Escaped flowerhorn fish threaten biodiversity and public health in Laguna, Philippines

On July 3, 2026, researchers from Ateneo de Manila University reported that escaped flowerhorn fish are threatening biodiversity and posing potential public health risks in Lake Sampaloc, San Pablo City, Laguna. Originally introduced through the aquarium trade, these invasive species have established a significant presence in the lake following their escape during a major typhoon.

Impact of Flowerhorn Cichlids on Local Ecosystem

The flowerhorn cichlid (Amphilophus spp.) is prized for its vibrant golden hue, but its introduction has led to alarming ecological consequences. According to researchers Hannah Nicole C. Gasmen and Dr. Janice A. Ragaza, the fish have become integrated into local aquaculture operations, exacerbating pressure on native species.

Notably, the native Ayungin (Leiopotherapon plumbeus), once a staple in local diets, is now rarely seen and is classified as vulnerable by the IUCN. The territorial aggression of flowerhorns enables them to monopolize breeding grounds and feeding sites, leading to a decline in native fish populations.

Health Risks Associated with Invasive Fish

Beyond ecological concerns, the presence of flowerhorns raises significant public health issues. Previous studies indicate that these fish can harbor Paracapillaria philippinensis, a zoonotic parasite that causes intestinal capillariasis, leading to severe symptoms such as abdominal pain and chronic diarrhea.

The researchers underscore that flowerhorns may serve as reservoirs for various pathogens and contaminants, necessitating further ecological and parasitological research to develop effective management strategies for this invasive species.

Proposed Management Strategies for Flowerhorn Populations

To mitigate the impact of flowerhorns, the study suggests a circular economy model that involves harvesting these fish for aquafeed, contingent upon thorough screening for parasites and contaminants. Furthermore, the Aquatic Species Invasiveness Screening Kit (AS-ISK) is recommended as a valuable tool for assessing the invasion risks of non-native freshwater fish.

Applying AS-ISK to Lake Sampaloc and other Philippine lakes may help identify potential high-risk species early, informing targeted management actions that balance ecological restoration with community livelihoods.

In conclusion, the challenges posed by invasive species like flowerhorns highlight the need for a collaborative approach among communities, researchers, and policymakers to protect aquatic ecosystems while sustaining local cultures and economies.