Identification:
- Large mussel, up to 25 cm in length.
- Thick shell, dark brown exterior.
- Interior with a nacreous layer of white, pink, or copper color; the wing and tail have a golden sheen.
- Low umbo with numerous concentric wrinkles.
- Thin wings, highly developed towards the dorsal side.
- A prominent ridge along the posterior dorsal area.
- Juveniles have thin, yellowish-green shells with many green radial lines.
Biology and Ecology:
- Inhabits rivers in the midland and lowland regions of northern Vietnam.
- Reproduces in spring and early summer. Mature females contain approximately 500-10,000 eggs.
- Larvae develop in about 15-20 days, drifting in the water before settling to the muddy bottom and developing into adult mussels.
- Feeds by filter-feeding through the siphon, retaining particulate matter and organisms from the water.
- Migrates to deeper waters during the cold season.
- Lamprotula species are common in the sandy-mud bottoms of rivers and lakes in the northern Vietnamese lowlands.
- Adapted to summer and winter weather conditions.
Distribution:
- In Vietnam: Bac Giang, Bac Ninh, Ha Tay, Hanoi, Ninh Binh.
- Worldwide: China (Central and South China).
Value:
- Valuable for scientific research on mollusks in the river and lake systems of Vietnam.
- Shells are raw material for the processing of paper pulp used in painting, beautiful nacre used in inlay crafts, and making buttons.
- Cultured for pearl cultivation in freshwater environments.
Status:
- Before 1975, common in the rivers of the northern delta; density was about 2-3 individuals per m² of the bottom.
- Annually, in the Bac Giang (Thuong River), Ha Tay, Ha Nam, Ninh Binh (Day River) regions, approximately 25-30 tons of shell were exploited.
- After 1975, especially from 1990 onwards, due to the strong development of crafts utilizing shells, the annual exploitation increased, significantly reducing the population, possibly by up to 20%.
- Pearl cultivation began in 1995 and has shown some results.
- The distribution area before 1975 extended across the entire northern delta, up to 15,000 km².
- Currently, due to intense exploitation and pollution in the rivers of the delta and midlands, the area has shrunk to about 2,000 km², and the population fluctuates greatly from year to year depending on exploitation.
Classification:
- VU (Vulnerable)
- B2a,b,e+3a,d.
Conservation Measures:
- Listed in the Vietnam Red Book and the list of species needing protection by the Fisheries sector before 1996.
- Recommendations:
- Reduce exploitation intensity.
- Exploit during non-breeding seasons.
- Implement rotational exploitation of locations.
- Prevent water pollution in the key habitats of the species.
- Conduct research to supplement the population using artificial methods.