Hi,
Here in Thailand I can tell you a few facts:-
1. We (Saim Fishing Tours) held(or still hold although a submission is now in for a bigger fish) the world record for the Arapaima for a few months at 86kgs the fish measured 72 inches (these figures are approx becuase I dont have paperwork to hand as I am typing this.
2. We have captured Arapaima more than twice the size of the one we submitted as a record, and I would say it was around 50% longer
3.We also have unsubstantiated claims, yet from credible people here in Thailand of fish to 12ft long, and fish weighing 224kg from different sources. I am conifident of the 224kg but not confident of the claim of 12ft.
4. There are those that believe that Bungsamran fishing park in Bangkok holds several specimens that could be in the 250kg to 300kg range. I dont think these fish would go longer than 9ft/10ft though.
Personally I think one of the problems is that too many people over estimate weights in the first place. If you compare the 2.63 Mtr fish at an estimated wieght of 185kg and then compare the one we captured in January this year which we know for a fact was at least 17yrs old and we put an absolute ceiling on it of 9ft and 200kgs (more likely 185kgs) we dont see any comparison with the much younger fish of 2.63mtrs that others here are claiming is "verifiable". Its certainly know more verifable than those we have captured. What gives our clients fish away as a bigger specimen is the girth and depth, but also the tell tale signs of a fully mature fish which can be seen in the scale colouration, the red flash on the scales reaching to within 5 scales of the top of the specimens head.
5. If people do not weight and measure fish accurately we will will never answer these questions which is perhaps why this thread runs on and on, its difficult to weigh and measure a large fish accurately and release the specimen safely, which is why so many fish out of Thailand have estimated weights placed on them. They come from catch and release fishing venues and most anglers want to return them alive. I stand by the suggestion that sooner or later Thailand will throw up a freak and its going to be 9ft/10ft long and in the 250kg to 300kg range. Far bigger than any Arapaima from the wild, but still not the biggest freshwater fish, not by a mile.