Koi carp – a high-risk alien species. (Photo: NIWA)
The risk posed by alien fish to our freshwater species and habitats can now be evaluated using a model developed by NIWA scientists. The Freshwater Fish Risk Assessment Model (FRAM) assesses the risk of new alien fish species becoming established in New Zealand, and, importantly, their capacity to damage the environment, giving an overall ‘ecological risk’.
FRAM is powerful and simple to use. A series of straight forward questions about the biology and behaviour of any alien species lead to it being ranked and categorised as a high, intermediate, or low ecological risk. This indicates, for example, whether a proposed aquarium introduction is likely to meet an outright ‘no’ from the authorities, or the level of environmental impact assessment that may be needed.
FRAM can also be used to help prioritise conservation activities. The model has ranked all 21 existing alien species in NZ’s freshwater in terms of their ecological risk. Perch, koi carp, and catfish score highest, followed by gambusia, brown and rainbow trout, and rudd. Goldfish and tench, in contrast, are ranked low, as they pose little ecological threat.