The most important thing when making sushi is that the fish is really fresh. Almost any finfish can be eaten raw if perfectly fresh, but it is recommended that it should be frozen before eaten. This is to eliminate the risk of parasites. Eel and octopus is always cooked. Its body should be stiff and the meat firm when touched.
Most fresh fish have clear eyes.
The tail should not be dried out or curled up at the end. It should not smell fishy. The scales on a fresh fish should adhere tightly. The gills should be cherry-red and should not have any white slime. Most shellfish should have tightly closed shells.