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| Autor |
Yamagishi, H.; Ishioka, K. |
| Titel |
Silumation Study on the Growth Variation of Fish with Special Reference to the Mortality by Cannibalism |
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Zeitschrift, Artikel |
| Jahr |
1991 |
Publikation |
Bull. Nansei Natl. Fish. Res. Inst. Nanseisuikenho. |
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Ausgabe |
24 |
Seiten |
163-176 |
| Schlüsselwörter |
Wachstum, mortalitÄt, simulation, methode, theorie, statistik |
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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| Rufnummer |
217 |
Signatur |
2105 |
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Whitmarsh, D.; Voit, E. O.; Balthis, W. L.; Holser, R. A. |
| Titel |
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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Buch |
| Jahr |
1991 |
Publikation |
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| Schlüsselwörter |
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 |
| Zusammenfassung |
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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Zu bestellen |
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Signatur |
1809 |
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| Autor |
Mohn, R. |
| Titel |
Length-Based Virtual Population Analysis; A Review and Swordfish Example |
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Zeitschrift, Artikel |
| Jahr |
1991 |
Publikation |
ICCAT Working Document |
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Fischerei, population, cpue, lÄngenfrequenz, wachstum, modell, statistik |
| 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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nein |
| Rufnummer |
414 |
Signatur |
2218 |
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| Autor |
Guti, G.; Andrikowics, S.; Biró, P. |
| Titel |
Nahrung von Hecht (Esox lucius), Hundsfisch (Umbra krameri), Karausche (Carassius carassius), Zwergwels (Ictalurus nebulosus) und Sonnenbarsch (Lepomis gibbosus) im Ócsa-Feuchtgebiet, Ungarn |
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Zeitschrift, Artikel |
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1991 |
Publikation |
Fischökologie |
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4 |
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Seiten |
45-66 |
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Fisch, Parasit |
| Zusammenfassung |
Ócsa bog is one of the last remnants of an ancient moorland situated between the rivers Danube and Tisza in Hungary. During the years between 1984 and 1986, the food composition of five species of fish living in the ponds and channels of a former peat mine were examined: pike (Esox lucius), mud minnow (Umbra krameri), crucian carp (Carassisu carassius), catfish (Ictalurus nebulosus) and pumpkinseed (Lepomis gibbosus). Most of the data were collected during the summer months. Overlapping food ranges of the different species were described with the Renkonen index. Much overlap was found between species Carassius carassius, Ictalurus nebulosus and Lepomis gibbosus.Das Ócsa-Feuchtgebiet liegt ca. 30 km südwestlich von Budapest, östlich des ungarischen Teils des Donautals. Ócsa ist ein Naturschutzgebiet und enthält einen der letzten und wichtigsten Reste des Marschlandes, das sich einst zwischen den Flüssen Donau und Tisza erstreckte. Die Erforschung der Vegetation dieses Gebietes begann im 19. Jahrhundert (Kerner 1867-1879)Im 20. Jahrhundert wurde das Marschland intensiv erforscht (Boros 1936, Zólyomi 1951, Komlódi 1957, Siklósi 1984). Noch heute wird das Gebiet sehr genau botanisch untersucht; nur wenige Wissenschaftler haben jedoch die Fischfauna bearbeitet. Botta et al. (1980, 1984) veröffentlichten über die Gewässer dieser Region, gaben jedoch ihr Untersuchungsgebiet nicht genau an. Andrikovics & Peer (1990) analysierten die Nahrungszusammensetzung einiger Fischarten im Ócsa-Gebiet, vor allem die von Lepomis gibbosus und Ictalurus sp. |
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Alex |
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550 |
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Ganguly, S.; Chaudhuri, K. |
| Titel |
A note on an extension of Schaefer's model |
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Zeitschrift, Artikel |
| Jahr |
1991 |
Publikation |
ECOL. MODEL. |
Kurztitel der Zeitschrift |
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55 |
Ausgabe |
1-2 |
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Statistik, population, modell, algorithmus |
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Schaefer's model on the exploitation of a single species fish community obeying the logistic law of growth has been modified by adopting an alternative functional form for the harvest rate. The stability of the nontrivial steady state is discussed. The existence of a bionomic equilibrium is proved. The problem for optimal exploitation of the fishery is studied by using variational calculus. Some results are numerically computed to make a comparative study of Schaefer's model and the present one. |
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nein |
| Rufnummer |
435 |
Signatur |
2239 |
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| Autor |
Ragen, T. J. |
| Titel |
The estimation of theoretical population levels for natural populations |
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Buch |
| Jahr |
1991 |
Publikation |
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environmental-conditions; biological-production; marine-mammals; marine-fish; population-dynamics; size-distribution; computer-programs; simulations-; frequency-analysis; migratory-species; Callorhinus-ursinus; Atractoscion-nobilis; Seriola-lalandei; Stereolepis-gigas; INE,-USA,-California; ISW,-USA,-Alaska,-St.-Paul-Island, carrying-capacity |
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The focus of this dissertation was the estimation of theoretical reference levels such as K, the environmental carrying capacity, and MNPL, the maximum net productivity level, for three fishes off Southern California and for the northern fur seal (Callorhinus ursinus) population of St. Paul Island, Alaska. The estimation techniques were based on computer modeling of historical population trends. The assessment of these theoretical reference levels for nature populations is fundamentally important to the development and testing of concepts in theoretical ecology and population dynamics. In the first study, maximum-likelihood estimates of pre-exploitation biomass were made for the white seabass (Atractoscion nobilis) and the yellowtail (Seriola lalandei) by assuming that development of corresponding commercial fisheries led to a shift in size distributions of these fishes, as indicated by records of the Avalon Tuna Club, Santa Catalina Island, California. Pre-exploitation biomass for Southern California populations of both these fishes was estimated to be about 20,000 tons. The pre-exploitation biomass of the giant sea bass (Stereolepis gigas) was estimated to be 1300 tons. Due to insufficient natural history information, this estimate was based on commercial catch records only. In the second study, estimates of theoretical reference levels for the northern fur seal population of St. Paul Island were based on computer simulations of pup production from 1912 to 1970, repetitive simulations were used to construct frequency distributions of estimates for MNPL, K, the number of pups born at MNPL and K, and the ratio MNPL/K. These distributions serve as a measure of the confidence that can be placed in single estimates of reference levels, and thereby provide a general context within which these reference levels can be evaluated. The final study of this dissertation investigated the pelagic migration of northern fur seal pups. Results indicated that initial migration paths for these pups are more widely dispersed than previously assumed. This information contributes to the understanding of northern fur seal life histories. A fuller understanding of life history information will eventually facilitate more accurate modeling of northern fur seal population dynamics. (DBO) |
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1311 |
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Sekine, M.; Nakanishi, H.; Ukita, M.; Murakami, S. |
| Titel |
A shallow-sea ecological model using an object-oriented programming language |
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Zeitschrift, Artikel |
| Jahr |
1991 |
Publikation |
ECOL. MODEL. |
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57 |
Ausgabe |
3-4 |
Seiten |
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Ökosystem, modell, oop, methode, theorie |
| Zusammenfassung |
The purpose of this study is to construct a model that can predict the impact on fisheries caused by coastal development activities. To accomplish this, many species of fish must be incorporated in the model, because each type of fish has a different value as a fishery resource and a different behavior for the same impact. In addition the effect of fish swimming must be considered because even when the total resource amount of fish does not change, fish may still disappear from the object area. These factors make the model structure complicated. Meanwhile, a new concept called “object oriented programming” (OOP) is attracting the attention of modellers. In this paper, we have constructed a model called the “shallow-sea ecological model” (SSEM), by using Smalltalk, which is representative of the OOP language. This showed that the fishing ground environment are expressed very flexibly and plainly by Smalltalk. |
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nein |
| Rufnummer |
405 |
Signatur |
2209 |
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Lepetit, M.; Loranchet, S.; Gillet, P.; Marion, J. M. |
| Titel |
Un Logiciel De Traitement Des Histogrammes De Structure De Population Par La M+Thode Des Differences Logarithmiques De Bhattachary |
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Zeitschrift, Artikel |
| Jahr |
1991 |
Publikation |
Vie Milieu |
Kurztitel der Zeitschrift |
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41 |
Ausgabe |
2/3 |
Seiten |
127-131 |
| Schlüsselwörter |
Population, statistik, programm, pascal, lÄngenfrequenz, methode |
| Zusammenfassung |
The software “BHATTA”, achieved in Turbo Pascal on IBM PC makes possible histogram analysis for population structure. The base of the study is an analysis of population dynamics from histograms of size frequency. The program “BHATTA”, made from the method of logarithmic differences of Bhattacharya, cuts the histograms in order to display Gaussian components and to estimate the parameters: number (size of sample), mean and standard deviation for each generation or cohort to determine growth curves for each cohort. |
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nein |
| Rufnummer |
400 |
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2204 |
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