The hypothesis that predation by feral cats and introduced foxes reduces population sizes of small, native vertebrates was supported by results of a predator-removal experiment at Heirisson Prong, a semi-arid site in Western Australia. The methods of control used against cats and foxes to protect native mammals reintroduced to Heirisson Prong produced three broad ‘predator zones’: a low-cat and low-fox zone, where foxes were eradicated and spotlight counts of cats declined after intensive cat control; a high-cat and low-fox zone where spotlight counts of cats increased three-fold after foxes were controlled; and a zone where numbers of cats and foxes were not manipulated. Small mammals and reptiles were monitored for one year before and three years after predator control began. Captures of small mammals increased in the low-cat and low-fox zone, but where only foxes were controlled captures of small mammals declined by 80%. In the absence of cat and fox control, captures of small mammals were variable over the sampling period, lower than where both cats and foxes were controlled, yet higher than where only foxes were controlled. The capture success of reptiles did not appear to be related to changes in predator counts. This study presents the first experimental evidence from mainland Australia that feral cats can have a negative impact on populations of small mammals.

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McAuley, R. B., Simpfendorfer, C. A., and Wright, I. W. 2007. Gillnet mesh selectivity of the sandbar shark (Carcharhinus plumbeus): implications for fisheries management. – ICES Journal of Marine Science, 64. Gillnet mesh selectivity parameters for the sandbar shark (Carcharhinus plumbeus) were estimated from catches taken by an experimental net of six panels of mesh, varying in size from 10.2 to 25.4 cm. The length selectivity of each mesh size was described by five different models. According to model deviance values, the four models based on the SELECT method of estimation provided better fits to the data than the gamma model previously applied to sharks. Lengths at maximum selectivity were estimated to be between 5.3 and 7.0×stretched mesh size. The breadth of the selectivity curves was greater than have been reported for most species of shark. Lognormal and normal curve forms yielded the lowest model deviance and were judged to provide the best fits to the data. Peak selectivity of the commercially utilized mesh sizes was generally estimated to be greater than the observed modal length class of the commercial C. plumbeus catch. This suggests that a relatively high abundance of smaller sharks in the study area offsets gear selectivity effects in determining the size composition of commercial catches. These results have important implications for the recovery of this overexploited stock and also for managing international gillnet fisheries for the species.

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