Invasive poeciliids dominate fish community in a highly altered river: insights from a diversity study of riverbank fishes in Mexico

Abstract

The presence of invasive species can cause significant changes in native communities and ecosystem functions. Mexico is home to 6% of all known freshwater fish species on the planet, with a high rate of endemism. Due to heavy urbanization, the Mexican Central Plateau has become one of the most densely populated areas in the world, and its Tula River is considered one of the most polluted rivers in Mexico. Our objective was to investigate whether native fish species persist in such adverse conditions and to evaluate the seasonal and spatial distribution of both native and non-native species at three sites along the Tula River. We evaluated environmental characteristics and fish community structure. We found two native species, the black fin goodea (Goodea atripinnis) and the yellow shiner (Notropis calientis). However, their abundance was extremely low across all sites and seasons. In contrast, invasive poecilids dominated the communities, accounting for 99.4% of the total abundance. Our results indicate a clear relationship between river characteristics and fish community structure, highlighting the significance of river width, river velocity, temperature, dissolved oxygen, and pH. The prevalence of invasive species underscores the urgent need for conservation efforts aimed to protect and restore native fish populations.