We seem to be on the wrong thread for this topic Dirk, and i hate to give Bops the problems of shifting it to the right spot, but here goes.
Your ideas are valid Dirk, but i have some spanners to throw in.
I just hope that we haven't really lost any of the larger fish.
One thing i can say is that in the December of 2004 there were very big fish around, and all of the old gold and silver variety, i did not catch a single bluefin among the 14 fish taken in 2 days at Hiara, and that was the dry year that Terry was talking about, but still the goldies were around later that year (I did fish in May of 2004 in peak summer), we could sit on our bums in the middle of the rapids above Galibori camp and fish but there were no fish taken, the water was the lowest i have ever seen it. We could walk across the river from Hiara to the temple on the other bank where Thambi used to live without having to swim, the water was that low, but the big fish were back in December that year.
2005 saw some of the biggest rains that we have seen in 50 years and if i am right MM had some good fish around the 50 mark after the monsoons, but thereafter in 2006 things have changed with only the smaller bluefin being caught on a regular basis, with a few small goldies thrown in.
I will admit though that the bluefin are pretty aggressive fish, and even the small ones can strip your reel of 40 lb mono in a matter of seconds. However i still don't think we know the real reason for the dissapearence of many of the monsters.
I would like to look closely at the fish that JB caught last year in Nov & Dec to see which variety they were.