Estimates of g(0) for minke schools from the results of the Independent Observer experiment on the 1985/86 and 1986/87 IWC/IDCR Antarctic assessment cruises

Independent observer (IO) experiment results from the 1985/86 and 1986/87 Antarctic cruises are analysed using 2 different methods. The first method (PGHR) using a hazard-rate form for g(y), and the total number of duplicate sightings, provides Balaenoptera acutorostrata school g(0) estimates for the barrel and IOP combined that are generally close to 1 (average 0.9). The other method (DNE) based on the distribution of duplicate sightings with y, produces rather lower values (average 0.63 for Shonans), and suggests a paucity of duplicates close to and an excess far from the trackline compared to what might be expected according to the models usually assumed. Results of the DNE method are tentatively preferred, as the PGHR method predicts y-distributions of duplicate sightings that are at variance with observations. -from Authors