Tropical fish community does not recover 45 years after predator introduction

Area of Science:

• Ecology
• Invasive Species Biology
• Conservation Biology

Background:

• Predation is a key factor structuring ecological communities, but its long-term impacts on diversity, especially in tropical systems, are challenging to assess.
• Biological introductions offer unique opportunities to study sustained predation effects when pre-introduction data exist.
• Zaret and Paine's 1970 study documented immediate community impacts of peacock bass (Cichla monoculus) introduction in Lake Gatun, Panama.

Purpose of the Study:

• To investigate the long-term (45-year) consequences of peacock bass introduction on the littoral fish community in Lake Gatun.
• To compare fish communities in lakes with and without peacock bass to assess the predator's sustained impact.
• To re-evaluate the ecological effects of an invasive apex predator in a diverse tropical ecosystem.

Main Methods:

• Replicated historical sampling methods in Lake Gatun to assess changes in the littoral fish community 45 years post-introduction.
• Conducted a spatial analysis comparing fish communities in two lakes with peacock bass (Gatun, Alajuela) and one without (Bayano).
• Analyzed changes in native fish abundance, diversity (rarefied species richness), and the prevalence of specific prey families (Characidae, Peociliidae).

Main Results:

• Peacock bass remains the dominant predator in Lake Gatun, with native littoral fish abundance 96% lower than pre-introduction levels.
• Species diversity declined by 64% post-introduction, with evidence of local extirpations.
• Native fish abundance was 5-40 times lower in invaded lakes (Gatun, Alajuela) compared to the uninvaded lake (Bayano), particularly for small-bodied prey species.

Conclusions:

• The profound negative effects of peacock bass on the Lake Gatun fish community have persisted for at least 45 years.
• Introduced predators can cause long-lasting alterations to community structure and diversity, even in highly diverse tropical environments.
• While overall diversity may not differ significantly, specific native species face severe declines, highlighting the persistent impact of invasive predators.