A comparison of geostatistical and random sample survey analyses of Antarctic krill acoustic data

Data from the acoustic surveys of MV SA "Aghulas" and FRV "Walter Herwig", and the 1981 RRS "John Biscoe" South Georgia acoustic survey were analyzed by geostatistical methods. Estimates of mean density (g m-2) of krill and their variances are compared with published results (Trathan et al., 1993 and Murphy et al., 1991) from statistical analyses based on random sampling theory. A further high-resolution geostatistical analysis of the MV SA "Aghulas" (ping-by-ping) data set of the density of each individual aggregation is also presented. These analyses illustrate the problems of applying geostatistical methods to data from highly aggregated species which can show marked skewness in their histogram of density.