Temperature and hydrologic alteration predict the spread of invasive Largemouth Bass (Micropterus salmoides)

The successful establishment of an aquatic invasive alien species can be mediated by a suite of environmental factors, including climate and anthropogenic disturbance. Dams and reservoirs are thought to promote freshwater fish invasion success through hydrological alterations but the evidence for their role in the global invasion of Largemouth Bass (Micropterus salmoides) on a landscape scale is limited. Here, we examine the distribution of Largemouth Bass, one of the most widely introduced fish in the world, from the Iberian Peninsula using species distribution models (SDMs), including an ensemble forecast. We used these models to test the role of twelve environmental predictors expected to influence the distribution of Largemouth Bass, including the reservoir storage capacity at local and upstream reaches. We found that the predictive accuracy, based on AUC criteria, of the ensemble model was higher than any of the six individual SDMs for Largemouth Bass. The most influential predictor of bass distribution included in our model of the Iberian Peninsula was temperature, where warmer temperatures were generally associated with bass presence, and cooler temperatures with absence. In addition to warmer temperatures, increasing storage of local and upstream reservoirs increased predicted presence, suggesting an important role of reservoirs in mediating the invasive success of this fish. Our results indicate that although natural climatic factors may be crucial in the successful invasion of Largemouth Bass, hydrological alteration (e.g., regulated flow regimes and lentic habitats associated with dams and reservoirs) may be important. Understanding the drivers promoting the establishment of this global invader will be important in identifying areas at risk and in developing future efforts to control its spread, especially when those drivers are ongoing anthropogenic disturbances such as the construction and operation of dams and reservoirs.