Predatory fish of the Amazon

Mekong giant catfishBy definition, a Megafish is greater than 6ft in length – larger than the average human. They’re mostly found in freshwater systems and are benthic i.e. they live on the bottom of the riverbed. Some are gentle giants, feeding on algae and plankton, others are voracious feeders who grab animals from the banks and pull them into the water.

These fish have what’s known as “indeterminate growth”, growing larger as long as they live without disease or predation. So the larger fishes also tend to be the oldest ones.

The largest freshwater fish ever captured was the Mekong Catfish from Thailand. Typically reaching around 200kg, and 7/8 feet, this fish hadn’t stopped growing throughout its life. A research expedition on the Mekong river captured a 300kg, 10 foot beast – the “size of a grizzling bear”. as part of a breeding programme, hoping to release it, but the fish died in captivity and was sold as food to local villagers.

The Mekong Catfish is only one of many (the titanic Freshwater Stingray also lives in the Mekong river). The Arapaima of Brazil is an Amazon fish which mostly eats small fish and crustaceans – but occasionally grabs animals that stray too close to its habitat. The Arapaima is an air-breather: a complex set of tubes feed oxygen into its blood, because the lakes it live in contain next to no dissolved oxygen.

Unsurprisingly, because the fish are so large, they are important as food. In the case of the Mekong catfish: as populations boomed in Thailand in the 1960s the fish numbers dwindled until none were being caught along the river. at an uncertain future. Other fish, such as the Chinese sturgeon and the “Mongolian Terror Trout” (dubbed by the National Geographic) have also seen declining populations.

The question of why these populations are declining is important. Like the Panda or Polar Bear, they are recognisable and enigmatic flags of the welfare of their habitats. If the Mekong river is being polluted by Bangkok, the catfish tells that story.

The Hucho Taimen - also known as the Mongolian Terror TroutZeb Hogan is the man behind the Megafish project, taking a global census of the Megafish population around the world. The project, which spans almost every continent, is the subject of the National Geographic documentary Quest For The Megafish. The project is ongoing, but has yet to publish any findings.

Little is said about marine giant fish, probably because of their large habitat and often wide or unpredictable migrations. While sharks typically are the largest marine fish, the Sturgeon family can achieve incredible sizes, including one which weighed half a ton.

The largest-growing fish alive today is the Whale Shark (largest capture is 12.65m), which is herbivorous. The largest fish to ever live was the Megalodon, said to grow up to 30m.


Jungle Jaws
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90% of predatory species in the ocean

2005-10-31 20:37:58 by have_been_destroyed

I love seafood in general but will no longer consume it on ethical grounds.
Please folks, get your omega-3 fatty acid from walnuts and give the oceans a break.Fishing methods are extremely inhumane, fish farms are incredible polluters and disease hot-spots that decimate wild populations, factory trawling and long-line nets turn the ocean bottom into ecological deserts by destroying everything in their path and killing thousands of "non-target" critters (think of plowing a 5 to 20-mile wide bulldozer through the Amazon).
And if you think I'm just another alarmist nut, check this out: (from


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