Since Brillat-Savarin (1755 - 1826) and his famous "Tell me what you eat and I will tell you what you are" we know that food is intimately related to each culture. As an illustration of this precept, let see how does fish is considered in different countries and especially how do people judge it's freshness :
In France, a fresh fish is judged on his eyes, crystal clear, shining and lively. That's the criteria (most) french consumer use to select their fish at the market.
In Turkey, the gills need to be showed with strong red color to clients in the street markets as a proof of freshness.
In Japan, it's important for the customer to be sure that no one ever touched the fish with its hands, so you can have a look inside the laboratories to check that.
In China, fresh means live. That's why you may choose and catch yourself your fish which will be prepared in front of yourself. (Video taken in A Carrefour Hypermarket in Beijing)
In Colombia, before the arrival of Carrefour (1998), it was difficult to find fresh fish in the supermarkets. You barely could only buy frozen fish. I remembered have seen entire family coming at the inaugural of Carrefour in Girardot to see for the first time fresh fish.
In Spain, Fish is the key factor for consumers to judge the quality of the store, in the same way as French give importance of bread quality or Argentinian to meat.