Identification:
Medium-sized clam; shell moderately thick, nearly rectangular with a nearly right angle at the posterior edge; deep shell cavity. The umbo region is prominent. The shell exterior is dark brown or yellowish-brown. Juveniles have transverse wrinkles and 5-6 thin green stripes extending from the umbo to the ventral edge. These features are lost in larger, mature individuals. The nacre is yellowish-white.
Biology and Ecology:
Inhabits rivers in mountainous areas, with a soft bottom substrate of mud and sand.
Distribution:
- Vietnam: Cao Bang Province (Bang River), Lang Son Province (Ky Cung River).
- Global: Endemic to Vietnam.
Value:
Of scientific and food value.
Status:
Endemic species with a very limited distribution. Before 1975, it was relatively common in the Bang River. After 1975, particularly since 1990, the population has severely declined. Surveys and interviews with local residents in the Bang River (Cao Bang) in 2000 and 2001 failed to collect any live specimens. Due to overexploitation and potentially water pollution in the Bang and Ky Cung Rivers (the Bang River is impacted by wastewater from Cao Bang town; the Ky Cung River is impacted by wastewater from coal mines), its distribution area has continuously shrunk, estimated to be less than 500 km². The population of this clam is estimated to have declined by at least 50%.
Red List Category:
EN B2a,b,e+3a,b,d
Conservation Measures:
Included in the Vietnam Red Book and the list of protected species of the Fisheries sector since before 1996. Recommendations: Prohibit the exploitation of this clam species; protect and restore water quality in the Bang River in the Cao Bang town area; treat wastewater from coal mines before discharging into the Ky Cung River. Limit sand extraction on the Bang River. Conduct research to supplement populations through artificial breeding.