3 th Australasian Vertebrate Pest Conference RISK ASSESSMENT FOR THE IMPORT AND KEEPING OF EXOTIC VERTEBRATES

ABSTRACT: An analysis of historical records of the exotic birds, mammals and finfish introduced to Australia shows that several factors distinguish between species that successfully established wild populations and those that failed. For example, for all three taxa a good climate match to Australia, a large overseas geographic range and a history of successfully establishing exotic populations overseas are correlated with successful establishment in Australia. These factors are used to develop more quantitative models to assess the risk of establishment. The number of introduction events is also strongly correlated with establishment success for all three taxa. This means that if more exotic animals are kept in more places, they are more likely to establish wild populations. Although too few exotic reptiles and amphibians have been introduced to Australia to enable comparable analyses to be conducted, adequate sample sizes exist for the USA and Britain. These data are being analysed to see if the same factors are correlated with establishment success for these taxa. Our decision models are more quantitative, more transparent and more scientifically based than processes previously used by government agencies to conduct risk assessments on exotic vertebrates. However, the models still contain qualitative components requiring subjective expert judgements, so they are potentially subject to bias. Because of these subjective components, and because of the potentially expensive environmental and economic consequences of a wrong decision, we strongly recommend that those who conduct risk assessments using the models have appropriate expertise and are also independent and unbiased, with no vested interest in the outcome. INTRODUCTION Many exotic vertebrates have established wild populations on mainland Australia: 25 mammals, 20 birds, 4 reptiles, 1 amphibian and 31 finfish. An additional 7 birds, 1 rodent and 2 reptiles have established on offshore islands. Many of these species are now major pests, costing Australia $100s of millions in lost agricultural production and land and water degradation, and many threaten our native species by habitat destruction, competition and predation. Eradication of newly established exotic vertebrates has rarely been attempted and even more rarely achieved. Red-eared sliders (Trachemys scripta -a species of freshwater tortoise) have recently established exotic populations in Australia. Exotic fish species are establishing at an increasing rate Risk assessment involves identifying hazardous events (in this case the establishment of new exotic vertebrate pest species in Australia) and estimating the likelihood that such events will occur and the probable consequences if they do. Is it possible to identify exotic species that pose a high risk of establishing wild populations if they are released or escape? Many ecologists claim scientific theory and knowledge is still far from the stage where it is possible to make certain predictions about introduction success for individual species METHODS We have conducted quantitative analyses of past introductions of exotic birds, mammals and freshwater fish to Australia RESULTS This paper brings together the findings of several published and unpublished studies on risk assessment modelling for exotic vertebrates. The general findings from our analyses are presented here with selected examples of the results of our data analyses. More comprehensive details of our results are available in our referenced publications Establishment success Five key factors are correlated with establishment success: 19