The relationship between sampling intensity and sampling error-empirical results from acoustic surveys in Polish vendace lakes
Abstract The relationship between sampling effort and the variance of hydroacoustic estimates of fish abundance was studied on the basis of 17 surveys in four lakes. These differed in their morphometric and trophic characteristics, but all contained fish communities dominated by vendace ( Coregonus albula L.). Regression between the degree of coverage and the coefficient of variation was produced. The sampling error of abundance estimates was less than 10% at coverage higher than 2 for all the observations. Seasonal changes in fish spatial distribution did not affect the variability significantly. The zigzag survey design gave less variable results than regular parallel transects but the difference was not statistically significant.
In this paper we present a macro-economic demographic growth modelhaving a special focus on social security. It is designed to study the variability of responses of the system in presence of risks and uncertainties. Here we analyze the robustness of the model towards uncertainties in parameterspecifications, introduced by ARCH-M models with the incorporation ofintervention processes. The parameters varied are labor force participationrates (one of the key sources of uncertainty in the social security policydebate), and the parameters of the production function (the key source ofuncertainty in any long-run economic analysis). The sensitivity analysisfocuses on two variables: assets of the private pension system and thebalance of the public `Pay As You Go' pension system. Special attentionis given to convergence properties of the macro-economic model.