The influence of animal mobility on the assumption of uniform distances in aerial line-transect surveys

Line-transect distance sampling is a widely used method for estimating animal density from aerial surveys. Analysis of line-transect distance data usually relies on a requirement that the statistical distribution of distances of animal groups from the transect line is uniform. We show that this requirement is satisfied by the survey design if all other assumptions of distance sampling hold, but it can be violated by consistent survey problems such as responsive movement of the animals towards or away from the observer. We hypothesise that problems with the uniform requirement are unlikely to be encountered for immobile taxa, but might become substantial for species of high mobility. We test evidence for non-uniformity using double-observer distance data from two aerial surveys of five species with a spectrum of mobility capabilities and tendencies. No clear evidence against uniformity was found for crabeater seals or emperor penguins on the pack-ice in East Antarctica, while minor non-uniformity consistent with responsive movement up to 30 m was found for Adelie penguins. Strong evidence of either non-uniformity or a failure of the capture-recapture validating method was found for eastern grey kangaroos and red kangaroos in Queensland.

Early season replacement for Imperial Mandarin CT09014

Imperial mandarin is the dominant variety in the early season production time slot in Australia. It is well known to consumers, wholesalers and supermarkets, and growers continue to make new plantings of this variety. Despite this popularity, Imperial has major faults that cause problems for growers, consumers, and at other points along the supply chain. Fruit of the variety can be severely granulated, and this is the main quality problem cited by consumers. A second problem with Imperial is its unsuitability for export. Thirdly, the variety has low juice and sugar content, and develops poor colour under warm conditions. We propose a hybridisation project to specifically address these industry obstacles.