36 MARCH 2026 • WORLD AQUACULTURE • WWW.WAS.ORG both native and introduced taxa. Native species such as Leiopotherapon plumbeus (Ayungin), Giuris margaritacea (Bakuli), and Glossogobius spp. (Biya) persist but are increasingly outnumbered by non-native fishes like the most commercially farmed Oreochromis spp. (Tilapia) (Figure 3), ornamental fishes such as Amphilophus spp. (Flowerhorn cichlids) and Parachromis managuensis (Jaguar cichlids). Notably, Briones et al. (2016) reported significant trophic overlap between these groups, suggesting strong competition for limited resources. The presence of Flowerhorn cichlids in Lake Sampaloc raises particular concern. According to local accounts, these ornamental fishes escaped from aquaria breeding facilities during a major typhoon, and subsequent fish assemblage surveys as early as 2016 have already documented their establishment in the lake. This is corroborated by observations during the present on-the-ground survey, which revealed that Flowerhorn cichlids are not only persisting in the wild but are also being actively farmed within the lake (Figure 4). This is particularly interesting and concerning because it indicates both accidental introduction and intentional cultivation, amplifying their ecological foothold. The proliferation of Flowerhorns, facilitated by both ornamental cage escapes and local aquaculture practices, poses significant ecological risks. Their aggressive behavior and high reproductive potential threatens native ichthyofauna and destabilizes existing food web dynamics (Nasution et al., 2022). Collectively, these factors highlight the growing ecological stress on Lake Sampaloc’s native fish populations and the urgent need for integrated management strategies that address both unintentional introductions and deliberate aquaculture of invasive ornamental species. Phenotypic Plasticity and Adaptive Success of Flowerhorn Cichlids in Polluted Environments Flowerhorn hybrids show marked phenotypic plasticity, tolerating eutrophic and contaminated conditions (Nasution et al., 2022). This adaptability underscores the importance of examining pollution dynamics in Lake Sampaloc as a key ecological factor. Recent research emphasizes the mounting pollution burden within the lake, where chemical and synthetic contaminants interact with biological stressors, undermining overall ecosystem health. Dimzon et al. (2018) conducted targeted and nontargeted chemical analyses across the lakes of San Pablo City, including Lake Sampaloc, and identified a variety of trace organic pollutants, such as pharmaceuticals, plasticizers, and industrial compounds, primarily originating from untreated sewage, household runoff, and aquaculture practices. Due to the lake’s limited outflow and prolonged water retention, these contaminants continue to persist and exert chronic sublethal effects on aquatic organisms. Similarly, Natuel et al. (2023) documented the occurrence of microplastics in both rural and urban lakes of San Pablo City, including Lake Sampaloc, reporting higher concentrations in urbaninfluenced waters. These microplastic fibers and fragments, derived mainly from synthetic textiles and packaging, are likely linked to domestic wastewater and urban surface runoff. Field observations The presence of Flowerhorn cichlids in Lake Sampaloc raises particular concern. According to local accounts, these ornamental fishes escaped from aquaria breeding facilities during a major typhoon, and subsequent fish assemblage surveys as early as 2016 have already documented their establishment in the lake. This is corroborated by observations during the present on-the-ground survey, which revealed that Flowerhorn cichlids are not only persisting in the wild but are also being actively farmed within the lake. This is particularly interesting and concerning because it indicates both accidental introduction and intentional cultivation, amplifying their ecological foothold. FIGURE 3. A monument to tilapia, symbolizing the lake’s primary aquaculture species and its central role in the livelihood and culinary identity of Lake Sampaloc’s communities. Photo: H.N. Gasmen. FIGURE 4. A caretaker tending to a fish pen, showcasing a hands-on management practice. Photo: H.N. Gasmen.
RkJQdWJsaXNoZXIy MjExNDY=