At 646LB is this Mekong Giant Catfish the largest freshwater fish in the world?

From SiamFishingTours.com:

 

At Nearly nine feet long (2.7 meters) and as big as a grizzly bear, a huge catfish caught in northern Thailand may be the largest freshwater fish ever recorded. Although there are many claims and rumours about the worlds largest freshwater specimens, especially  from misguided anglers. However, in the eyes of scientist's the Mekong Giant Catfish has taken pole position with the recorded capture of this huge 646LB specimen by local fishermen in 2005. Many anglers over look the fact that some larger fish that can be caught in the worlds rivers, such as Sturgeon, migrate between river and sea, and therefore not considered to be freshwater species in the true sense of the word.