La biodiversité craint que des poissons hybrides élevés par l'homme s'intègrent dans le lac des Philippines

Hybrid fish bred for the ornamental pet trade have taken up residence in a Philippine lake, raising concerns over their impact on native biodiversity. Flowerhorn cichlids, human-bred hybrids known for their vibrant gold coloration and pronounced head humps, are believed to have escaped into Lake Sampaloc during a recent typhoon. This 104-hectare body of water, located within a volcanic crater, is already under stress from pollution and nutrient overload, making it highly susceptible to invasive species. Scientists warn that these hybrid fish may disrupt the delicate balance of the lake's ecosystem. Local fisheries rely heavily on tilapia, a hardy species that thrives in challenging conditions. However, flowerhorns share similar traits, allowing them to coexist with tilapia in aquaculture systems. Some individuals have even been captured from the wild and reintroduced into the ornamental trade, while others have been deliberately stocked by locals. Researchers from Ateneo de Manila University, Hannah Nicole C Gasmen and Dr Janice A Ragaza, have documented this integration and caution that such practices could accelerate the spread of an invasive population. Lake Sampaloc faces multiple environmental pressures, including sewage discharge, household runoff, excess nutrients from aquaculture, and plastic waste. These factors contribute to eutrophication, creating conditions that favor resilient, adaptable species like the flowerhorn cichlid. Native species such as the ayungin, or silver perch, have declined significantly and are now listed as endangered by the International Union for Conservation of Nature. Scientists attribute this decline partly to competition from invasive species. Rupert Collins, a senior curator of fish at London’s Natural History Museum, emphasized that degraded environments are particularly vulnerable to invasions by generalist species. He noted that cichlids, including flowerhorns, are adept at adapting to new conditions and can rapidly evolve new traits. This adaptability makes them a prime example of how invasive species can quickly establish themselves in altered ecosystems. Another concern involves potential health risks associated with the flowerhorns. Some captive specimens have been found carrying Paracapillaria philippinensis, a parasitic roundworm that can infect humans. Although no cases of infection have yet been reported in Lake Sampaloc’s population, researchers urge caution regarding the consumption of these fish. They recommend avoiding the promotion of flowerhorns as a food source until further studies confirm their safety. The situation in Lake Sampaloc reflects broader global challenges related to biodiversity loss. According to Collins, the introduction of non-native species beyond their natural ranges is a significant factor in the degradation of ecosystems worldwide. Dr Noël Juvigny-Khenafou, a lecturer in aquatic environmental science at the University of Stirling, added that climate change could exacerbate these issues. Shifts in temperature and precipitation patterns might influence where aquaculture operations are conducted, potentially leading to the introduction of more non-native species into new areas. Juvigny-Khenafou highlighted the complex ecological questions posed by the presence of flowerhorns. He asked whether the native species would be driven toward extinction or if the ecosystem might stabilize into a new configuration with the invasive species playing a role. Understanding these dynamics is crucial for predicting future changes in biodiversity and ecosystem functions. To address the growing threat, researchers propose several measures aimed at preventing further spread of the invasive fish. These include reinforcing aquaculture enclosures with stronger materials, using finer mesh to prevent escape, installing overflow barriers, conducting regular inspections, and engaging local communities in monitoring efforts. Additionally, there is potential for utilizing invasive fish in aquafeed, provided they undergo thorough testing for pathogens, heavy metals, and microplastics. Gasmen stressed the importance of collaboration among communities, research institutions, and policymakers to protect and sustain aquatic ecosystems. She called for a coordinated effort to manage the current crisis and prevent similar situations from arising elsewhere.