If the gills and jaw of the fish is light pink, or light red (depending on the species) and its flesh is close the body, you may be sure it is fresh. Additional features of fresh fish are: convex, light and shiny eyes, and the pliant meat. Once the gills are whitened, or covered with dark brown spots, eyes become covered with mucus and fallen in, fish is definitely no longer suitable for consumption. Other features which may inform us about this include shrunken pupils, sticky, yellow mucus and an unpleasant smell of the meat.