The ability to predict invasive species spread is essential for effective biosecurity management and the allocation of monitoring effort. Prevention of invasive fish incursions poses a significant challenge because of the wide physiological tolerances of many species, their mobility, and the role of humans in their spread. In New Zealand, seven introduced fish species are distributed to varying extents across the two main islands. We used field data from 470 New Zealand lakes to fit models of the current distributions of these species; the resulting models were then used to predict risks of future establishment in all New Zealand lakes >1 ha.
Models using lake- and catchment-scale environmental predictors identified summer temperature amongst the two most influential variables with lake density and size also important for some species. Models for some species were improved by the addition of variables describing human population densities and lake accessibility. All seven species occurred most frequently in lakes close to human population centres implicating the importance of human-mediated dispersal.
Addition of a spatial variable, indicating the presence or absence of the modelled species within the broader catchment within which each lake is located, improved the predictive performance of models for three species. This indicates that the current distributions of these species include clusters of lakes within ‘occupied’ catchments, resulting in geographic patchiness that is independent of the available environmental and human population predictors. This distribution has most likely resulted from spread into accessible and suitable lakes from one or more initial liberations, either by natural dispersal along waterways or human-assistance.
Predictions to a broader set of 3595 New Zealand lakes indicate (i) the potential for future spread is greatest for catfish, perch and rudd, and (ii) high vulnerability to invasion for lakes along the east coast of both islands and in inland montane regions of the South Island. Our results allow for improved identification of lakes likely to be suitable for invasive fish species which should be accorded priority for surveillance, and highlight in particular the potential for perch and catfish to establish in higher elevation lakes distant from human population centres.