In-depth research on “Lich Cu” eel group: From new species discovery to conservation recommendations

Along the coastal and estuarine zones from Vung Tau to Ben Tre, where diverse ecosystems such as mangroves, mudflats, and major estuaries converge, there exists a special group of eels locally known as “lich cu.” This popular term refers to very long-bodied eels, mostly from the family Ophichthidae, that burrow into the seabed and have high commercial value, with some species selling for 500,000–700,000 VND/kg. Despite their ecological and economic importance, scientific information on the species composition, biological characteristics, and resource status of this group remains limited.

To conduct an in-depth study, Dr. Vo Van Quang and his team from the Institute of Oceanography, Vietnam Academy of Science and Technology, implemented the project “Biological Characteristics and Resource Status of ‘Lich Cu’ Eels (Ophichthidae) in the Coastal and Estuarine Areas from Vung Tau to Ben Tre and Solutions for Sustainable Resource Development” (code: VAST06.05/23–24).

Dr. Vo Van Quang at a scientific conference

According to Dr. Vo Van Quang, the research team collected samples from two eel groups, focusing mainly on “lich cu.” To ensure representativeness and diversity, multiple field methods were combined. Samples were taken from fishing vessels using common gear at five main sites, including ports and landing areas. Additionally, nine offshore stations were surveyed using trawl nets to expand the sampling area. Collecting Pisodonophis (snake eels) proved difficult due to their low occurrence, large size, and high market value—fishermen often kept them for sale, resulting in limited samples.

Map showing sampling locations of “lich cu” eels

The study identified five representative “lich cu” species, including two new species described for science: the Cuulong fat eel (Ophichthus cuulongensis Vo, Hibino & Ho, 2025) and the black-bodied long eel (O. nguyenorum Vo, Hibino & Ho, 2025). The others are the high-finned snake eel (O. macrochir), the double-toothed snake eel (O. rutidoderma), and the grain-toothed eel (Pisodonophis cf. boro).

The team also published two new species of deep-sea benthic eels belonging to the families Dysomma and Dysommina (Synaphobranchidae) in the Journal of Fish Biology. Dysomma intermedium is distinguished by a body length comprising 50% of its head length, unique fin and tooth structures, 70–76 lateral line pores, and 118–124 vertebrae. Dysommina brevis is notable for its exceptionally short body, large eyes, and reduced number of teeth compared with other species in the same genus.

Two additional new Ophichthus species were published in ZooKeys, a peer-reviewed taxonomy journal. Both species possess elongated bodies, distinctive colouration, and unique cranial bone structures. The team also redescribed two known species (O. macrochir and O. rutidoderma) to standardise taxonomic data and prevent future misidentifications.

Notably, this research marks the first record in Vietnam of Meadia roseni Mok, Lee & Chang, 1991 (Synaphobranchidae), a rare deep-sea eel species previously known only from Taiwan’s waters. This finding, published in Acta Ichthyologica et Piscatoria, adds valuable data to Vietnam’s deep-sea benthic fauna, a region that remains largely underexplored.

Among the species discovered, Ophichthus cuulongensis (fat eel) stands out for both its ecological and economic value. The species can reach up to 104.6 cm in length, reaching sexual maturity at 68.5 cm. Spawning occurs year-round, with two peak periods in February–March and June–July. A single female can produce an average of over 31,000 eggs, or about 308 eggs per gram of body weight. Its main diet includes crustaceans such as sand crabs and small shrimps.

Commercially, “lich cu” eels are mainly caught using traditional gear such as pair trawls, single trawls, bottom nets, lift nets, traps, and manual digging. The trawl fishery accounts for about 2.7% of the total regional catch. Annually, the area yields 150–180 tonnes of “lich cu” eels, with an estimated stock biomass of 300–350 tonnes.

To protect and sustainably manage “lich cu” resources, the research team proposed a series of specific management measures. For Ophichthus cuulongensis, the economically valuable species, they recommended harvesting only individuals over 68.5 cm in length. Fishing gear should have mesh sizes larger than 20 mm to avoid catching juveniles. In particular, trawling should be restricted or banned in shallow waters under 10 metres, where the species typically lives and breeds. Fishing should also be suspended in estuarine areas during peak spawning months (March and September) to allow stock recovery. Strengthening coastal patrols and regulating nearshore fishing activities were also emphasised to reduce overfishing pressure.

The study’s findings significantly enhance understanding of Vietnam’s marine biodiversity and provide a crucial scientific basis for ecosystem protection and sustainable exploitation of the “lich cu” eel resources in the future.

Translated by Tuyet Nhung
Link to Vietnamese version