Fresh or frozen fish: an honest answer

Fresh and frozen are both good, and the honest answer is that neither wins outright. Frozen fish is often excellent, sometimes better than a chilled fillet that has been sitting in a cabinet for four days, because freezing stops the clock. A chilled counter gives you things a freezer cannot: whole fish you can look in the eye, a cut made to the thickness you asked for and the species that only ever turn up in small quantities. This page explains what actually happens to fish in each case, so you can choose on the facts.

What does "fresh fish" actually mean?

Very little, legally. "Fresh" is not a graded term in UK retail and it carries no time guarantee. It means the fish has not been frozen. It does not tell you when the fish came out of the water, how it was handled or how many days it has spent on ice before it reached you.

The clock on a chilled fish starts at the catch rather than at the till. A white fish held properly at close to 0C on ice stays in good eating condition for several days after landing, and the countdown runs the whole time it is in a lorry, a market, a chill room and a display case. Two fillets labelled fresh on the same day can be four days apart in age. This is why a fishmonger judges by eyes, gills, flesh and smell rather than by a label. Our guide to how to tell if fish is fresh covers the five checks.

What does freezing do to fish?

Freezing turns the water inside the muscle into ice, and the size of the ice crystals decides how much damage is done. Frozen slowly, the water forms large crystals that push through cell walls, so when the fish thaws the cells leak and you get pale liquid in the tray and a drier, softer texture. Frozen very fast, the crystals stay small and the cell structure survives largely intact, and the thawed fish behaves close to a chilled one.

This is the whole argument in one sentence. Fast freezing is good for fish. Slow freezing is not. A commercial plate or blast freezer takes a fillet through the danger zone in minutes. A domestic freezer takes hours.

Freezing does not stop everything. At household temperatures the fat in fish continues to oxidise slowly, which is what makes long-stored oily fish taste stale, and the proteins gradually denature, which is what makes it dry. Both are slow. Neither is a safety problem. They are quality problems that grow with months in storage.

Is frozen at sea fish good?

Yes. This is where the argument for frozen holds up plainly. Fish frozen at sea is processed and put through a plate freezer on the vessel within hours of coming aboard, long before any chilled fish could reach a shop. It is common for cod and haddock from northern waters, where the fishing grounds are days from port. If the choice is a frozen at sea fillet against a chilled fillet that has crossed a continent, the frozen one may well be the fresher piece of fish in every sense except the label.

Prawns show this plainly. Almost all warm water prawns sold in the UK were frozen shortly after harvest, including the ones sitting on ice at a counter, which have been thawed for display. Squid and many scallops follow the same route. Nobody is hiding anything. It is simply how those products travel.

When is frozen the better choice?

• You are not cooking it today. A frozen fillet on Tuesday for a Saturday dinner is in better condition than a chilled one bought on Tuesday and left in the fridge.
• You want a species that is out of season or far away. Freezing is what makes a fish from distant grounds available at all.
• You want it consistent. Frozen portions are cut to a fixed weight, so cooking times repeat exactly. That matters for batch cooking and for feeding children on a schedule.
• You waste food. A freezer means you cook fish when you want to rather than when it is about to turn. This argument for frozen is rarely made and it carries more weight than any other.
• You are preparing it raw or lightly cured. Freezing is the food safety step for that, and the rules are set out on our page about eating fish raw at home.
• You are cooking from frozen. Thin white fillets go straight from the freezer to a hot oven and cook well. Our note on cooking fish from frozen covers the timings.

What can a counter do that a freezer cannot?

This is the other half of the answer, and it is about form rather than freshness.

• You can see the whole fish. A frozen fillet has already had the eyes, the gills and the skin taken away, which are the three clearest signals of condition. On a slab you assess the fish yourself before anyone cuts it.
• It is cut to your dish. A thick shoulder piece for batter, a thin tail piece for a quick pan, four equal portions for a dinner party, on the bone for a whole roast, off the bone for a pie. A frozen pack comes in one shape and you cook around it.
• You choose by eye, on the day. You buy the fish that looks right this morning rather than the fish you planned to buy last week. If the turbot is in better condition than the brill, you switch.
• You get the by-products. Bones and heads for stock, roe, trimmings, a crab shell for dressing. Those come free with a whole fish and never come with a frozen fillet.
• You get the species that never make a product line. Gurnard, megrim, dabs, John Dory, whatever came up in small numbers. Volumes too small to freeze and pack commercially reach a counter easily.
• Nothing has to be thawed. No planning, no drip tray, no forgetting.
• You can ask. Someone who handled the fish that morning will tell you what is in good condition and what to do with it.

How can I tell whether fish has been frozen?

Ask. A counter should answer plainly, and the answer is often yes for prawns, squid and some scallops.

There are also signals. Thawed fillets tend to sit in a small pool of milky liquid, the flesh gapes slightly between the flakes and the surface has lost its gloss. Frozen at sea packs usually say so on the front, since it is a selling point. Fish that has been frozen and defrosted before sale generally has to carry the word "defrosted" in its name under UK food information rules, with limited exceptions, including where freezing is a necessary technological step. Retailers do not always get this right, which is another reason to ask rather than to read.

One rule matters more than any of this: do not refreeze fish that has been thawed, unless you cook it first. The second freeze does the damage the first one avoided.

How long does frozen fish keep?

At a steady -18C, white fish such as cod, haddock and hake typically holds good quality for around six to eight months. Oily fish such as mackerel, salmon and sardines typically holds for around three months, because the fat is what oxidises. Shellfish sits in between. These are quality windows rather than safety limits, since fish kept frozen throughout stays safe well beyond them and simply tastes progressively duller.

Two things extend it. Wrap tightly so no air touches the surface, since freezer burn is dehydration. Keep the freezer closed and cold, because temperature swings grow the ice crystals you were trying to avoid.

What is the correct way to thaw fish?

Slowly, cold and with the liquid drained away. Put the fish on a rack over a tray, cover it loosely and leave it in the fridge overnight. The rack matters, since fish sitting in its own thaw water goes soft. Pat it dry before it meets the pan, because surface water stops skin crisping.

Do not thaw fish in warm water or on a worktop. The outside warms into bacterial territory long before the middle gives up its ice. If you have forgotten and it is thin, cook it from frozen instead and add roughly half again to the cooking time.

So which should I buy?

Both, for different jobs. Buy chilled from a counter when you are cooking within a day or two, when you want a whole fish, a particular cut or a species you cannot get in a packet and when you want advice on what is in good condition today. Buy frozen when you are stocking a freezer, when consistency and portion control matter, when the species you want is far away or out of season, when you would otherwise throw fish away and when you are preparing it raw.

Fresh against frozen is the wrong question. The useful questions are how the fish was handled, how quickly it was handled and how you want to cook it.

How we work at From The Sea

We have run a fish counter on Barnes High Street since 1972. We buy at Billingsgate through the week and direct from Cornwall, and the fish comes into the shop whole wherever we can, so it can be assessed on the slab and cut when you ask for it. Filleting, skinning, pin-boning, scaling, gutting, portioning, shucking and crab picking are done by hand in the shop at no extra charge. If you want to know what came in and what is in good condition today, call the shop or ask at the counter. You can read how we buy or come and look at the slab.