The imperiled fish fauna in the Nicaragua Canal zone

Abstract

Large-scale infrastructure projects commonly have strong effects on the environment. Thus, it is of highest importance to evaluate possible impacts on biodiversity and take measures to reduce these. The planned construction of the Nicaragua Canal will irreversibly alter the aquatic environment of Nicaragua in many ways. Two distinct drainage basins (San Juan and Punta Gorda) will be connected, fostering biotic homogenization due to establishment of non-native species, extirpation of local species and alteration of numerous ecosystems. Considering the far-reaching impact of this project on Nicaragua's environment, too few studies on biodiversity have been performed in affected areas. This limits the ability to make solid environmental impact assessments. Here, we explore the geographic distribution of taxonomic and genetic diversity from representative freshwater fish species across the Nicaragua Canal Zone. We show that freshwater fish faunas likely differ substantially between drainage basins (Jaccard similarity = 0.33). Further, most populations from distinct drainage basins are highly differentiated based on mitochondrial cytb. Removing the geographic barrier between these basins will promote genetic homogenization and the loss of unique diversity. Moreover, we found species in areas where they were not known to exist and provide insights into the distribution of an undescribed, highly distinct clade of livebearing fish (Poecilia). Our results indicate that the Nicaragua Canal likely will have strong impacts on Nicaragua's freshwater biodiversity. However, knowledge about the extent of these impacts remains scarce, highlighting the need for more thorough investigations to inform more cogently on the status quo before the environment is altered irreversibly.