Non-native fish species are related to the loss of ecological integrity in Neotropical streams: a multimetric approach

Abstract

The use of multimetric indices (MMIs) became a common practice for evaluating ecological integrity of aquatic ecosystems. However, most developed MMIs ignore non-native species as an impact source to establish reference conditions. We developed an MMI to identify if non-native fish species are associated with Neotropical stream integrity by considering the presence of non-native species as an impact source. We calculated and evaluated responsiveness to the presence of non-native species using fish metrics, which were selected with a bootstrap procedure. Streams for calibration and validation were also selected with a bootstrap procedure. From the candidate MMIs generated, we selected models with different combinations of fish metrics. The generated MMIs presented a satisfactory performance in distinguishing reference streams from those impacted by non-native species. The abundance of non-native species was highly correlated with urbanization and seems to be more important than urbanization to drive native abundance loss. Our study is one of the first attempts to develop MMIs in which non-native species are considered as impact sources and used to identify impacted and reference sites. The final MMI that we developed might be a useful tool for aquatic biodiversity conservation and the development and application of non-native species control actions.