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Autor |
Robotham, P. W. J. |
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Titel |
Feeding habits and diet in two populations of spined loach, Cobitis taenia (L.) |
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Jahr |
1977 |
Publikation |
Freshwater Biol |
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7 |
Ausgabe |
5 |
Seiten |
469-477 |
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Schlüsselwörter |
Nahrung, fische, verhalten, populatio, saison |
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Zusammenfassung  |
The feeding habits of C.taenia were studied by means of monthly samples taken over a 2-year period, October 1972-October 1974, from two sites, one on the River Great Ouse at Newport Pagnell and the other at some neighbouring gravel pits. Dietary components, seasonal variation in these components, and seasonal and diurnal variation in feeding intensity were examined. The ecological niche of the food items and their size range are discussed, since both these factors appeared important in governing the microhabitat of the fish. The feeding activity followed a seasonal cycle with little or no feeding in the winter and a high level of feeding activity in mid-summer. The diet showed a predominance of small food items, such as chydorids, copepods and rhizopods. These items varied in occurrence during the feeding period which appeared to be related to their own abundance, pointing to non-selective feeding by the fish. The small size and benthic habits of the food items, many of which are closely associated with surface layers of mud and weed, indicated a preference by C.taenia (L.) for feeding in this type of habitat and on this type of food, in contrast to the stone loach, Noemacheilus barbatulus (L.), which is believed to inhabit stony areas and take larger food items. |
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477 |
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2278 |
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Wang, Y.; Mervyn, R. T.; Somers, I. F. |
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A maximum likelihood approach for estimating growth from tag-recapture data |
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Jahr |
1995 |
Publikation |
Can. J. Fish. Aquat. Sci |
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52 |
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252-259 |
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Schlüsselwörter |
maximum-likeli, modell, capt-recapt, wachstum |
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Zusammenfassung |
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. ... |
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463 |
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2264 |
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Schenekar, Tamara; Sturm, Sarah; Weiss, Steven J. |
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Auf den Spuren der Äsche im Gesäuse: Nachweis und Kartierung von Thymallus thymallus in der Enns und dem Johnsbach mittels eDNA |
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2019 |
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Österreichs Fischerei |
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72 |
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11/12 |
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296-309 |
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Fisch, Äsche, Thymallus thymallus, Genetik, eDNA, Nachweis, Vorkommen, Methode |
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The Enns River runs through the Gesäuse National Park and is generally characterized by relatively pristine morphological features. During the late 1990s the fish densities of this stretch collapsed, including the dominant species of this river zone, the European grayling. River restoration efforts have been undertaken to improve habitat quality and connectivity of the Enns River but also its largest tributary in the Gesäuse, the Johnsbach River, which had been heavily alternd for flood protection. However, due to intense sediment transport in the Johnsbach River, the newly built ground sills might still pose barriers for fish migrating from the Enns into the Johnsbach River. To check whether grayling enter the Johnsbach for spawning and whether these sills are passable for grayling during their migrations, we took environmental DNA samples from both the Enns River and the Johnsbach River and applied a qPCR protocol originally developed for Arctic grayling. We received positive signals of European grayling in the Enns River, as well as the Johnsbach River but only during the spring spawning season. This suggests that at least a few grayling individuals manage to pass the sills and migrate into the Johnsbach River to attempt to spawn. |
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nein |
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3085 |
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Misra, R. K. |
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Titel |
Fitting and comparing several growth curves of the generalized von Bertalanffy type |
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1986 |
Publikation |
Can. J. Fish. Aquat. Sci |
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43 |
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8 |
Seiten |
1656-1659 |
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mathematical-models; growth-curves; fishery-biology; evaluation- |
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The earlier version of the von Bertalanffy growth formula (VBGF) has three parameters and is a special case of the “generalized” VBGF which has four parameters. The special VBGF can easily lead to erroneous results whereas the large flexibility built into the generalized VBGF enables it to provide a biologically realistic fit to the data. The author presents a statistical method and a computer program in Fortran to fit the generalized VBGF to a sample (a sample comprises several age groups, with one or more observations in an age group) and to examine statistically the fit to a sample and to compare statistically these curves (and their individual parameters) fitted to several samples. An example is provided, which also compares the fit of the generalized VBGF with the special VBGF. |
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1116 |
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Baltzly, M.; Hendrickson, D. A. |
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Titel |
The new Desert Fishes Council World Wide Web server on Internet |
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0 |
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deserts-; freshwater-fish; computers-; conferences-, World-Wide-Web; internet- |
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The Desert Fishes Council has moved into the world of electronic publishing on the Internet. Dr. John Rinne (U.S. Forest Service, Flagstaff, Arizona) has allowed the first author to scan his well-known collection of fish photographs into digital format. They have been variously cropped and enhanced, and can now be viewed in different formats or downloaded by anyone in the world with Internet access. The second author is converting the Proceedings (staring with Vol. 24 [1992 meeting]) to hypertext format, so they may be browsed, searched or downloaded. All future DFC Proceedings will be published on WWW at the same time final hard copy is sent to the printer. The World Wide Web (WWW) allows anyone who has obtained free, public domain client software (readily available on Internet), primarily one called Mosaic, to browse effortlessly through multimedia files (graphics, video, sound, formatted text) that are stored on computers around the globe. Multimedia presentations can combine real-time sound, graphics and video with text. Exploration of WWW and the DFC system using Mosaic is facilitated by hypertext links, which offer the simplicity of “point and click” movement through the “cyberspace” of WWW. The Texas Memorial Museum of the University of Texas at Austin is providing storage space for these large DFC files at no charge as a pilot project for other WWW projects at UT, and can likely continue to provide this service for the forseeable future if it receives the usage and growth are predicted. All DFC members are encouraged to provide additional text, graphics and other files for inclusion in the system. Growth of the Internet has been phenomenal, and as more and more people throughout the world obtain access to it, these electronic files will allow DFC to better reach a far larger audience than was formerly possible. DFC members and others using materials provided here will be better equipped to educate the public regarding the plight of desert fishes. The system should also improve communications among ourselves and with others regarding fish conservation efforts throughout the world, and eventually should lead to reduced costs of publishing the Proceedings. |
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Zu bestellen |
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131 |
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Borregon, J. L.; Paredes, C.; Elorza, F. J. |
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Titel |
New algorithms for the statistical modelling of geological heterogeneous media: Comparative results |
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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 |
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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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Walters, C.; Ludwig, D. |
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Calculation of Bayes posterior probability distributions for key population parameters |
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Zeitschrift, Artikel |
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1994 |
Publikation |
Can. J. Fish. Aquat. Sci |
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51 |
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3 |
Seiten |
713-722 |
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Fisch, Fischerei, Statistik, Population, Mathematik, CPUE, VPA, Modell |
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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 |
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2326 |
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Akamine, T. |
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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 |
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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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Terceiro, M.; Fournier, D. A.; Sibert, J. R. |
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Comparative Performance of MULTIFAN and Shepherd_s Length Composition Analysis (SRLCA) on Simulated Length-Frequency Distributions |
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Zeitschrift, Artikel |
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Jahr |
1992 |
Publikation |
Transactions of the American Fisheries Society |
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121 |
Ausgabe |
5 |
Seiten |
667-677 |
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Schlüsselwörter |
Statistik, modell, lÄngenfrequenz, wachstum |
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Zusammenfassung |
The authors simulated length-frequency distributions for 3-, 7-, and 13-age-class exploited populations (Peprilus triacanthus, Gadus morhua, Paralichthys dentatus, Pomatomus saltatrix ) to compare the performance of Shepherd's length composition analysis (SRLCA) and MULTIFAN in resolving the distributions to age frequencies. The length distributions were characterized by von Bertalanffy growth, variable recruitment, variable mortality, partial selectivity of fishing gear for the youngest age-groups, and a length-dependent trend in the standard deviation in length at age. Comparative performance of SRLCA and MULTIFAN was assessed quantitatively by using the Kolmogorov-Smirnov cumulative distribution test to compare calculated proportions at age with the simulated values. Shepherd's analysis provided a good return for the amount of computational resources invested, with limited subjective user input. In contrast, MULTIFAN offered a much more complex but powerful estimation technique, and performed consistently better than SRLCA in matching the simulated proportions at age. |
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449 |
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2253 |
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Swain, D. P.; Sinclair, A. F. |
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Fish distribution and catchability: What is the appropriate measure of distribution? |
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Zeitschrift, Artikel |
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1994 |
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Can. J. Fish. Aquat. Sci |
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51 |
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5 |
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1046-1054 |
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Fisch, Statistik, Population, Fischerei, Geographisch, Mathematik, Modell |
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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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