LocationsWritten by: Nguyen Thi Xuan Thang (UNDP), Nguyen Van Hieu (RIMF), Hoang Thanh Vinh (UNDP), Hoang Van Chung (RIMF), Phan Huong Giang (UNDP)
Revival of the "Treasure of the East Sea": Ecosystem Recovery and Resource Management Efforts
October 23, 2025
Figure 1. Bach Long Vy Island (left); The nine-hole abalone (Haliotis diversicolor), a species frequently observed during scuba surveys and presented in the local trade at Bach Long Vy prior to 2013 (right)
Photos: Research Institute for Marine Fisheries (RIMF)
The Price of Plenty: Marine Treasure in Decline
Nestled far out in the vast Gulf of Tonkin lies Bach Long Vy Island, a small but strategically important outpost of Hai Phong City. Beneath its waters once thrived a precious treasure: the nine-holed abalone (scientific name Haliotis diversicolor Reeve), also known as “Bào ngư cửu khổng”, “ốc cửu khổng”, “ốc chín lỗ”, or " hoàng kim mềm". This mollusk has high economic and nutritional value, considered one of the top four most important abalone species commercially harvested in Viet Nam.
Biological Characteristics
Known as the nine-hole abalone, this mollusk is easily recognized by its sturdy sell made of calcium carbonate. While the exterior is often rough, dark green, or brown, it conceals a striking, brightly polished inner layer of mother-of-pearl. The shell's most distinctive feature is a series of respiratory holes along the edge, with typically nine of them connecting the inside to the ocean. Mature shells usually measure 6–9 cm long.
These abalone are creatures of movement and high salinity, thriving in rocky island areas with strong currents and water salinity of 21 – 32‰. They inhabit the subtidal zone, clinging to rock reefs at depths of 1 – 15 meters. Interestingly, small abalone stay closer to the shore, moving to deeper underwater reefs as they grow.
As they are plant-eaters, feeding mainly on seaweed and organic matter. As they mature, their diet changes slightly. Reproduction is sexual, with egg-laying typically occurring during the hot season, often in the late afternoon or early morning.
Since 2013, scuba surveys in the Bach Long Vy Marine Protected Area (MPA) have found it extremely rare to encounter natural abalone. A once-common sight has now become a haunting memory, raising serious concerns about the health and future of this valuable marine species. The Nine-holed abalone is on the list of 22 priority protected species of the Bach Long Vy MPA. Due to the sharp decline in its natural population, it is now listed in the Viet Nam Red Book 2024, as Critically Endangered (CR) (see Figure 1).
The Scars We Leave: Measuring the Loss of Marine Treasure
A crisis is unfolding for the nine-hole abalone in Bach Long Vi. The rapid and serious decline of this natural treasure is putting the entire "Bach Long Vy Abalone" brand at risk. As shown in research and monitoring, the catch volume has dropped dramatically, revealing in the collapse of the local abalone pollution (see Figure 2).
Research by Hai Phong’s Department of Science and Technology (2012-2013) confirmed the devastating reality: the abalone population around Bach Long Vy was in sharp decline. The study reported mass die-off of even small abalone (1–2 cm) with no signs of natural recovery.
A national project led by Research Institute for Marine Fisheries (RIMF) (2012–2015) aimed to reverse the decline by establishing a demonstration model for the production and supply of abalone seeds on the island. About 60,000 abalone were reared and 6,200 were released into the sea. However, these efforts were not enough to restore the natural population.
In 2017, facing ongoing degradation, the Bach Long Vy Marine Protected Area Management Board commissioned a study to access the situation and suggest restoration solutions. The survey revealed an extremely low average density of only 1.25 individuals per 500 square meters, around 13 times lower than in 2014. The total remaining stock was estimated at just 0.05 tons around the island.
Figure 3. A demonstration model for the production and supply of abalone seeds (above); The nine-hole abalone in scubar surveys on Bach Long Vy (below)
Photos: RIMF
The crisis is driven by excessive and uncontrolled exploitation, which has led to two critical population issues: the absence of small abalone (under 2.5 cm) and a shortage of mature, reproductive adults (over 5 cm).
This collapse is the result of a "double risk" driven by both human and environmental factors. Decades of rising market demand, combined with a lack of harvest control, have pushed the natural stock to the brink of extinction.
- Habitat Destruction and Pollution: Infrastructure development and freshwater reservoirs lead to coastal pollution from organic, plastic and solid waste, along with oil leakage, critically degrading the abalone's vital habitat.
- Destructive Fishing: The use of explosives, cyanide, and electric shock devices kill abalone, destroys reefs, and prevents regeneration from surviving.
- Broken Food Chain: Over-harvesting of Sargassum seaweed, the abalone's primary food source, leaves no chance for the population to recover.
- Dependence on Wild Seed Sources: Relying entirely on wild-caught abalone seeds prevents the growth of sustainable aquaculture, keeping all the pressure squarely on the natural abalone.
Bringing Back the Nine-Hole Abalone: A New Strategy for Bach Long Vy
Despite past short efforts, the Nine-Hole Abalone population at Bach Long Vy has not recovered, underscoring the need for a more comprehensive and targeted conservation approach.It's time to act with a new strategy focusing on three directions:
1. Heal the Habitat and Boost the Population
The first step is to improve the environment. A large-scale restocking programme should be launched, producing abalone seeds and releasing over 500,000 individuals back into their natural habitat. To guarantee success, this entire process must be followed by a three-year monitoring program to rigorously track their survival rates.
Second, restoring the Sargassum seaweed beds, the abalone's main food and shelters, is essential. Luckily, since 2023, these seaweed beds have begun to recover gradually. Last but not least, coral restoration should also be prioritized, as coral reefs provide critical protection and food sources for the abalone and many other marine species.
2.Lock down Protection and Enforcement
To give the abalone a real chance to recover, destructive fishing must stop completely. The Bach Long Vy MPA Management Board should strictly enforce bans explosives, electric fishing and toxic chemicals. Critically, a temporary ban on all abalone trade and harvesting is necessary during the recovery period. Waste dumping near sensitive areas, such as reefs and wharfs, must be stopped to prevent further damage.
3.Engage the Local Community
The survival of the nine-hole abalone depends on the involvement of local communities. Long-term policies must offer preferential loans and support programs to help residents transition to alternative livelihoods. A community-based conservation model that directly links local income with marine protection will create long-term benefits for both people and nature.
To date, RIMF is implementing a UNDP project, funded by Norway, focused on developing measures for a coral transplantation model restoration in the Bach Long Vy MPA. Restoring coral reefs not only stabilizes the marine environment and creates safe habitats and food sources but also provides vital nurseries for marine life, especially young abalone that depend on these reefs for shelter and nourishment before clinging to rock reefs. The revival of the nine-hole abalone is therefore not just about saving a single species, but about restoring balance to an entire ecosystem. With collective action from local communities, authorities, and scientists, Bach Long Vy can once again become a thriving home for this “treasure of the East Sea.”
The journey to recovery continues, and hopefully, in the near future, the shining shells of the nine-hole abalone will sparkle beneath the blue water of Bach Long Vy.
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