I'm curious to hear your results. In my experience, this type of fish/food (with buffs) are not really big sellers. This may change with some of the high level cooked items, but I can't speak from experience on that. I think that the demand just isn't high enough to drive prices to make it worthwhile (i.e., profitable enough) to spend the time fishing. My guess would also be that most people that are aware of the buff benefits of certain foods will be the type that take the time to skill up fishing/cooking to get their own. I think what drives the demand for the three main money fish (Oily Blackmouth, Firefin Snapper, Stonescale Eel) is primarily the inherent laziness of some people in acquiring mats needed to make other mats for alchemy. Laziness isn't necessarily the right word, since for some it's simply a matter of money not really being an object and ultimately, for them, it's cheaper to buy mats than to spend the time fishing.
Like I said, though, I'll be interested to see your results.
On another note...scanning through the list of fish (http://wow.allakhazam.com/db/fishing.html?byitem=1), I just remembered that Winter Squid are another decent selling fish. When cooked, the Grilled Squid will restore 874 health and give a 10 Agility boost for 10 minutes. They're harder to come by because there are no Squid schools. But, they do usually sell.
The linked list above is a little clunky with all the other items that you can catch listed, but check through it and look at prices and read what people have commented about them. Note that the huge fish (e.g., 17-pound Catfish, which shows a median price of 90s) are really not used for anything (they are just an off-hand showoff piece, I guess designed for humor) and are unlikely to sell on the AH, despite the prices listed.
Basically, some fish may sell once in a while, but in general Oily Blackmouth, Firefin Snapper, Stonescale Eel, Deviate Fish, and Winter Squid will be the ones for which there is a consistent demand.