Oyster

These come up while fishing desert water, and there is no situation where holding on to a sealed one is right. The meat inside is worth more than the unopened item on its own, and the pearl roll sits on top of that for free. Open the whole stack as soon as you are back at base.

Pearls are the reason to keep fishing the desert after your quest fish is handed in. White ones show up often enough to feel routine and pink ones almost never do, and none of it responds to luck, so potions, ladybugs and a well placed Torch God do nothing for the odds. The only lever you have is opening more oysters.