Invasive vermiculated sailfin catfish (Pterygoplichthys disjunctivus) has an impact on highly valued native fish species

Invasion by armoured catfishes (Loricariidae) is a threat to native fish communities of warm, freshwater habitats. Following importation as an ornamental species, the vermiculated sailfin catfish Pterygoplichthys disjunctivus, has become established in inland waters of Bangladesh. We recorded the distribution of sailfin catfish in Bangladesh. Vermiculated sailfin catfish was recorded in 17 rivers across the majority of the country, with well-established breeding populations in four localities. We measured competition between three native carps and sailfin catfish by determining growth and survival, and by carrying out gut analysis. The competition experiment was carried out using a randomised block design in earthen ponds with similar physico-chemical parameters to freshwater habitats in Bangladesh. It demonstrated that growth and survival rate of native cyprinid fishes can be adversely impacted in the presence of sailfin catfish. In high-density catfish treatments, growth of Cirrhinus cirrhosus (bottom-feeding omnivore), Labeo rohita (midwater omnivore) and Catla catla (pelagic planktivore) was reduced by 48.4%, 21.4% and 2.4% respectively, compared to controls containing the three cyprinids but no catfish. Survival of C. cirrhosus reduced to 70% in high-density catfish treatments, compared to 100% in catfish-free ponds, with lesser effects on the other species. Low- and medium-density catfish treatments generated lesser growth and survival effects. Catfish diet remained stable across density treatments, but diet of native fishes deviated increasingly from control values as catfish density increased. This study demonstrates impacts of sailfin catfish on native fish species and the increasing distribution of sailfin catfish in Bangladesh.