Quantifying and predicting impacts of nonnative freshwater fishes in peninsular Florida, USA

Understanding the impacts of non-native species on the environment, economics, and society is critical for management and policy decision-making. Generalizing impacts across taxa and regions is a daunting task due to the complexity and range of effects, the interaction of invasive species impacts with other environmental stressors, and the differing human perceptions of effects and of costs and benefits. Despite these complexities, general frameworks for quantification of ecological impacts of non-natives have been proposed. We modified the Generic Impact Scoring System (GISS) to more adequately assess nonnative fish impacts to Peninsular Florida and applied it to assess the impacts of 32 nonnative freshwater fishes that have successfully established in the region. We also used life history traits of the species to predict level of impact and identify traits that may be associated with more severe impacts to peninsular Florida. Results suggest that overall, nonnative fishes in peninsular Florida have relatively low impacts compared with other regions. Less than 20% of fishes assessed had moderate impact GISS scores and none of the assessed species had scores indicating high impact. We found that species with higher impact scores tended to have lower swim factors, higher parental care, and a more benthic position in the water column. These analyses will be useful for managers as they work to understand the impacts of species established in Florida, and potential impacts of species yet to establish.