Good post. Good question.
I will give you an abridged answer here, for more detailed reading reference the stickies at the top of the Other Characins section.
The reason mid to late 2012 and early 2013 has seen so many oddball ATF coming in is quite simple, really. The traditional supply was all dried up. There was however still a demand. This resulted in the exporters going elsewhere to find their fish. This is the reason we've seen so many of the formerly rarest two species, brevis and tanzaniae, as well as Zambezi vittatus, this past year.
The reason we have seen so few of our traditional vittatus and goliath this past year is because like sashimi said, the geopolitical atmosphere of Africa destabilized. From the middle of 2012 to now, there is a pseudo civil war being fought in the Central African Republic, the country immediately to the north of the Congo. This has fairly well destabilized the region and was responsible for the lack of Congo ATF exports. There was a truce signed, I believe back in January, which is allowing the region to stabilize and exports to start back up. The best season seems to have been missed so goliath and Congo vittatus will likely be very scarce this year, too.
On the subject of tatf vs vatf-
Tatf have been brought in for a long time. They have however been largely misidentified until now. It seems to me that no one really did the homework to find out the diagnostic traits to tell them apart. It was well needed that we did, too, because these fish are
extremely closely related and
extremely similar morphologically. The tanzaniae from the Rufiji and Ruaha watersheds in Tanzania, is directly descended from the vittatus populations in the next major river system to the south: the Zambezi. The tatf is essentially a vatf that has undergone allopatric speciation and is trying its best to be a goliath.
To tell them apart, for a tatf look for a proportionately thicker, cigar shaped body, a proportionately more massive jaw, the second stripe above the lateral line will always be less prominent, the adipose fin will be blue, though in some fish it will be so dark as to appear nearly black, the tail will be lacking in dramatic coloration with just a little dull red or yellow in the tail.
For a vatf, look for a proportionately thinner, football shaped body, a proportionately smaller pointier jaw, the second stripe above the lateral line may rarely be slightly reduced but not as dramatically as the tatf, the adipose fin will be black when large or clear when small, the tail will be vividly colored with reds, oranges and yellows.
Its fair to think of a tanzaniae as something of a color variant vittatus.
Pics:
tatf left, vatf right
vatf top, tatf bottom
tatf
vatf
Should be big ATF, medium Odoe, small Dorado, dinky Aimara.......