Rinse the rock bass under water running from a tap for about three minutes and place it on a flat cutting board. Cut the fish on both sides of the neck with a sharp knife. Cut through the skin by running the knife along the top fin, starting at the front and ending at the back. Turn over the bass and cut through its skin once again by running the knife along the top right side this time.
Once again turn over the fish and cut along the backbone on the left side by running the knife from the front of the fish all the way to the tail. Your knife’s path may be hindered by the ribcage as you approach the tail of the fish. In such a situation, you will have to push the knife through the other side of the fish until you cut all the way through the tail. Do the same with the right side of the fish.
On the left side of the fish be sure to cut out the fillet by slicing through the top of the neck. Cut around the ribcage and along the side by starting at the front and ending at the back. Cut the right side in a similar manner. When you are done, both fillets will be separated from the fish.
Carefully slice in between the meat and the layer of skin from both fillets. Be sure to leave about 1/16 of an inch of meat intact. This will remove a major portion of the dark muscle meat. Although this meat is not harmful and can be eaten, the fish will taste much better when cooked without it.
Discoloured white meat around the fillet edges is in fact fat. Be sure to remove it and the bass will be ready for cooking.