make caviar a kinda rare butchering product from fish like eyeballs but maybe thats like a decent curiosity or full of hecka dank feps like a bunch of +2 psy and +2 will or something so it has multiple uses and also gives something to hope for with fishing
if you really wanted to be adventurous you could do something like implement different kinds of caviar for the big fish (e.g. sturgeon and salmon) or give caviar units like opium and have higher quality fish give more caviar or make certain hidden breeding grounds more likely to produce caviar-laden fish
also swim bladders for isinglass to improve beer quality or speed up production (historically using sturgeon)
#makefishinggreatforthefirsttime