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Evidence for Asian Swamp Eels as an Emerging Threat to Everglades Amphibians

Year: 2026

Type: article

Abstract: ABSTRACT As amphibian populations around the globe continue to shrink and suffer enigmatic declines, it is critical to use systematic studies to isolate causes and provide management targets for key environmental variables. We sampled the amphibian community at 30 sites dispersed across four large regions of the Everglades (FL, USA). The sites were chosen a priori to include a wide range of values for potentially important environmental gradients. We used a series of passive and active collection techniques at each site and then used model selection to determine which factors could best explain amphibian abundance and community composition. Our results show significant differences in both amphibian abundance and community composition across the four regions. Initial analyses indicated that amphibian abundance in the Everglades is correlated with nutrient levels and pH, while amphibian community composition is correlated with nutrient levels and variation between the four regions. In the midst of this project, evidence emerged that the Asian Swamp Eel, a relatively new invader of the Everglades, was decimating crayfish and small fish populations in the most southerly wetlands where it first arrived and had been spreading across some of our survey sites. Thus, while not initially structured to test this new invasive species gradient, addition of Asian Swamp Eel catch‐per‐unit‐effort data revealed that relative abundances of this novel invader replaced nutrient levels as the best predictor of both amphibian abundance and community composition. This suggests that Asian Swamp Eels are reinforcing, even exaggerating, a north–south gradient in Everglades amphibian communities that was already present due to natural variation in nutrients and water chemistry. Historical records reveal that the contemporary lack of aquatic amphibians within the Taylor Slough sub‐region of Everglades National Park is an unnatural condition, and likely the result of ecosystem collapse driven by Asian Swamp Eels. Future management in the Everglades should focus on mitigating the impact of invasive fish and limiting future human disturbance, as well as monitoring any anthropogenic shifts in nutrient levels to better understand how to restore the amphibian community of this naturally oligotrophic system.

Source: Freshwater Biology

DOI: 10.1111/fwb.70150