During 2023–2024, a research team from the Institute of Biology (Vietnam Academy of Science and Technology – VAST), in collaboration with the Graduate University of Science and Technology (VAST) and the Center for Technology and Nature Conservation, carried out an extensive survey to document the fish species composition in freshwater bodies, as well as tung and ang (karst sinkhole lakes and semi-enclosed lagoons) on the islands of Bai Tu Long Bay and Ha Long Bay. This represents one of the few dedicated studies on these semi-isolated karst water systems—often considered “forgotten biological refugia” within the World Heritage landscape.
Led by researchers Nguyen Dinh Tao, Le Hung Anh, and Hoang Anh Tuan, the study generated significant findings and contributed valuable baseline data for the conservation of island and cave ecosystems in Quang Ninh province.
A comprehensive biodiversity profile: 48 species, 38 genera, 31 families
Across numerous field trips to the islands of Quan Lan, Minh Chau, Ngoc Vung, Ban Sen and several major tung–ang systems such as Ang Cai Lim, Ang Cai De, and Tung Soi Nhu, the researchers collected fish specimens through multiple sampling methods, including hook-and-line fishing, traps, gillnets, cast nets, electric fishing, and hand nets.
The survey documented 48 species, belonging to 38 genera, 31 families, and 18 orders. Perciformes was the dominant order, with 11 species (22.9%), underscoring the ecological prominence of coastal–brackish fish in the region’s semi-enclosed systems. Gobiiformes followed with 9 species (18.7%), and Acanthuriformes with 4 species (8.3%). Other orders—such as Cypriniformes, Mugiliformes, Clupeiformes, and Siluriformes—were represented by only one to three species each.
Importantly, the species composition clearly reflects the transitional ecological nature of tung–ang, where freshwater, brackish, and marine conditions interact within confined, isolated karst basins.
Comparing the two bays: Bai Tu Long shows higher diversity
One of the most notable outcomes of the study is the distinct difference in species richness between the two regions:
- Bai Tu Long Bay: 40 species
- Ha Long Bay: 32 species
Freshwater streams and lakes on the islands: only 8 species.
These numbers indicate that the tung–ang systems in Bai Tu Long Bay experience fewer disturbances and provide more heterogeneous habitats, particularly in substrate composition, water movement, and salinity variation.
In contrast, the freshwater bodies on the islands hosted only a few highly adaptable species such as Macropodus opercularis, Misgurnus anguillicaudatus, Channa striata, Gambusia affinis, and Oreochromis niloticus. These habitats also showed clear signs of pressure from invasive species, especially Gambusia affinis and Oreochromis niloticus, which pose severe competition to native fish communities.
Fifteen economically valuable species – key resources for coastal livelihoods
Among the 48 recorded species, the research team identified 15 economically important species (31.3%), which play an essential role in the livelihoods of island communities.
Representative species include: Siganus guttatus (Golden rabbitfish), Sillago sihama (Silver sillago), Acanthopagrus berda (Black seabream), Moolgarda crenilabis (Crenulated mullet), Monacanthus chinensis (Fan-bellied leatherjacket)
These species maintain stable harvest levels, enjoy strong consumer demand, and are vital to local fisheries. However, the authors emphasize the urgent need for science-based management and long-term monitoring to secure sustainable exploitation.
An endangered species recorded – a warning for the region’s biodiversity
A critical finding of the study is the presence of Evynnis cardinalis, an Endangered (EN) species listed in both the IUCN Red List (2025) and the Vietnam Red Data Book (2024).
Once widely distributed along northern Vietnam’s coastal waters, the species has sharply declined due to overfishing, habitat alteration, pollution, and climate change. Its occurrence in semi-enclosed tung–ang highlights the role of these systems as ecological refuges that offer shelter from large-scale fishing pressures.
Emerging threats: invasive species and climate change
Field data show that many tung–ang systems are under increasing stress:
Invasive species (Oreochromis niloticus, Gambusia affinis)
These species reproduce rapidly, compete aggressively for food, and disrupt native fish assemblages. In several island freshwater bodies, Oreochromis niloticus appears to be becoming dominant.
Pollution and climate change: Many sites showed signs of heavier sediment accumulation, irregular salinity and temperature fluctuations, and a decline in benthic algae and macrophytes—key food sources for several economic species. Such changes make local fish populations more vulnerable to ecological disturbances.
Ecological significance: Contributing 10.4% of the region’s total fish fauna
According to Kimura et al. (2018), Ha Long Bay hosts approximately 460 fish species. The new study demonstrates that tung–ang and island freshwater bodies alone account for about 10.4% of the total regional fish fauna. This underscores the unique ecological role of these karst systems, which serve as transitional habitats between freshwater, brackish, and marine environments and act as important corridors for species within the Indo–West Pacific biogeographic region.
The study also identified several specimens not yet resolved to species level within the genera Ambassis, Gerres, Stolephorus, Eubleekeria, Leiognathus, Acentrogobius, and Rhinogobius, suggesting potential avenues for future research into morphological variation or unidentified taxa.
Valuable baseline data for conservation and sustainable management
The survey conducted by the Institute of Biology and its partner institutions has produced the most comprehensive baseline dataset to date on the fish assemblages of tung–ang and island freshwater systems in Bai Tu Long–Ha Long. These findings will: support more effective conservation planning; inform ecotourism development aligned with ecosystem protection; provide scientific evidence for environmental impact assessments; create a foundation for advanced research in the future.
Amid the challenges of climate change and pressures from tourism and resource exploitation, reliable scientific data such as these are critical to safeguarding the unique biodiversity of Vietnam’s world-renowned natural heritage region.
In the context of accelerating climate change, sea-level rise, and increasingly severe coastal erosion in the Mekong Delta, field-based scientific evidence on the coastal protection functions of mangrove forests (MF) has become critically important for shoreline planning and management. Recently, a research team comprising Ly Trung Nguyen, Danh Tinh, and Le Thanh Khang from the College of the Environment and Natural Resources, Can Tho University, completed a large-scale field study in coastal mangrove forests located in the former Soc Trang province, now administratively part of Can Tho city.
In the context of rapidly increasing municipal solid waste (MSW) generation in urban areas, digital transformation is opening significant opportunities to improve the efficiency of waste collection, transportation, treatment, and recycling. The study conducted by Phan Thi Hai Luyen and Pham Quang Dung (Vietnam National University of Agriculture) provides a comprehensive overview of digital technologies—including the Internet of Things (IoT), Artificial Intelligence (AI), Big Data, Geographic Information Systems (GIS), and smart management models—together with a SWOT analysis assessing the feasibility of applying such technologies in Vietnam. Findings indicate that digital transformation can deliver substantial improvements, although challenges remain in terms of infrastructure, investment costs, and public awareness.
In recent years, agriculture has continued to play an important role in Quang Ninh’s local economic structure and remains a key source of livelihoods for tens of thousands of farming households. Beyond its economic contribution, the sector underpins rural employment and social stability across many districts. However, the development of key agricultural product value chains in the province still faces persistent challenges, including fragmented small-scale production, aging fruit orchards, unstable consumption markets, and increasing risks associated with climate change.
In the U Minh Thuong area (formerly Kien Giang province, now part of An Giang), the shrimp–rice system has long been regarded as a key production model. Yet in recent years, the system has been under pressure due to salinization, soil degradation, and continuous shrimp farming, all of which have contributed to declining yields and deteriorating water quality. A research team from Can Tho University conducted a field trial using two native aquatic plant species — Nan tuong (Scirpus littoralis) and Co nuoc man (Paspalum vaginatum) — in shrimp ponds. Their findings show that these plants can improve water conditions and increase black tiger shrimp productivity by 14–21%, offering a promising biological management approach for shrimp–rice systems in the Mekong Delta.
A research team from the Institute of Materials Science, Vietnam Academy of Science and Technology (VAST)—including Le Thi Hai Ninh, Pham Thi Hai Thinh, Nguyen Duc Nui, and Duong Van Nam—has carried out a study on phosphorus recovery from natural rubber processing wastewater using the struvite precipitation method.
