Cripps isn't a butcher and he isn't selling food, he's selling functional resources: skins, hides, horns, rendered fat and so on. He won't take any meat or fish you have in your inventory, so we suggest taking it to a normal butcher's shop and selling it there, assuming you don't want to cook it yourself.

What do I do with fish in RDO?

Fishing can be done manually or through the use of a fishing rod. When a fish is caught, the player may cook a fish (to restore health, stamina, or Dead Eye cores), donate it to the camp, or sell it for profit.

How do you donate fish in rdr2?

Click the donate button and as long as your horse is in camp you can turn them in right there. The same thing goes with hides, turn them into Pearson right there. If you have fish or animal parts you can donate them directly at that station as well.