statistical properties of IBI supported the use of standard analysis techniques such as ANOVA for hypothesis testing. We determined with power analysis that IBI can distinguish between five and six nonoverlapping categories of biotic integrity based on a model that includes the effects of measurement error, variability of fish assemblages through time, and statistical interaction of location and time. |
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Inst. Environ. Stud., FM-12, Univ. Washington, Seattle, WA 98195, USA |
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526 |
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2325 |
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| Autor |
He, X. |
| Titel |
Effects of predation on a fish community: A whole lake experiment |
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1990 |
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predation-; interspecific-relationships; freshwater-fish; population-dynamics; Esox-lucius; Phoninus-eos; Lepomis-; Semotilus-atromaculatus; freshwater-ecology |
| Zusammenfassung |
Studies of predator-prey interactions have been limited to laboratories or relatively small scale field experiments because of logistic difficulties in large scale field experiments. Much evidence has suggested that predictions based on small scale experiments on predator-prey interactions may not be simply extended to large scales, e.g. whole system. This study was designed to examine predation effects on a prey fish assemblage at the whole lake scale. After a year of premanipulation study, northern pike (Esox lucius) were introduced into a small piscivore-free lake inhabited by 14 species of fishes. In the third and fourth years, the lake was divided by a large mesh fence and northern pike were introduced into one half of the lake. Predation effects on individual prey population were estimated for both direct effects (i.e., consumption of prey species) and indirect effects, including habitat changes associated with predator avoidance behavior, increase of emigration rates and changes of population size structure. The relative importance of direct versus indirect effects was examined using randomized intervention analysis along with a model that quantifies the indirect effects. Decreases of prey fish biomass due to increased emigration was at least as great as that due to the direct effect of consumption when prey biomass was high (>40 kg/ha) but not when prey biomass was low (<30 kg/ha). Significant indirect effects included dramatically decreased abundance of the dominant species (northern redbelly dace, Phoxinus eos), increase of some rare species (sunfish, Lepomis spp. and creek chub, Semotilus atromaculatus), and decreased mean sizes of redbelly dace. Indirect effects occurred rapidly and were most apparent immediately following the introduction of northern pike. Community responses to northern pike predation included changes of species composition, species diversity and community stabilities. The fish communities were significantly different among the pre-pike period, pike period and post-pike period. The greatest variance was related to abundances of redbelly dace and sunfish. However, predation effects on the prey fish community depended on the observational scales used to determine community structure. (DBO) |
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628 |
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Fotland, A.; Mehl, S.; Sunnanaa, K. |
| Titel |
Methods of index calculation and presentation of fish abundance data using standard computer programs |
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1995 |
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fishery-management; fishery-statistics; stock-assessment |
| Zusammenfassung |
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. |
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435 |
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Porch, C. E. |
| Titel |
Trajectory-based approaches to estimating velocity and diffusion from tagging data |
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Zeitschrift, Artikel |
| Jahr |
1995 |
Publikation |
Fish. Bull |
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93 |
Ausgabe |
4 |
Seiten |
694-709 |
| Schlüsselwörter |
dispersion-; migrations-; tagging-; Pisces-; swimming-; models-; dispersal-; migration- |
| Zusammenfassung |
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. |
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1295 |
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Speierl, T.; Hoffmann, K. H.; Klupp, R. |
| Titel |
Fischfauna und Habitatdiversität: die Auswirkungen von Renaturierungsmaßnahmen an Main und Rodach |
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Zeitschrift, Artikel |
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2002 |
Publikation |
Natur und Landschaft |
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77 |
Ausgabe |
4 |
Seiten |
161-171 |
| Schlüsselwörter |
Renaturierung, Gewässersanierung, Habitat, Wasserbau, Fisch, Main |
| Zusammenfassung |
Seit 1992 wurden im Rahmen des oekologischen Gewaesserbaus an Main und Rodach (Nordbayern) verbaute Flussstrecken renaturiert und eine natuerliche Dynamik wieder zugelassen. Der Vergleich der Fischfauna in zwei repraesentativen Renaturierungsbereichen (Rodachmuendung bei Marktzeuln, Main bei Zapfendorf) mit angrenzenden verbauten Flussabschnitten zeigte den aeusserst positiven Einfluss dieser Massnahmen. In den renaturierten Flussabschnitten wurden in allen Altersklassen (Adulte, Juvenile, Larven) mehr Arten und hoehere Individuenzahlen gefunden als in den verbauten Bereichen. Besonders ausgepraegt war dieser Unterschied bei subadulten Tieren und Fischlarven. Die renaturierten Bereiche fungieren auf Grund ihrer wiedergewonnenen Strukturvielfalt (und damit der Vielfalt an Mesohabitaten) sowohl als Laichplaetze fuer Arten mit unterschiedlichem Anspruch (Kieslaicher Krautlaicher) als auch als Refugium fuer larvale und juvenile Stadien. |
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1596 |
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