Good bait for Bluetail and Bastore Bream/Mercanbaligi.
NPCs for 54-64 gil, which means a stack (now of 99) is immediately worth 5436-6336. Don't sell these on the AH for less than that...
These can be bought from Babubu at the Windy fishing guild for ~213 each, or 21,087 gil for a stack of 99.
Support your local crafters (typically starting cooks) and buy this for a price that doesn't make this a loss synth (so, add the price of 1 Bastore Sardine and 1 wind crystal, then multiply by 50). You may then find it up on the auction house more often.