The anguillid eels found in Peninsular Malaysia were identified using a morphological analysis and that identification was further validated as Anguilla bengalensis bengalensis and Anguilla bicolor bicolor by an analysis of the eels' mitochondrial cytochrome oxidase subunit I (COI) sequences. Because of the difficulty of accurately identifying tropical eels solely on morphological analyses, previous studies had reported the occurrence of the tropical eel species Anguilla marmorata in Peninsular Malaysia. This study suggests the occurrence of Anguilla bengalensis bengalensis in Malaysian waters, confirmed by both morphological and molecular genetic analyses. Anguilla bicolor is further confirmed as the subspecies of Anguilla bicolor bicolor by molecular genetic analyses. The present study also suggests that accurate tropical eel species identification requires validation by molecular genetic analysis after a morphological observation.

Previous studies indicated that a tropical mottled eel Anguilla marmorata Quoy & Gaimard, 1824 had been found in Peninsular Malaysia. After reexamination of a number of key characters of a preserved specimen, the species was identified as Anguilla bengalensis bengalensis Gray, 1831. This is the first record of the occurrence of this species in Malaysian waters. There was no eel aquaculture around the eel habitats. Thus, A. bengalensis bengalensis is a native eel species in Malaysia. The new record is suggestive of an offshore spawning area and migration route to the Malaysian coast.