Optimization of survey sampling design in the detection of interannual variability and prey size selectivity in the diet of penguins

摘要

Based on the preliminary results of a survey of prey size in Adélie penguins, sampling designs intended for the detection of inter-annual variations in mean prey size and penguin size-related selectivity were analyzed in order to find the optimal allocation of observations at each level in nested ANOVA designs. The optimal numbers of penguins and krill to be used in the detection of inter-annual variability in the parameters concerned are recommended and a required sampling protocol is suggested.A table of minimal numbers of penguins to be sampled as a function of number of sampling dates and magnitude of the variance component is given, under the assumptions of balanced design and the variance component of ‘penguin-by-date’ interaction equal to the variance component of ‘penguin-within-dates’ obtained from a previous study in Bahía Esperanza.Restrictions have been fixed in accordance with the recommendations of the fourth meeting of WG-CEMP: minimum inter-annual variation for mean prey size is fixed at 10%; the test power is taken as 0.9 and Type I errors fixed at 0.1.Cost values of manpower required are based on Argentinian logistics.