Updated distribution of the endangered freshwater stingray Urogymnus polylepis in Malaysia, with notes on biology and genetics

• Main Authors: Then, Amy Yee-Hui, Lim, Kean Chong, Loh, Kar Hoe
• Format: Article
• Published: National University of Singapore 2022
• Subjects: GC Oceanography; GE Environmental Sciences
• Online Access: http://eprints.um.edu.my/41289/
• Institution: Universiti Malaya

The giant freshwater stingray Urogymnus polylepis (Bleeker, 1852) (family Dasyatidae) is an endemic species in the Southeast Asian region, but comprehensive records of the distribution of this species within local river systems and their biology are still lacking. We reviewed current information for this species based on media reports, published literature as well as field observations. Two direct encounters of this species in Mukah, Sarawak, and in Sandakan, Sabah, confirmed recent occurrences of this species in Malaysian Borneo with the finding of an adult female with four pups. Public wildlife sighting information also provided additional 29 novel sightings of this species in Malaysia, out of which four were first records at the locations of Kukup and Sungai Sembrong in Johor, Pulau Bruit in Sarawak, and Tanjung Batu Laut in Sabah. These records suggested relatively high capture rates by trawlers in coastal areas and that the animals are closely associated with clean river systems. Genetic analysis showed paraphyly in U. polylepis with the formation of two major clades; one from the Gulf of Thailand and Malaysian Borneo, and the other from the Andaman Sea region and Indonesia. Threats to U. polylepis due to their own biological uniqueness, rarity of their occurrence, increasing level of river pollution, and potentially isolated populations highlight the urgent need for formal protection of the species.