Range expansion of invasive alien sailfin catfish Pterygoplichthys species in Sri Lanka

Abstract

South American sailfin catfish (Pterygoplichthys) popularly known as tank cleaner is one of the accidently introduced invasive fish into the natural freshwater habitats of Sri Lanka. External morphological analysis showed the presence of two Pterygoplichthys species (previously misidentified as Hypostomus plecostomus) in Sri Lankan waters, namely P. disjunctivus and P. pardalis. According to the national list on invasive alien fauna (2011), sailfin catfish was found in freshwater habitats in the Western and North western provinces of the country. This study was conducted from September 2012 to August 2013 in 76 freshwater sampling sites including canals, streams, rivers, reservoirs, marshes, flood plains in Central (CP), Eastern (EP), North-central (NCP), North-western (NWP), Sabaragamuwa (SBP), Southern (SP), Uwa (UP) and Western (WP) provinces aiming to detect and map natural range expansion of sailfin catfishes. Fish were caught using cast net and electro fishing device. Two hundred and eight fish were caught during the study and their total length ranged from 5.6–46.6cm. Sailfin catfish has increased its natural range from North western and Western provinces into Central, Eastern, North-central and Uwa provinces. Out of 76 sampling sites surveyed, 46(60%) sites had well established sailfin catfish populations. They inhabit perennial reservoirs, tanks, irrigation cannels, flood detection areas as well as rivers, streams, marshes and flood plains. The fish has shown adaptations to flourish in comparatively unpolluted environments such as perennial reservoirs (in NC province), Attanagalu Oya Upper reach (Weeragula), as well as highly polluted environments i.e. Hali Ela (in CP), Bellanwila-Attidiya marsh (in WP). It was also recorded in a brackish water cannel in Pamunugama, Gampaha, and this was the first record of occurrence of sailfin catfishes in brackish waters in the country. Sailfin catfishes were not recorded in Sabaragamuwa, Southern, Uwa, Eastern and Central provinces. Further studies to identify the factors that affect the range expansion of this invasive fish in Sri Lanka are warranted.