THE invasion of an alien fish in inland water, even in major rivers, has increasingly become a threat to the aquatic biodiversity. A native fish of South America, known as the suckermouth catfish originally imported as a pet fish for the household aquariums, was first sighted in open water in the early 1990s. Its presence in large number has recently been reported by fishermen in Bogura, Cumilla, Mymensingh and Noakhali. The protracted breeding period, its ability to survive in low oxygen and high toxicity in water has allowed the fish to establish a natural population. Experts consider the fish to be a major threat to aquatic lives and biodiversity as the rapid propagation of the catfish can trigger an immediate food crisis for native algivores. The invasion may eventually threaten the survival of indigenous fish varieties. Similar invasion in other countries has resulted in the extinction of local fish. The incident suggests an absence of rules and regulations in importing and cultivating wildlife specimen for commercial purposes.
While the chief scientific officer of the Bangladesh Fisheries Research Institute has sought not to consider the existence of sucker fish in open water, the fisheries department has initiated an investigation to assess the impact of the invasion on native fish population. This is, however, not the first case of invasion of alien fish in local water bodies. The farming of omnivorous African catfish and South American piranha created a similar concern earlier. The government banned the farming of African catfish in 2013, three decades after its introduction. The red piranha was banned about a decade after it had been introduced. While the ban on the farming of invasive alien species is welcome, it also highlights the absence of government foresight. A thorough aquatic biodiversity impact assessment is what is now warranted, but the government has introduced a new fish variety for commercial farming without any long-term assessment. In general, the agencies concerned are not proactive in preserving the indigenous fish varieties that are common sources of fish protein in Bangladesh. Local varieties, meanwhile, face extinction amidst the disappearance of water bodies and fast-growing hybrid fish cultivation.
Controlling invasive species can be difficult, but the best method to prevent their introduction is making policies and educating people. There is an urgent need for legislation to prevent the release of aquarium fish and potentially damaging alien species into natural water bodies. Awareness materials should be developed explaining the ecological implication of such species specifically to students, aquarium hobbyists and fish breeders. The government must also review its regulations on wildlife import.
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