| Einträge |
| Autor |
McGarvey, R. |
| Titel |
An age-structured open-access fishery model |
Typ |
Zeitschrift, Artikel |
| Jahr |
1994 |
Publikation |
Can. J. Fish. Aquat. Sci. |
Kurztitel der Zeitschrift |
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| Band |
51 |
Ausgabe |
4 |
Seiten |
900-912 |
| Schlüsselwörter |
modell, statistik, population, dynamik, algorithmus |
| Zusammenfassung |
A dynamic model for open-access fisheries is presented. In addition to density dependence in recruitment and fishing effort changing in proportion to the level of profit fishermen earn which characterizes previous open-access models, it incorporates full age structure for the fish stock, lognormal environmental recruitment variability, and gear selectivity. The predator-prey cycling solution of the original Schaefer dynamic model, and subsequent open-access models, persists for these model extensions. Density dependence in recruitment induces greater global stability. Environmental recruitment variability, common in marine populations, is destabilizing in the neighborhood of the open-access equilibrium. Approximating model steady states of effort and catch by the corresponding averages from data time series underlies a new algorithm of parameter evaluation, applied here to an open-access model of the Georges Bank sea scallop (Placopecten magellanicus) fishery. |
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nein |
| Rufnummer |
469 |
Signatur |
2270 |
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| Autor |
Conway, G. R.; Glass, N. R.; Wilcox, J. C. |
| Titel |
Fitting Nonlinear Models to Biological Data by Marquardt´s Algorithm |
Typ |
Zeitschrift, Artikel |
| Jahr |
1970 |
Publikation |
Ecology |
Kurztitel der Zeitschrift |
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| Band |
51 |
Ausgabe |
3 |
Seiten |
503-507 |
| Schlüsselwörter |
marquardt, statistik, methode, nichtlinear, algorithmus |
| Zusammenfassung |
Equations describing biological phenomena frequently have parameters entering nonlinearly. A highly efficient method for detemining the values of parameters in such equations that will give the best least-squares fit to a set of data is Marquardt´s algorithm. A step-by-step derivation of the algorithm is given in terms that require only the knowledge of elementary calculus and matrix algebra. As an example, the method is used to fit the logistic equation to a set of data. |
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nein |
| Rufnummer |
471 |
Signatur |
2272 |
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| Autor |
Kenchington, E. L.; Full, W. E. |
| Titel |
Fourier analysis of sea scallop (Placopecten magellanicus) shell in determining population structure |
Typ |
Zeitschrift, Artikel |
| Jahr |
1994 |
Publikation |
Can. J. Fish. Aquat. Sci. |
Kurztitel der Zeitschrift |
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| Band |
51 |
Ausgabe |
2 |
Seiten |
348-356 |
| Schlüsselwörter |
population, fourier, statistik, methode, modell, wachstum, muscheln |
| Zusammenfassung |
Sea scallops (Placopecten magellanicus) were sampled from each of four scallop beds: the northeast peak of Georges Bank, Western Bank, St. Pierre Bank, and the Bay of Fundy near Digby, N.S. The outlines of scallop top shells were captured by video imagery using a semiautomated approach. Fourier shape descriptors were calculated and analyzed. Age and year-class effects were shown to be important factors influencing scallop shell shape. Allometric effects on Fourier harmonics also have a significant influence on shell shape in this species. Comparisons of Fourier harmonics between scallop beds separated by age and sampling year, and corrected for allometry, revealed significant differences in the majority of harmonic numbers. |
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nein |
| Rufnummer |
472 |
Signatur |
2273 |
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| Autor |
Marquardt, D. W. |
| Titel |
An algorithm for Least-Squares Estimation of Nonlinear Parameters |
Typ |
Zeitschrift, Artikel |
| Jahr |
1963 |
Publikation |
J. Soc. Indust. Appl. Math. |
Kurztitel der Zeitschrift |
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| Band |
11 |
Ausgabe |
2 |
Seiten |
431-441 |
| Schlüsselwörter |
mathematik, marquardt, nichtlinear, methode, algorithmus |
| Zusammenfassung |
The algorithm discribed shares with the gradient methods their ability to converge from an initial guess which may be outside the region of convergence of other methods. The algorithm shares with the Taylor series method the ability to close in on the converged values rapidly after the vicinity of the converged values has been reached. Thus, the method combines the best feutures of ith predecessors while avoiding their most serious limitations. |
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nein |
| Rufnummer |
473 |
Signatur |
2274 |
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| Autor |
Hradetzky, J. |
| Titel |
Ein effizientes Schätzverfahren für einige nichtlineare Regressionsmodelle |
Typ |
Zeitschrift, Artikel |
| Jahr |
1978 |
Publikation |
Mittlg. Forstl. Vers. u. Forschungsanstalt B.W. |
Kurztitel der Zeitschrift |
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Ausgabe |
91 |
Seiten |
155-161 |
| Schlüsselwörter |
mathematik, regression, methode, schätzung |
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An intrinsically linear regression model can be expressed, by suitable transformation of the variables, in the standard linear form, so that the parameters can be estimated by the OLS-method. In this way the residual sum of squares for the transformed model, but not for the original, in minimized. In this paper a weighted least squares method for avoiding these disadvantages is discussed. |
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nein |
| Rufnummer |
474 |
Signatur |
2275 |
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| Autor |
Robotham, P. W. J. |
| Titel |
Feeding habits and diet in two populations of spined loach, Cobitis taenia (L.) |
Typ |
Zeitschrift, Artikel |
| Jahr |
1977 |
Publikation |
Freshwater Biol |
Kurztitel der Zeitschrift |
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| Band |
7 |
Ausgabe |
5 |
Seiten |
469-477 |
| Schlüsselwörter |
Nahrung, fische, verhalten, populatio, saison |
| 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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nein |
| Rufnummer |
477 |
Signatur |
2278 |
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Juell, J. E.; Westerberg, H. |
| Titel |
An ultrasonic telemetric system for automatic positioning of individual fish used to track Atlantic salmon (Salmo salar L.) in a sea cage |
Typ |
Zeitschrift, Artikel |
| Jahr |
1993 |
Publikation |
Aquacult. Eng |
Kurztitel der Zeitschrift |
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| Band |
12 |
Ausgabe |
1 |
Seiten |
1-18 |
| Schlüsselwörter |
telemetrie, fische, methode, technik |
| Zusammenfassung |
A telemetric system for automatic positioning of individual fish in the vertical or horizontal plane is described. The position of a transmitter in a fish is computed from the difference in arrival time of the ultrasonic signal to a fixed array of hydrophones. Sources of error in positioning are discussed. In a preliminary study, the resolution of the system in time and space was adequate to monitor the behaviour of adult salmon in a sea cage. At moderate stocking density the salmon was swimming continually in counter-clockwise circles and diel rhythms in swimming speed, depth and path-radius were observed. With only 30 fish in the cage this stereotype behaviour broke down. Few or no visits into the feeding area during some feedings indicated a variable feeding motivation. |
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nein |
| Rufnummer |
478 |
Signatur |
2279 |
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Ward, G.; Fitzgerald, G. J. |
| Titel |
Male aggression and female mate choice in the threespine stickleback, Gsterosteus aculeatus L. |
Typ |
Zeitschrift, Artikel |
| Jahr |
1987 |
Publikation |
J. Fish. Biol. |
Kurztitel der Zeitschrift |
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Ausgabe |
30 |
Seiten |
679-690 |
| Schlüsselwörter |
Sex, Fisch, Verhalten, Saison |
| Zusammenfassung |
A laboratory study of female G. aculeatus revealed no conclusive evicence of active female mate choice on the basis of male aggression levels. However, highly aggressive males failed in 95% of all choice tests. The less aggressive ´chosen´ males where generally successful again in subsequent trials with the same female, and certain males were consistently successful with different females. Females exhibited an increased readiness to spawn at the end of the reproductive season, although the same males were usually selected again. |
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nein |
| Rufnummer |
479 |
Signatur |
2280 |
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Hagen, D. W.; Moodie, G. E. E.; Moodie, P. F. |
| Titel |
Polymorphism for breeding Colors in Gasterosteus aculeatus – Reproductive success as a Result of Convergence for Threat Display |
Typ |
Zeitschrift, Artikel |
| Jahr |
1980 |
Publikation |
Evolution |
Kurztitel der Zeitschrift |
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34 |
Ausgabe |
6 |
Seiten |
1050-1059 |
| Schlüsselwörter |
fische, verhalten, population, genetik, morphologie |
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nein |
| Rufnummer |
480 |
Signatur |
2281 |
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| Autor |
Robotham, P. W. J. |
| Titel |
Some Factors Influencing the Microdistribution of a Population of Spined Roach, Cobitis taenia L. |
Typ |
Zeitschrift, Artikel |
| Jahr |
1978 |
Publikation |
Hydrobiologia |
Kurztitel der Zeitschrift |
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| Band |
61 |
Ausgabe |
2 |
Seiten |
161-167 |
| Schlüsselwörter |
fische, wanderung, verhalten, nahrung |
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nein |
| Rufnummer |
481 |
Signatur |
2282 |
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