Salinity drives abundance and distribution of an invasive estuarine fish in an arid inland river system

Abstract

Salinization of freshwater ecosystems is negatively impacting native biodiversity in arid regions around the world, increasing the risk of invasion by marine and estuarine species. In the study reported here, we investigated environmental factors, particularly salinity, regulating the abundance and morphology of an invasive estuarine species, Gulf Killifish Fundulus grandis, in the Pecos River, Texas, USA affected by anthropogenic salinization. An analysis of 20 physical, chemical, and biotic variables indicates that salinity was the only factor significantly related to F. grandis abundance. Fundulus grandis was more abundant and made up a greater percentage of the fish assemblage at moderate to high salinity levels of between 5.2 and 12. Salinity did not significantly affect F. grandis body shape or meristic traits. Morphometric analysis revealed variation in F. grandis shape related to total length and sex, with an interaction between length and sex. Males tended to be more robust than females at a given size, and body depth increased with total length. Low salinity limits the distribution of F. grandis and promotes higher native fish diversity in the Pecos River. The salinity preference of F. grandis, coupled with temporal increases in salinity from anthropogenic activity, likely contributed to the invasion success of F. grandis, including its range expansion, and increased abundance in the Pecos River. Protection of freshwater springs is essential to mitigating the impacts of F. grandis and maintaining native biodiversity.