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

Based on preliminary results of prey size in Adélie penguins, sampling designs intended for detection of interannual variations in prey mean sizes and penguin size related selectivity are analysed for the optimal allocation of observations at each level in nested designs.
Recommended numbers for detection of interannual variability are obtained and a 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 variance component for penguin x date interaction equal to the variance component for penguin in dates obtained from a previous study in Bahia Esperanza.
Restrictions have been fixed accordingly with the IV meeting of CEMP: minimum interannual variation for prey mean size is fixed at 10 %; the test power is taken as 0.9 and Type I errors fixed at 0.1
Cost values are those of argentine logistics, and FORTRAN programms, developed for this work are available through authors.