The strange appearance of the fish species recorded for the first time in Vietnam

(Dan Tri) - This discovery not only adds to Vietnam's marine biodiversity treasure but also has important significance in the conservation and sustainable exploitation of aquatic resources.

Many new discoveries about fish

Along the coastal and estuary areas from Vung Tau to Ben Tre, there is a convergence of diverse ecosystems such as mangrove forests, alluvial plains, and large estuaries, where a special group of fish exists that local fishermen call "lich cu".

This is a folk name for very long fish species, usually belonging to the family Ophichthidae, living buried in the bottom and having high commercial value, some species have a selling price of up to 500-700 thousand VND/kg.

Diagram of survey location for collecting samples of "old calendar" fish (Photo: VAST).

Although playing an important role in the coastal ecosystem and livelihoods, scientific information on species composition, biological characteristics and resource status of this fish group is still very limited.

To conduct in-depth research on this group of fish, Dr. Vo Van Quang and a group of scientists from the Institute of Oceanography , Vietnam Academy of Science and Technology conducted the following topic:

“Biological characteristics and current status of resources of “Lich Cu” fish belonging to the family Ophichthidae in coastal and estuary areas from Vung Tau to Ben Tre and proposed solutions for sustainable resource development”.

Dr. Vo Van Quang at a scientific conference (Photo: VAST).

According to Dr. Quang, the research team collected samples from two different fish groups, of which "old calendar" was the main subject.

To ensure representativeness and diversity of the sample, multiple field methods were combined. Samples were collected from fishing vessels using common fishing gear such as trawlers, nets, and traps at five main locations, including fishing ports and landing sites.

In addition, the team also conducted surveys at 9 offshore stations using trawl nets to expand the sampling range. As for eels, collection was difficult because this species has a low frequency of occurrence, large size and high commercial value, so it is often kept by fishermen for consumption, making the number of collected samples quite limited.

During the survey and research, the group identified 5 typical fish species belonging to the "old calendar" group.

Notably, two new species to science were described, including the Ophichthus cuulongensis (Vo , Hibino & Ho, 2025) and the Ophichthus nguyenorum ( Vo , Hibino & Ho, 2025). The remaining species are the Highfin Snake Eel ( O. macrochir ), the O. rutidoderma and the Pisodonophis cf. boro .

The team also announced two new species of fish to science belonging to the deep-dwelling fish families. Of these, two species belong to the genera Dysomma and Dysommina (family Synaphobranchidae), published in the Journal of Fish Biology .

In addition, two other new species of the genus Ophichthus have also been published in the international journal ZooKeys , a specialized journal of taxonomy.

Both have elongated bodies, distinctive coloration, and distinct skull structures. The team also described two known species ( O. macrochir and O. rutidoderma ) to standardize taxonomic data and avoid confusion in future studies.

Fish species recorded for the first time in Vietnam

In particular, this is the first time in Vietnam that the appearance of the Eel species Meadia roseni Mok, Lee et Chang, 1991 (family Synaphobranchidae), a rare deep-water Eel species, previously only known in some sea areas in Taiwan (China) was recorded.

This discovery, published in the journal Acta Ichthyologica et Piscatoria , contributes to the deep-sea benthic database for Vietnam, an area that has been little surveyed.

Among the discovered species, the Fatty Elk stands out in both ecological and economic value. This species can grow to a maximum length of 104.6cm, and reaches sexual maturity at 68.5cm or more.

Fish spawn all year round, but are concentrated in two periods: February-March and June-July. A female can lay an average of more than 31,000 eggs, equivalent to about 308 eggs per gram of weight.

The main food is crustaceans such as wild gourami and small shrimp. In terms of exploitation, "lich cu" fish is currently caught mainly by traditional fishing gear such as double rakes, single rakes, bottom nets, nets, traps and burrowing methods.

Need reasonable exploitation solution

In order to protect and reasonably exploit the resources of the “old caltrop” fish, the research team has proposed a series of specific management solutions. In particular, the “old caltrop”, a species with high economic value, is recommended to only exploit when it reaches a length of over 68.5cm.

Fishing gear should have mesh sizes larger than 20mm to avoid catching juvenile fish. In particular, the group recommends restricting or banning trawling in shallow waters less than 10m deep, where this species often lives and breeds.

At the same time, it is necessary to temporarily stop fishing at the river mouth during peak spawning months (March and September), giving fish a chance to regenerate their populations.

In addition, increased patrolling and control of coastal fishing vessel activities is also emphasized to reduce overfishing pressure.

The group's research results have contributed to expanding understanding of Vietnam's marine biodiversity and providing an important scientific basis for protecting ecosystems and sustainably developing "old-fashioned" fish resources in the future.

Source: https://dantri.com.vn/khoa-hoc/ve-ngoai-ky-di-cua-loai-ca-lan-dau-tien-ghi-nhan-o-viet-nam-20250820080415288.htm