Long-term contamination by non-native fish assemblages in a Neotropical floodplain

Area of Science:

• Ecology
• Invasive Species Biology
• Conservation Biology

Background:

• Biological invasions pose a significant threat to biodiversity, particularly in species-rich areas like the Neotropics.
• Understanding the long-term establishment of non-native fish is crucial for aquatic ecosystem management.

Purpose of the Study:

• To quantify non-native fish pressure on biodiversity in the Paraná River floodplain from 2000 to 2017.
• To analyze temporal trends in native and non-native fish assemblages and their relationship with environmental factors.

Main Methods:

• Association of fish biomass, species richness, and non-native proportion (contamination and Kempton's indices).
• Sampling in spatio-temporal gradients across lakes and rivers.
• Analysis of temporal trends using linear regressions and generalized additive models.

Main Results:

• Fish biomass increased for both native and non-native species, but their Kempton indices showed an inverse correlation.
• Native species experienced local extinction, with non-native species differentiating and contributing to ecosystem contamination.
• A consistent rise in fish biomass led to non-native species dominating the biodiversity by the end of the study period.

Conclusions:

• Non-native fish species are outcompeting and replacing native species in the Paraná River floodplain.
• Native biotic resistance was insufficient to prevent the establishment and dominance of invasive fish.
• Findings align with previous research on biotic homogenization and species extinction due to invasions and habitat alterations.