{"id":21324,"date":"2026-08-01T08:48:37","date_gmt":"2026-08-01T03:03:37","guid":{"rendered":"https:\/\/eng.dragonmedia.com.np\/?p=21324"},"modified":"2026-08-01T08:48:37","modified_gmt":"2026-08-01T03:03:37","slug":"the-mystery-of-eels-sea-born-indian-mottled-eels-and-mud-dwelling-cuchia","status":"publish","type":"post","link":"https:\/\/eng.dragonmedia.com.np\/?p=21324","title":{"rendered":"The Mystery of Eels: Sea-Born Indian Mottled Eels and Mud-Dwelling Cuchia<\/strong>"},"content":{"rendered":"

Dragon Media News Desk<\/strong><\/p>\n

With the onset of the rainy season, long, snake-like fish begin appearing in muddy fields, canals, ponds and wetlands. In different parts of Nepal, such fish are commonly called bam, rajbam, cuchia, hilebam or chusi bam. Although they may look similar, these local names do not refer to a single species.<\/p>\n

Some are true eels, others are swamp eels, while some belong to groups of spiny freshwater fish. Therefore, the belief that all eel-like fish found in fields are born in the ocean is scientifically incorrect.<\/p>\n

Among the elongated fish recorded in Nepal, the Indian mottled eel, or Anguilla bengalensis, has a life cycle linked to both the ocean and rivers. By contrast, species such as the cuchia, Monopterus cuchia, and the tire-track spiny eel, Mastacembelus armatus, grow and reproduce in freshwater, wetlands and river systems.
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\nIndian Mottled Eel: A True Eel Born in the Ocean and Raised in Rivers<\/strong><\/p>\n

The scientific name of the Indian mottled eel is Anguilla bengalensis. It belongs to Anguillidae, the family of true freshwater eels.<\/p>\n

Scientists describe it as a catadromous fish. This means it spends most of its growth period in rivers, lakes, reservoirs or brackish water, but returns to the ocean to reproduce after reaching maturity.<\/p>\n

The Indian mottled eel can live in deep river sections, beneath rocks, in muddy waters, lakes, ponds and reservoirs. Its presence has been recorded in Nepal\u2019s Terai and lower river systems.<\/p>\n

Its life cycle begins with eggs laid in the open ocean. The newly hatched larva does not resemble an ordinary fish fry. Its body is transparent, leaf-shaped, thin and laterally compressed. This stage is known as the leptocephalus.<\/p>\n

After travelling with ocean currents, the larva reaches waters near a river mouth and transforms into a glass eel. At this stage, it is small and almost transparent. As colour gradually develops, it becomes known as an elver.<\/p>\n

Elvers swim upstream against the river current and may reach tributaries, reservoirs, wetlands and inland waters. The stage during which the eel feeds and grows in rivers for several years is called the yellow eel phase.<\/p>\n

As it matures, the underside of its body becomes silvery, its eyes grow larger and fat accumulates to provide energy for a long migration. It is then known as a silver eel.<\/p>\n

The silver eel travels downstream and returns to the ocean to reproduce. Scientists generally believe that most true eels complete their life cycle after spawning at sea.<\/p>\n

However, the exact oceanic breeding grounds of Anguilla bengalensis found in Nepalese rivers have not yet been conclusively identified. Parts of the Indian Ocean are considered possible spawning areas, but there is still insufficient research tracking adult eels from Nepalese rivers to their actual breeding grounds.<\/p>\n

Cuchia: A Mud-Dwelling Fish That Can Breathe Air<\/strong><\/p>\n

The cuchia, commonly found in Nepal\u2019s Terai, marshes, rice fields, wetlands and slow-moving waters, has the scientific name Monopterus cuchia. Older scientific records also refer to it as Amphipnous cuchia.<\/p>\n

The cuchia is not a true eel related to the Indian mottled eel. It is a freshwater fish belonging to the swamp eel group.<\/p>\n

Its body is extremely long, cylindrical and snake-like. It lacks clearly visible pectoral fins. Its body is specially adapted to life in wetlands and allows it to survive in muddy water with very low oxygen levels.<\/p>\n

The cuchia can also absorb oxygen from the air. When water begins to dry up, it may burrow into the mud and remain inactive for a long period under unfavourable conditions.<\/p>\n

When rainfall returns and the ground becomes wet, the cuchia becomes active and emerges from its burrow. This is why people may think that the fish has suddenly appeared or originated in the field after rainfall.<\/p>\n

The cuchia, however, does not reproduce in the ocean. It lays eggs in freshwater, mud or wetland habitats and does not need to migrate to the sea to complete its life cycle.<\/p>\n

It feeds on small fish, tadpoles, earthworms, insects and other aquatic organisms. Its ability to live in mud, breathe air and survive outside water for a limited period makes it entirely different from the Indian mottled eel.<\/p>\n

Tire-Track Spiny Eel: Called an Eel but Not a True Eel<\/strong><\/p>\n

Another elongated fish found in Nepal is the tire-track spiny eel, or Mastacembelus armatus. It is also known in English as the zigzag eel, tire-track eel or marbled spiny eel.<\/p>\n

Although its body is long, it does not belong to the true Anguilla eel group. It is called a spiny eel because of the small, separate spines along its back.<\/p>\n

The tire-track spiny eel is among Nepal\u2019s native freshwater fish. It is found in the Koshi, Narayani, Karnali and Mahakali river systems.<\/p>\n

It has a somewhat elongated and pointed snout. Dark zigzag, striped or net-like patterns can be seen across its body. The separate small spines in front of the dorsal fin help distinguish it from both the Indian mottled eel and the cuchia.<\/p>\n

It lives in rivers, streams, ponds and other freshwater habitats. The ocean-bound reproductive migration of the Indian mottled eel does not apply to this species.<\/p>\n

Where Do Eel-Like Fish in Fields Come From During the Rainy Season?<\/strong><\/p>\n

During the rainy season, temporary water connections develop among rivers, streams, canals, ponds, wetlands and rice fields. Floodwater or rising water levels may allow Indian mottled eels and tire-track spiny eels to enter new aquatic areas.<\/p>\n

When the water recedes, the fish may become trapped in fields, depressions, canals or ponds. An Indian mottled eel found in such a place may have travelled there through the river system.<\/p>\n

The situation is different for the cuchia. It may already have been hiding inside a burrow in the mud, wetland or edge of a field. Once rain moistens the ground, it becomes active and emerges, creating the impression that it has suddenly appeared.<\/p>\n

Therefore, it is scientifically incorrect to assume that every elongated fish found in a field during the rainy season has migrated from the ocean.<\/p>\n

How to Distinguish the Three Fish<\/strong><\/p>\n

Indian Mottled Eel \u2014 Anguilla bengalensis<\/p>\n

It has clearly visible pectoral fins on both sides behind the head. The dorsal, tail and anal fins join to form a long, continuous fin around the rear of the body. Spots or mottled patterns may be visible. It is a true eel that migrates between the ocean and rivers.<\/p>\n

Cuchia \u2014 Monopterus cuchia<\/strong><\/p>\n

Its body is nearly uniform in thickness, cylindrical and highly snake-like. It lacks clearly visible pectoral fins. It also does not have the prominent continuous fin margin seen in the Indian mottled eel. It lives in mud, breathes air and reproduces in freshwater.<\/p>\n

Tire-Track Spiny Eel \u2014 Mastacembelus armatus<\/p>\n

It has a long, slightly pointed snout. Separate small spines occur along the back, while zigzag or net-like patterns appear on the body. It is a freshwater spiny eel-like fish and does not migrate to the ocean to reproduce.<\/p>\n

A Mystery Dating Back to Aristotle<\/strong><\/p>\n

The ancient Greek philosopher Aristotle could not find clearly visible eel eggs, young or reproductive organs. He therefore suggested that eels emerged spontaneously from mud. That idea has long since been proven wrong.<\/p>\n

Modern science has established the general life cycle of true freshwater eels: birth in the ocean, movement of larvae toward river mouths, growth in rivers for several years and a return to the ocean for reproduction.<\/p>\n

Yet not every mystery has been solved. The exact spawning grounds of many tropical eel species remain uncertain. Scientists are also still studying how adult eels navigate across thousands of kilometres and how reproduction takes place in deep ocean waters.<\/p>\n

Conservation Challenges<\/strong><\/p>\n

The Indian mottled eel requires an uninterrupted water route between rivers and the ocean to complete its life cycle. Dams, hydropower structures, irrigation barriers and artificial alteration of rivers may prevent young eels from moving upstream and mature eels from returning to the ocean.<\/p>\n

Pollution, changes in natural river flow, destruction of wetlands, pesticide use and excessive fishing can affect Indian mottled eels, cuchia and tire-track spiny eels alike.<\/p>\n

When Nepal develops hydropower projects, embankments or irrigation infrastructure, safe passage and natural water connections should be maintained not only for large commercially valuable fish but also for lesser-known species that move between rivers, wetlands and agricultural fields.<\/p>\n

Conclusion<\/strong><\/p>\n

The phrase \u201cguests of the rivers, children of the ocean\u201d is scientifically appropriate for the Indian mottled eel. It is born in the ocean, grows in rivers and returns to the sea to reproduce.<\/p>\n

However, the same story does not apply to every elongated fish found in muddy fields during the rainy season. The cuchia lives in mud and freshwater, breathes air and reproduces within local aquatic habitats. Tire-track spiny eels and other spiny eel species are also freshwater fish.<\/p>\n

The mystery, therefore, lies not only in the unusual life of eels but also in the different species concealed behind a single local name. Without accurate scientific identification, turning the extraordinary ocean migration of one species into the shared story of every elongated fish may produce an appealing narrative, but not a fully accurate one.<\/p>\n

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