You can't sell fish. In the medium term, you can use meat to upgrade your health and speed plus the maximum health. Fish with acceleration must not be sold. If the meat is in the back, the duke can help you cook. Never sell it. If you find a bluebird, it will drop the high-grade meat. When the plot progress is red, the cooking system will be unlocked. These meats will be used, and the menu has various permanent additions. So fish can't be sold in Resident Evil 8 Acquisition Bank.