Risk assessment model for the introduction of non-native freshwater fish into New Zealand

Abstract

A risk assessment model was developed to score the potential risk for both the establishment and impact of introduced freshwater fish species in New Zealand. Although based on similar models developed for Australia and the UK, it is customised to a New Zealand context in which the risk of a site-specific ecological impact is of more concern than the potential for a species to spread rapidly and widely (i.e. its invasiveness). The model was calibrated using data on 21 introduced fish species already present in New Zealand and tested on eight species not present but for which a decision on introduction has been made using other methods. Threshold scores for risk of establishment, risk of impact and overall risk of causing ecological damage were set based on current knowledge and incorporated into a decision support system to provide managers with a numerical (vs subjective) basis for deciding on whether or not to permit the entry of a new species. The model assists in decision-making on the introduction of new species and also provides a means of assessing the ecological risk posed by the further spread of those introduced fish already present.