The definition of fresh fish is that is has been cooled down, but not frozen or otherwise processed or prepared before reaching the fish counter. To evaluate the quality of the fish there are some simple checks you can make:
Fresh fish should have shiny skin. If fish has been stored too long, its skin has a duller appearance.
The eyes should be clear, shiny and slightly protruding. Again, a fish that is approaching its saleable expiry date will have eyes which are duller, grey coloured, and slightly sunken in the head.
The gills of fresh fish should have a uniform attractive red colour with clearly marked rays. Fish that have been displayed for too long have gills that are paler at the edges and somewhat contracted.
Good quality fish should have a mild fresh smell. Fish that has a strong distinctive smell has been stored for too long.
Firmness is also a signature of good quality. The flesh should cling to the bones, and be elastic to the touch. Depressing the flesh with your finger is a good test. With fresh fish, you can expect the fish to spring back to its original shape, leaving no indentation.