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Interesting Facts about Mekong Giant Catfish

[Mekong Catfish Phylum: Chordata] [Class: Actinopterygii] [Order: Siluriformes] [Family: Pangasiidae]

In June 2005, an enormous Pangasianodon gigas was collected in the Mekong River (Thailand). At 2.7 metres long and 293 kg, it was the largest species of fish to spend its whole life in fresh/brackish water.

This guide contains information and fun facts about Mekong giant catfish, including where they live, what they eat, and how they reproduce.

Mekong Catfish Current Range and Habitats

Excluding Antarctica, you can find members of the catfish species living in every continent.

Pangasianodon gigas is endemic to the Mekong River and its tributaries in Southeast Asia.

The Mekong River flows through 6 different countries, China, Myanmar, Laos, Thailand, Cambodia, and Vietnam (where it empties into the South China Sea).

However, overfishing, and dam construction have severely reduced the current range and distribution of the Mekong giant catfish.

Nowadays, they only exist in parts of northern Cambodia, southern Laos, and Thailand (albeit less common). Being a typical waterborne and riverine species, the Mekong giant catfish never enters brackish or marine waters - living exclusively in freshwater environments.

The Mekong (known as Mae Nam Khong or แม่น้ำโขง in Thai language) is a murky river that contains plenty of deep, slow-flowing stretches with large pools near rapids and rocky substrates.

Interesting Fact: Research suggests spawning is more common in northern stretches, such as northern Thailand and the Lao border. But, some conservation programs are helping to increase populations through fish sanctuaries and hatcheries where some are bred for the aquarium trade.

Characteristics of Mekong Giant Catfish

The distinctive appearance is best described as broad, with a huge torpedo-like body shape. However, the Mekong catfish lacks the "whisker" appendages (elongated barbels) seen in most other Siluriformes.

Having a flat and wide head, with a broad mouth is indicative of many freshwater bottom-feeders. Plus, their eyes are located on the underside of the head and the skin is smooth and scaleless.

Here's the thing:

As juveniles, the colour of Mekong giant catfishes tends to be subtle shades of gray or silver, with some degree of subdued or dull mottling.

But, as they grow the adults become more uniform in colouration. The gray becomes a lighter shade with white on the underbelly and a hint of silver on the back.

Mekong Giant Catfish Size and Weight

The Guinness Book of Records acknowledged a Mekong giant catfish caught in Chiang Khong, Chiang Rai province in northern Thailand.

At the time, this Mekong megafish was recognised as being the world's largest freshwater fish. However, a bigger and heavier female giant freshwater stingray (Urogymnus polylepis) outsized it after it was caught in Cambodia in 2022.

Mekong Giant Catfish Facts (Pangasianodon gigas)Records suggest the maximum size of Mekong catfish can be up to three (3) metres long (10 feet) as fully grown adults.

There are unconfirmed reports of certain specimens weighing 600 kilograms (1,300 pounds). But an average weight of 250 kilograms seems to be more accurate.

Fun Fact: The Mekong giant catfish is an enormous fish. Yet, the "gentle giant of the Mekong" is renowned for being docile and non-aggressive towards humans.

What Do Mekong Catfish Eat?

As it grows, the size of the Mekong giant catfish (Pangasianodon gigas) sees some dramatic changes. The same can also be said about its diet.

The omnivorous juveniles tend to consume small invertebrates, zooplankton, and a variety of plant material. This combination is the main reason why they grow so quickly during the early stages.

Then...

After reaching adulthood, they are almost entirely herbivorous (feeding on plants) and detritivorous (feeding on dead and decaying organic matter).

In other words, the main source of nutrition will come from algae and periphyton (such as cyanobacteria, bacteria, and different types of fungi).

Interesting Fact: One of the lesser-known facts about catfish is that they have multiple taste buds all over their body - an ideal attribute for scavengers that hunt in cloudy and turbid environments.

How Do Mekong Giant Catfish Reproduce?

Although catfish reproductive strategies vary according to the species, many display morphological characteristics (sexual dimorphism) and follow some general patterns.

Seasonal floods, rising water temperatures, and extended hours of daylight, are the usual triggers for the start of the spawning season.

Even though many catfish species build nests, they also have their preferred locations. For instance, some of the nest builders (usually the males) will choose holes in riverbanks or within dense vegetation, and others will build their nests underneath sunken logs.

In more detail...

The spawning season for Mekong giant catfish (Pangasianodon gigas) occurs once per year, most often in May or June. They time it with the rising water levels that arrive during the onset of the Mekong's rainy season.

Adults migrate hundreds of kilometres upstream from their feeding grounds to the upper Mekong to spawn. But, unlike sturgeon or salmon, this migratory process is undertaken entirely in freshwater.

Egg Laying and Parental Care

Compared with many of the typical marine vertebrate examples, it's fair to say that catfish are good parents and they take good care of their eggs.

Once the female has finished laying her sticky eggs inside the nest, often several hundred per clutch, the male goes ahead and fertilises them "externally".

In general, it's the male's role to guard the nest against predatory hunters. He also uses his fins to fan the eggs and oxygenate them by circulating the water.

Hatching into Baby Catfish

Like many of the jawfish species, some catfish are also mouthbrooders that carry eggs or "live" young inside the mouth for extra protection.

Within a few days the eggs start to hatch, and the young fry (baby catfish) rarely move far away from the safety of the nest. They will start to swim freely once they have completely absorbed the yolk sac.

Interesting Facts: The males of some catfish species are internal fertilisers that use their intromittent organ (a modified anal fin) during copulation. Others spawn inside caves, and some South American catfish (Corydoras) store their eggs inside a pouch (modified pelvic fins) and attach them to plants after they have been fertilised.

Mekong Catfish Predators and Threats

Few ray-finned species can match the toughness and diversity of the catfish families. Still, Mekong giant catfish face limited natural predators, but a few significant human-induced threats.

In their natural habitats, the main predators of Mekong catfish are small fish, aquatic invertebrates, and birds that prey on the eggs and larvae.

However, some of the reasons behind a serious decline in populations include:

Important: An assessment released by the IUCN Red List of Threatened Species shows the conservation status of most catfishes worldwide is of "Least Concern" (LC). However, data recorded in 2011 shows that the Mekong Giant Catfish (Pangasianodon gigas) is "Critically Endangered" (CR) with a "Decreasing" population trend.

Related Information and Help Guides

Note: The short video [1:57 minutes] presented by "Deep Marine Scenes" contains even more catfish facts with some fascinating footage of the striped eel catfish (Plotosus lineatus).

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