
Arnason, A. N., & Mills, K. H. (1987). Detection of handling mortality and its effects on JollySeber estimates for markrecapture experiments (Vol. 44).
Zusammenfassung: Handling mortality occurs in markrecapture 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 JollySeber 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 markrecapture data for a lake whitefish (Coregonus clupeaformis ) population and to data from simulated markrecapture experiment.
Schlüsselwörter: Fischerei, Statistik, Mathematik, Modell, Mortalität, JollySeber



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



Gascuel, D. (1994). [A simple adjustment method of agelength keys: Application to yellowfin tuna (Thunnus albacares) catches in the East Atlantic.] (Vol. 51).
Zusammenfassung: An adjustment method for agelength keys is presented that incorporates yearly variability in cohort abundances. The method is based on two models (one for growth and the other for standard deviations of length versus age) and involves an iterative algorithm. The algorithm rapidly converges to stable results that yield, under some conditions, maximum likelihood estimates. It is also used to estimate parameters of the length standard deviation model. The method is applied to yellowfin tuna (Thunnus albacares) catches in the eastern Atlantic from 1975 to 1989.
Schlüsselwörter: fisherymanagement; stockassessment; mathematicalmodels; growthcurves; biologicalage; length; Thunnusalbacares; AE,EastAtlantic; tunafisheries



McGarvey, R. (1994). An agestructured openaccess fishery model (Vol. 51).
Zusammenfassung: A dynamic model for openaccess 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 openaccess models, it incorporates full age structure for the fish stock, lognormal environmental recruitment variability, and gear selectivity. The predatorprey cycling solution of the original Schaefer dynamic model, and subsequent openaccess 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 openaccess 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 openaccess model of the Georges Bank sea scallop (Placopecten magellanicus) fishery.
Schlüsselwörter: fischerei, Population, Mathematik, Modell, Statistik, CPUE



Misra, R. K. (1986). Fitting and comparing several growth curves of the generalized von Bertalanffy type (Vol. 43).
Zusammenfassung: 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.
Schlüsselwörter: mathematicalmodels; growthcurves; fisherybiology; evaluation



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



Thomas, G., & Eckmann, R., Reiner. (2007). The influence of eutrophication and population biomass on common whitefish (Coregonus lavaretus) growth – the Lake Constance example revisited. Can. J. Fish. Aquat. Sci, 64, 402?410.
Schlüsselwörter: Fisch, Felchen, Coregonus lavaretus, Maräne, Biomasse, Wachstum, Alter



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



Wang, Y., Mervyn, R. T., & Somers, I. F. (1995). A maximum likelihood approach for estimating growth from tagrecapture data (Vol. 52).
Zusammenfassung: The Fabens method is commonly used to estimate growth parameters k and l in the von Bertalanffy model from tagrecapture 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 maximumlikelihood approach that takes account of individual varibility in both maimum lenth and ageattagging. ...
Schlüsselwörter: maximumlikeli, modell, captrecapt, wachstum

