They might be a the longest but there's several that top them in size. I'd say they are like #2 or #3, but probably #4 in reality. Back in historical times I'd be on track with you, but those other fish that are larger now, well just like the wels they were larger back then too. Overfishing and crappy management has led to all their decline. I've seen one pic of a mekong catfish over 200 kilos, and video of a Piraiba, and pics of several others at the 150 kilo mark. Also Arapaima gigas grows to 450cm and around 200 kilos, there's also giant freshwater stingrays which are believed to get more than 400 kilos, and alligator gar at 305 cm and more than 140 kilos. The list goes on with several others, but that's not important I just don't think that the wels can claim the title of worlds largest freshwater fish when there's already been a mekong catfish caught that wieghed in at over 250 kilos, and they are published at over 300 cm and more than 350 kilos. the max published weight for siluris glanis is 300 kilos. That puts then in direct contention for the title, but if the giant freshwater stingray of cambodia I believe gets as big as they say it won't matter cause it dwarfs both Himantura chaophraya max published wieght is 600 kilos at 240 cm. Just thought I would throw out some competition for the wels, but you never know what might be caught next! I do believe that wels is huge, and is the second largest catfish in fresh water to say the least, and would love to keep one in my pond one day! lol