Rather smelly and fishy.
The item id for Amberjack Cooked in unturned is 6607. You can use this ID with the commands below to spawn the item, give it to a player or buy it on a modded economy server.
Useable: Consumeable
Size_X: 3
Size_Y: 2
Size_Z: 0.42
Food: 40
Health: 10
Blueprints: 1
Blueprint_0_Type: Supply
Blueprint_0_Supply_0_ID: 6606
Blueprint_0_Supply_0_Amount: 1
Blueprint_0_Level: 1
Blueprint_0_Skill: Cook
Blueprint_0_Build: 27
Blueprint_0_Map: Easter