There should be no problem. It was the same when my family cooked it. It is estimated that there was a great struggle after fishing, which led to muscle filling and then death, and the blood could not be scattered, so the color of the meat was red. Even for other fish, the color on the side will be darker when cooked. Because the sole is very thin, the congestion effect may be more obvious.

Like the kind of fish that is killed and bled while alive or the fish that is frozen immediately, this will not happen ...

Fish are usually like this, their eyes have not turned red and sunken, and their scales (including "scaleless fish" such as Spanish mackerel) have not fallen off or are very weak. Generally, they are relatively fresh, or they are relatively fresh before refrigeration and freezing processing.