Many types of fish are delicate and tender, so you want to avoid overcooking them. The best way to tell if your fish is done is by testing it with a fork at an angle, at the thickest point, and twist gently. The fish will flake easily when it’s done and it will lose its translucent or raw appearance.
A good rule of thumb is to cook the fish to an internal temperature of 140-145 degrees. Try the 10-minute rule, which says you should measure the fish at its thickest point, and cook it for 10 minutes per inch, turning halfway through the cooking time.