Choosing your fish is probably the most important and crucial part of your intended dish. Without good quality fresh fish, your dish will be ruined before you even start and decide on the fish recipes you will be following.
The first advice would be to not use anything frozen. The best chefs creating the most delicious dishes do not use anything frozen, tinned, bottled or preserved in any way unless they have either done it themselves or it is absolutely necessary. There are a lot of dishes where frozen fish is definitely unsuitable. Mousselines are a prime example of this. The freezing of fish seems to break down the gluten content of the meat and therefore a good binding of egg white and cream cannot be achieved.
Have you ever noticed how much ice you get with frozen fish (or glaze as the manufacturers call it!)? Prawns and scallops are both heavily glazed items. When defrosted, see how much smaller, limp and tired looking they are compared to those lovely, plump, shiny examples of their species sold fresh.
We all know that the majority of fish caught is frozen at sea when it is at its best. This is, of course, true. However, it is equally true that a lot of fish landed fresh today finds itself unsold in a few days time and finds its way into a freezer and then, of course, it is sold as frozen. How old was it before it was frozen? In fact, it may even been frozen once already, thawed, then refrozen to extend its shelf life. That glaze on it, is it natural sea slime? Or is it slime from decomposition? This is a little hard hitting and certainly the exception rather than the rule, but do make no apologies for it. After all, it is definitely harder to tell how fresh a fish is when it is frozen!
Now that you do not want to buy frozen fish, how can you tell whether the fresh fish you are looking at is really fresh? Well, most of it is commonsense. A fresh fish looks fresh (obvious, isn’t it?), bright and shiny. An old fish looks dull and lifeless. The first sign is the skin. It should look shiny, have a slight natural slime, and the scales should look bright and fresh. The eyes should be nicely rounded and once again have a good shine, not sunken and dull. The gills should be a bright red. As the fish ages, the gills go very grey and dirty looking. Another way to test for freshness is to press the fish quite firmly with your forefinger. If it leaves a mark that will not go away, then the fish is old. If it springs back and leaves no mark, you have a good fish. There is, of course, yet another way to test for freshness. Just bend down so that your nose is about 5 cm/2 inches away from the victim and inhale deeply. Believe me, if that poor fish is bad you will know about it long before you get that close!