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Verweise |
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Autor |
Pauly, D.; Prein, M.; Hopkins, K. D. |
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Titel |
Multiple regression analysis of aquaculture experiments based on the “extended gulland-and-holt plot”: Model derivation, data requirements and recommended procedures |
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Jahr |
1993 |
Publikation |
Iclarm Stud. Rev. |
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20 |
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13-23 |
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Schlüsselwörter |
fish-culture; freshwater-aquaculture; Oreochromis-; multivariate-analysis |
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Zusammenfassung |
A method for the multivariate analysis of fish growth in aquaculture is presented. It is derived from a linearized version of the von Bertalanffy growth function (VBGF), which, in its original form, is a bivariate regression termed the Gulland-and-Holt plot. Here, a version in form of a multiple regression equation is presented. The “extended Gulland-and-Holt plot” permits to identify and quantify the key variables controlling fish growth and permits the inclusion of these environmental and treatment variables to explain variance in growth of fish. Von Bertalanffy growth parameters K and L sub( arrow left ) are obtained, which contain the combined environmental effects on fish growth and reflect the range of culture conditions. By computing the index of growth performance ( Phi '), the obtained regression models can be used for growth prediction and decisionmaking in fish farm management and production under a wide range of environmental and management conditions. Recommendations for the design of experiments, preparation of data for analysis and actual analysis procedures are given. |
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1257 |
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Autor |
Porch, C. E. |
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Titel |
Trajectory-based approaches to estimating velocity and diffusion from tagging data |
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Zeitschrift, Artikel |
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Jahr |
1995 |
Publikation |
Fish. Bull |
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93 |
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4 |
Seiten |
694-709 |
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Schlüsselwörter |
dispersion-; migrations-; tagging-; Pisces-; swimming-; models-; dispersal-; migration- |
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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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Quartly, G. D. |
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Titel |
Altimeter repeat-track analysis -- a comparison of various algorithms for producing the mean profile |
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Zeitschrift, Artikel |
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Jahr |
1995 |
Publikation |
J. Atmos. Ocean. Technol |
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12 |
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3 |
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674-686 |
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dynamical-oceanography; remote-sensing; satellite-altimetry; sea-level-measurement; geoid-; geostrophic-transport; statistical-analysis; errors- |
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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. |
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1302 |
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Autor |
Ragen, T. J. |
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Titel |
The estimation of theoretical population levels for natural populations |
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1991 |
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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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Autor |
Sparre, P. J. |
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Titel |
The data requirements for basic fisheries bio-economics |
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1994 |
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fishery-economics; stock-assessment; economic-feasibility |
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The paper discusses the links between fish stock assessment and economics of fisheries, as perceived by a fisheries biologist. It focuses on the type and format of data required from the biological side as well as the economic side, to merge the biological and the economic methodologies into a bio-economic methodology. The biological methodology in question derives from the analytical approach, which operates with cohorts and size distributions of several stocks exploited by several fleets fishing on several fishing grounds. The economic methodology comprises costs and earnings analysis of the harvesting and the processing sectors, and computations of indicators for the economic performance of the sub-sectors. The paper is based on applications of bio-economics to tropical fisheries (targeting at shrimps). The methodology has been applied during a series of workshops and seminars organized by the Fisheries Department of FA0. The paper addresses both biologists and economists. |
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1593 |
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Autor |
Walters, C. |
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Titel |
Estimation of historical stock sizes and recruitment anomalies from relative abundance time series |
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Zeitschrift, Artikel |
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Jahr |
1995 |
Publikation |
Can. J. Fish. Aquat. Sci. J. Can. Sci. Halieut. Aquat |
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52 |
Ausgabe |
7 |
Seiten |
1523-1534 |
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stock-assessment; approximation-; anomalies-; recruitment-; abundance-; growth-; survival-; algorithms-; fishery-management; marine-fisheries |
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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. |
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1779 |
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Whitmarsh, D.; Voit, E. O.; Balthis, W. L.; Holser, R. A. |
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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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1991 |
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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 |
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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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1809 |
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Arnason, A. N.; Mills, K. H. |
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Titel |
Detection of handling mortality and its effects on Jolly-Seber estimates for mark-recapture experiments |
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Jahr |
1987 |
Publikation |
Can. J. Fish. Aquat. Sci |
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44 |
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suppl. 1 |
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64-73 |
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Fischerei, Statistik, Mathematik, Modell, Mortalität, Jolly-Seber |
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Handling mortality occurs in mark-recapture experiments if animals handled and released in a given sample have a higher mortality rate than animals that were alive but not sampled. This violates the assumption of equal survival required for forming the Jolly-Seber estimates of population abundance, survival, and recruitment. The authors show that handling mortality can produce very large biases in these estimates, and we develop a test to detect it. They investigate the power of this test and find that quite large biases can be produced at handling mortality rates that are too low to be detected. They also recommend methods to prevent handling mortality from occurring in fish sampling experiments and methods to reduce bias in the estimates. The test and the bias corrections are applied to mark-recapture data for a lake whitefish (Coregonus clupeaformis ) population and to data from simulated mark-recapture experiment. |
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Zool. Dep. Comput. Sci., Univ. Manitoba, Winnipeg, Man. R3T 2N2, Canada |
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531 |
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2330 |
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Anonymus |
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Titel |
Die Fischfauna der unteren Iller |
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1987 |
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13 |
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Fisch, Vorkommen, Donau |
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unveröffentlicht |
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nein |
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2916 |
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Autor |
McGarvey, R. |
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Titel |
An age-structured open-access fishery model |
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Zeitschrift, Artikel |
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Jahr |
1994 |
Publikation |
Can. J. Fish. Aquat. Sci |
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51 |
Ausgabe |
4 |
Seiten |
900-912 |
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Schlüsselwörter |
fischerei, Population, Mathematik, Modell, Statistik, CPUE |
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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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South Australian Res. Dev. Inst., 2 Hamra Ave., West Beach, S.A. 5024, Australia |
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525 |
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2324 |
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