Wallago

Handle with care

Wallago attu

Also known as: Freshwater Shark, Boal, Mural, Lanchi, Mali, Barwari

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Description

Wallago attu, commonly known as the Wallago or Freshwater Shark, is a large, predatory catfish belonging to the family Siluridae. It is characterized by its elongated, compressed body, large mouth, and prominent barbels. This species is a significant component of freshwater ecosystems across South and Southeast Asia, playing a crucial role as an apex predator. It is highly valued as a food fish and is also sought after by recreational anglers.

Physical Characteristics

Body shape: eel-like
Coloration: Dorsal surface typically dark grey to brownish-green, fading to silvery-white on the ventral side. May have irregular dark blotches or spots, especially in younger individuals. Fins are generally dusky.
Scale type: none
Mouth position: superior
Distinctive features: Extremely elongated and compressed body, particularly towards the caudal fin., Very large, wide mouth extending beyond the eye., Two pairs of barbels: one pair of long maxillary barbels reaching beyond the pectoral fin, and one pair of short mandibular barbels., Small, widely spaced eyes located dorsally., Absence of an adipose fin., Anal fin is exceptionally long, extending from behind the anus almost to the caudal fin.
Dorsal fin: Very small, with 5 soft rays, located far forward, anterior to the pelvic fins.
Tail fin: Forked, with pointed lobes.
Pectoral fin: Relatively large and pointed, with a strong, serrated spine.
Distinctive fins: Anal fin is extremely long, with 77-97 soft rays, confluent with the caudal peduncle but not joined to the caudal fin.

Identification Tips

Body Shape

Look for the distinctly elongated, compressed, and eel-like body, especially the posterior half.

Mouth and Barbels

Observe the very large, wide, superior mouth and the two pairs of barbels, particularly the long maxillary barbels.

Dorsal Fin

Note the extremely small dorsal fin located far forward on the body.

Anal Fin

Identify the exceptionally long anal fin that runs almost the entire length of the posterior body.

Absence of Adipose Fin

Confirm the lack of an adipose fin, which is common in many other catfish species.

Habitat

Water type: freshwater
Depth: Typically found in shallow to moderately deep waters, but can inhabit deeper pools.
Environment: Inhabits large rivers, canals, lakes, reservoirs, and floodplains. Prefers turbid waters with muddy or silty bottoms and areas with submerged vegetation or debris for cover. Tolerant of a wide range of water conditions.
Geographic range: Widely distributed across South and Southeast Asia, including Pakistan, India, Bangladesh, Sri Lanka, Nepal, Myanmar, Thailand, Laos, Cambodia, Vietnam, Malaysia, and Indonesia (Sumatra, Java, Borneo).

Aquarium Information

Care level: expert
Temperament: aggressive
Diet: carnivore
Minimum tank size: 1000 gallons (for adult specimens)
Temperature: 22-28°C (72-82°F)
pH level: 6.0-7.5
Hardness: 5-15 dGH
Compatibility: Not suitable for community tanks. Can be kept alone or with other very large, robust, and equally aggressive fish that cannot be swallowed. Requires careful consideration for tank mates.
Special requirements: Requires an extremely large aquarium with powerful filtration due to its size and predatory nature. Needs ample swimming space and hiding spots. Substrate should be soft to prevent injury to its barbels. Excellent lid security is essential as they are known jumpers.

Wild Information

Conservation status: least concern
Seasonality: Spawns primarily during the monsoon season (June-September) in most parts of its range, when water levels rise and flood plains become accessible. Fishing activity often increases during non-spawning periods.
Market price: Varies significantly by region and size, often fetching high prices in local markets due0 to its size and taste.
Commercial importance: high
Taste: Mild, slightly oily, and distinctive.
Texture: Firm, flaky, and white flesh with minimal bones.
Cooking methods: Curry, Fried, Grilled, Steamed, Smoked
Nutritional value: Good source of protein and omega-3 fatty acids.

Key Facts

Apex Predatorbehavior

Wallago attu is a top predator in its freshwater habitats, feeding on a wide variety of fish, crustaceans, and even small terrestrial animals that fall into the water.

Nocturnal Hunterbehavior

This species is primarily nocturnal, becoming most active during the night to hunt for prey.

Mouth Sizeinteresting

Its exceptionally large mouth allows it to swallow surprisingly large prey whole, a key adaptation for its predatory lifestyle.

Longevityinteresting

Wallago attu can live for over 10 years in optimal conditions.

Cultural Significanceinteresting

In many parts of its range, Wallago attu is not only a significant food fish but also features in local folklore and fishing traditions.

Safety Information

Handle with care

Safety level: caution
Venomous: No
Edibility: edible
Handling notes: Wallago attu possesses sharp pectoral fin spines that can inflict painful wounds if handled carelessly. Its large mouth and powerful jaws can also deliver a significant bite. Exercise caution when handling, especially large specimens. Use appropriate tools like lip grippers or thick gloves if necessary. There are no known venomous glands associated with its spines.

Similar Species

Ompok bimaculatus

Ompok species generally have a shorter, deeper body, a smaller mouth, and typically two pairs of barbels, but the maxillary barbels are usually shorter than in Wallago attu. Ompok also often has a distinct black spot behind the gill cover, which Wallago attu lacks.

Wallagonia leerii

Wallagonia leerii (formerly Wallago leerii) is another large predatory catfish, but it typically has a more robust body, a broader head, and often a more pronounced pattern of spots or blotches. Its distribution is more restricted to parts of Southeast Asia.

Scientific Classification

Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Siluriformes
Family: Siluridae
Genus: Wallago
Species: attu

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