I've cooked a few types of fish and they are all the "normal" ones you can get at a regular supermarket: salmon, trout, tilapia, cod, mahi mahi, Chilean sea bass, etc. I saw shad in the freezer aisle at Fubonn today, but if the fishing gods would shine upon my pole one day, I could fish a shad out of the Columbia River. I've never had shad or shad roe, but seeing how it is plentiful in the Pacific NW, I passed this by. Also, for a mystery ingredient, because it is a trial 'n' error process, it's an ingredient that is also inexpensive to procure.
I settled upon something called Moonfish. It is quite small and much smaller than a blue gill. This is definitely not of the Hawaiian variety, and is probably more like some freakish thing a fisherman would haul up in the net with other fish and didn't want to throw it away. And for a mere $2 for 1 lb, there are two of these in the package: