World Biggest Freshwater Fish is the Giant Mekong catfish

                            

What we see in the fish tank is not real....This the ever biggest freshwater fish found on earth. The dimensions of these catfish are very impressive, with the largest supposedly growing up to 10ft/3m and weighing up to 660lbs/300kg. This creature is 5 times bigger than the 'world record' catfish found in North America.

The biggest one ever captured and measured was caught in Thailand in May of 2005.

The fish in the photo below was captured by some fisherman where the species is considered endangered, but can still be caught with special permits. The fish was turned in to the Department of Fisheries where the eggs and sperm are collected from these rare giants and harvested for a captive breeding program to keep the species alive.

Scientists have recently discovered someting amazing about the Giant Mekong catfish; they live out part of their lives at sea. Most people have the impression of catfish as slow, lumbering bottom-feeders, but it turns out that the migration routes of these catfish rival those of the better known salmon. Scientists have recorded Pangasius gigas traveling as much as 600 miles (1000 km) inland from the south China sea up the Mekong River to spawn.

The waters of the Mekong River are very murky and make it difficult to track the movements of the fish. In order to determine where the Mekong catfish have been, scientists examined chemical markers called isotopes in bone and muscle tissue of catfish from the Khone Falls region of the Mekong. The team found evidence that the freshwater-dwelling fish had migrated recently from a marine habitat. Although this method of fish tracking is a highly regarded method, it appears that this is the first time it has been used to track the migration routes of river catfish species from a marine environment.

As big as the Giant Mekong catfish can get, there are rumored to be other species of freshwater fish whose dimensions rival those of the Mekong catfish. Among them are the Arapaima and huge freshwater stingrays, both found living in the Amazon River. The giant Chinese paddlefish is also a serious contender for world's biggest freshwater fish, but very little is known about this species that seems to be rapidly disappearing.