Not every fish is edible, there are also poisonous ones. Toad fish (Opsanus Pardus), parrot fish (Sparisoma Viride), hedgehog fish (Balistes Capriscus) are some of the fish with a poisonous flash. It was considered that only sexual organs and digestive organs of those fisher are poisonous, so if you remove those organs fish become edible. However, that theory was proven wrong and now we know that the flash of those fishes stay poisonous even if we give them a good scouring. So, it’s wisest to stick to the old Chinese’s prove: “You should not eat any fish that does not look like fish”. However that may sound, it’s a fact that a very few poisonous fish look normal, usually those fish have something to warn their predators. They can swell up with water or air, or they can have spines rather then scales, or even bony “beak” on their mouth.