They are seasonal as the rainy season limits collection of them due to high waters. These are all hand caught fish remember and not farmed like our widely distributed colorful domestics. And along with hand fishing comes fishing regulations and of course suppliers grading their fish and that cuts down the number of quality fish making it to the market. Most of the amazing wilds go towards asia because they will pay a LARGE amount more than us here in the states which again will cut down the numbers you see coming in here.
Up until a matter of a few years ago the states really had no constant good supplier selling/importing here. I think popularity for them is growing but because of the limited number coming in each season and a higher demand its tougher to get than any domestic. The interest in wilds is higher than ever IMO.
And just because its a wild topic who doesn't love photos of them.....