Status Assessment of Clarias Species in the Philippines: Insights from DNA Barcodes

Catfishes of the genus Clarias are important food fishes in aquaculture. In the Philippines, six species are documented but only three, namely C. batrachus, C. macrocephalus, and C. gariepinus, are found in the market today. Of these, C. macrocephalus is both native and near threatened. In this study, the cytochrome c oxidase I (COI) gene was amplified for 20 Agusan Marsh, Agusan del Sur specimens provisionally identif ied as C. macrocephalus. These specimens have a different morphology compared to other C. macrocephalus specimens previously obtained elsewhere. The COI sequences all matched the Philippine COI sequences of C. macrocephalus, thus confirming its identity. Reanalysis of barcode sequences was also conducted to resolve the conflicting claims regarding the status of some Clarias species. A total of 179 COI sequences from Clarias species present in GenBank were included in the analyses. The average intraspecif ic and interspecif ic Kimura-2-Parameter distances were 2.99% and 13.26%, respectively. There was very little sequence diversity observed in the Philippine samples of C. macrocephalus. Philippine samples of C. batrachus and C. macrocephalus formed distinct clades, while Philippine C. gariepinus specimens clustered with those of other countries, supporting the claim that the former two species are native and the latter was introduced to the country. The status of the other Clarias species in the Philippines is also discussed