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Francis, R. I. C. C. (1990). Back-calculation of fish length: A critical review (Vol. 36).
Zusammenfassung: A review is made of the literature on the back-calculation of fish body length from marks on scales or other hard parts (otoliths, vertebrae, fin rays, etc.). Though the technique is widely used it does not appear to be well understood. Regression methods are commonly used, apparently in ignorance of the more realistic proportional methods. It is not generally recognized that there are two equally plausible back-calculation hypotheses which can lead to significantly different back-calculated lengths. The Fraser-Lee equation, the most commonly used back-calculated formula, follows neither of these hypotheses but is based on a misuse of linear regression. It is recommended that back-calculation be restricted to procedures following one of the proportional hypotheses; that the difference between lengths calculated using the two hypotheses is a useful measure of the minimum uncertainty in back-calculation lengths; and that more attention be paid to validating back-calculation hypotheses by comparing observed and back-calculated lengths for individual fish. The pattern of heteroscedasticity in body length-scale radius plots is noted as a useful diagnostic in evaluating back-calculation hypothesis.
Schlüsselwörter: Fisch, Statistik, Regression, Längen..., Review, Wachstum
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Swain, D. P., & Sinclair, A. F. (1994). Fish distribution and catchability: What is the appropriate measure of distribution? (Vol. 51).
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.
Schlüsselwörter: Fisch, Statistik, Population, Fischerei, Geographisch, Mathematik, Modell
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Myers, R. A., & Cadigan, N. G. (1995). Statistical analysis of catch-at-age data with correlated errors (Vol. 52).
Zusammenfassung: The statistical model used is extended to estimate abundance from commercial catch-at-age data for many of the major commercial fish species in the world. The model combines commercial catch-at-age data and research survey estimates of fish abundance; extends the model to allow correlated errors among ages within a year for the survey estimates of fish abundance. Method is formulated for modeling the fishing mortality on the oldest ages of the fish caught. Estimates are obtained using maximum likelihood. The level of correlation among ages is sufficiently large to produce large biases in the standard methods for some stocks. The statistical model that includes correlated errors greatly reduces bias and increases efficiency if the correlation in the estimation error is large.
Schlüsselwörter: Fisch, Fischerei, Statistik, Wachstum, Mortalität, VPA, Population, Mathematik, Modell
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Walters, C., & Ludwig, D. (1994). Calculation of Bayes posterior probability distributions for key population parameters (Vol. 51).
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.
Schlüsselwörter: Fisch, Fischerei, Statistik, Population, Mathematik, CPUE, VPA, Modell
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Fore, L. S., Karr, J. R., & Conquest, L. L. (1994). Statistical properties of an index of biological integrity used to evaluate water resources (Vol. 51).
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.
Schlüsselwörter: Umweltverschmutzung, Fisch, Elektrofischerei, Methode, Mathematik, Modell, Statistik, ANOVA
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McGarvey, R. (1994). An age-structured open-access fishery model (Vol. 51).
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.
Schlüsselwörter: fischerei, Population, Mathematik, Modell, Statistik, CPUE
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Wang, Y. G., & Thomas, M. R. (1995). Accounting for individual variability in the von Bertalanffy growth model (Vol. 52).
Zusammenfassung: Estimation of von Bertalanffy growth parameters has received considerable attention in fisheries research. Since Sainsbury much of this research effort has centered on accounting for individual variability in the growth parameters. In this paper we demonstrate that, in analysis of tagging data, Sainsbury's method and its derivatives do not, in general, satisfactorily account for individual variability in growth, leading to inconsistent parameter estimates (the bias does not tend to zero as sample size increases to infinity). The bias arises because these methods do not use appropriate conditional expectations as a basis for estimation.
Schlüsselwörter: Fisch, Statistik, Methode, Vergleich, Wachstum, Bertalanffy, Faben
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Paller, M. H. (1995). Interreplicate Variance and Statistical Power of Electrofishing Data from Low-Gradient Streams in the Southeastern United States (Vol. 15).
Schlüsselwörter: fischerei, statistik, CPUE, methode, elektrofischerei, modell
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Paller, M. H. (1995). Relationships among Number of Fisch Species Sampled, Reach Length Surveyed, and Sampling Effort in South Carolina Coastal Plain Streams (Vol. 15).
Schlüsselwörter: fischerei, Statistik, population, artenzusammensetzung, methode, modell, vergleich, elektrofischerei
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Paller, M. H. (1994). Relationships between Fish Assemblage Structure and Stream Order in South Carolina Coastal Plain Streams (Vol. 123).
Schlüsselwörter: elektrofischerei, fischerei, statistik, artenzusammensetzung, modell, vergleich
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