The future of fish

We all know by now that cod and haddock have had their chips. But what exactly are these strange new fish we're told we should be eating? And what on earth do they taste like?

We are rightly being urged to broaden our taste in fish beyond a handful of familiar species, but it seems unlikely that the geoduck clam will ever become a staple on the British dinner table. "Good grief! What on earth are those?" yelped my wife when she laid eyes on the dozen I bought back from Billingsgate Fish Market in east London. "Chris! One's moving! It's expanding! I think you're going to be eating those by yourself." This was a shame because the geoduck (pronounced "gooey-duck", it derives from a word meaning "dig deep" in the language of the Nisqually tribe of north-west America) is regarded as a delicacy in some Asian cuisines. Diver-caught in Scotland, my geoducks had oval shells 4-5 inches in length, held tight shut in rubber-band bondage. At one end of each bivalve, a thick, cylindrical siphon emerged from between the shells. Around four inches in length, it was undeniably, even alarmingly phallic. Cutting off the tumescent siphon and skinning it is one of the more disturbing culinary activities I've ever engaged in, calling for a good deal of disassociation. But the anthropomorphic connotations declined as I sliced the siphon into a pile of fleshy rings. Its transformation into sashimi, served with soy sauce and wasabi horseradish, would surely placate my unwilling partner in gastronomic adventure. "Darling, supper's ready!"

I acquired the geoducks at 6am that morning from a Billingsgate trader called Bard Shellfish. "Geoducks are also called sandgapers, otter shells [they're smashed open by sea otters], soft shell clams and piss clams. You can squirt people with them," said Chris Leftwich,

Chief Inspector of the Fishmongers' Company, which retains responsibility for ensuring produce is shipshape and ozone-fresh at Billingsgate. "They can live to 150 years old. Living deep in the sand, they can grow to 15lbs with a siphon that is a metre in length." (For confirmation, look up "geoduck" on Google images.)

"They're very hard to get hold of," said shellfish dealer Ben Bard. "Mostly bought by Chinese and Japanese restaurants." But not all Asian cuisines utilise the geoduck, as I discovered when I asked Joe Jung, a buyer for the Korean restaurant Ran, if he was fond of them. He looked aghast. "No, I don't eat them," he replied with a slight shudder. "They look funny."

With around 40-odd merchants trading cheek-by-jowl, Billingsgate is the largest inland fish market in Britain. It is also the oldest market in London. Records from 1016 reveal that sailing boats were charged a penny to dock at Billingsgate, but the market may be much older than that. (The name may derive from Belinus, a Celtic god.) In recent years, Billingsgate has experienced a change arguably more radical than when it moved in 1982 from its ancient premises near London Bridge to its present home, an anonymous box in the shadow of Canary Wharf. At that time, it was almost entirely trading in the home-grown varieties extolled in the cries recorded by the Victorian social observer Henry Mayhew when he visited Billingsgate in the 1860s: "Ha-a-an' some cod! Best in the market!" "Fine soles, oy, oy, oy!" "Hullo, hullo here! Beautiful lobsters, good and cheap." Though familiar species are still sold in profusion at Billingsgate – one-third of all the fresh fish sold there is salmon – a remarkable variety of exotic produce has appeared on some stalls. More than 140 aquatic species from all over the world now find their way to the market.

"There's a beautiful red bream from Oman and red mullet, like ours but much bigger, from Brazil," Leftwich pointed out, while we strolled the watery aisles. "That's kingfish from the Indian Ocean. Halfway between a mackerel and a tuna, it is one of the fastest fish in the seas. That one is South African hake, caught on a lone line. The big red fish is bourgeois snapper from the Seychelles." He pointed out a shoal of fleshy fish with dark, vertical stripes. "Fresh tilapia, the second most farmed fish in the world. In excess of 3.2 million tons are grown each year. Since our total North Sea fish quota is 30,000 tons, you can see this is quite a lot." A bulky, bland fish that is a mainstay of African and, increasingly, American cuisine, tilapia cooks well with spices. Jerk tilapia is a favourite in Jamaica.

After years of steadily declining turnover, sales from Billingsgate began to enjoy a steady revival around seven years ago, largely due to ethnic customers willing to buy fish at the crack of dawn. "They tend to be market-oriented people," explained Leftwich. "And they know much more about fish, particularly how to deal with whole fish, than the indigenous population. On Saturdays, the place is jammed solid." Open Tuesday to Saturday, Billingsgate welcomes retail customers after 5am, but it is closed by 8am. The fish sold there is very fresh and often remarkable value, though traders tend not to sell small quantities. Sometimes they will sell a kilo, but three or more kilos is more common. Also the fish are sold whole, so you have to be prepared to clean and gut your purchases.

t the stall of J Bennett, salesman Andy Smith held aloft a huge brown grouper known in the Middle East as hamoor. "In Dubai, they sell it battered like fish and chips. Line-caught, it costs £6 a kilo. This fish will weigh about seven kilos, but we do sell fillets in vacuum packs for about a tenner." Is it good? "Well, actually, I prefer not to eat it." At the stall of a trader called Ocean Central, a huge octopus filled a plastic case with swirls of tentacles. "That's an import because it has a double row of suckers – our native octopus has one row," said Leftwich. "This fish from Senegal is the doctor or surgeon fish, so-called because of the scalpel-like barb that it can extend from each side." A row of parrot fish, as vividly polychrome as their namesakes, reminded me that when I was snorkelling in the Caribbean I heard them noisily munching coral. "They're really after the algae that goes on coral, but they're devastating to reefs."

A stall called Indo-Lanka was crowded with mud crabs (described as "excellent" in Alan Davidson's Seafood of South-East Asia) at £10 a kilo and blue swimming crabs from the Indian Ocean at £5.50 a kilo, but I went for a kilo of silvery anchovies for a fiver. The vast, bright-red fish on the slab at Polydor Seafood was a strawberry grouper. Alongside was a shoal of white pomfrets, some of the finest eating to come out of the Indian Ocean. "£7.50 a kilo but you have to buy three kilos – well, maybe two," said the dealer Serkan Tencrere. Indicating a triangular, silvery fish, Leftwich explained, "That one is moonfish, a member of the trevally family."

"It's also known as the lookdown or Mussolini fish," added Tencrene. Cartoon imperious with upthrust jaw, it is described as "delicious" by Davidson.

Leftwich mused on rarities that occasionally make an appearance at Billingsgate. "One of the most interesting is the ribbon or scabbard fish, which can grow up to 6ft long." I saw the dramatic silvery flanks of this creature (Davidson: "An excellent fish") in the market at Lisbon, but, sadly, have never tasted it. Leftwich described an occasional arrival at Billingsgate known as the sunfish or opah: "They can be massive. They just float around in the water." In 1971, Jane Grigson came across a 9-stone specimen in a fish and chip shop in Swindon. "A large fish of curves and perfect beauty of colour," she wrote. "Up to 6ft long ... one of the best fish it's possible to eat." She described it as being akin to salmon but "less fishy" and "more meaty". I felt less regret at missing the escolar. "It is a great delicacy in South Africa," said Leftwich. "But it has a waxy ester below the surface of the skin that causes spontaneous diarrhoea. People who ate it in the belief that it was sea bass were taken ill. It is a delicious fish to eat but generally it is only consumed in small quantities and well trimmed. We sell it as frozen steaks."

Still, I pulled in a pretty impressive trawl from Billingsgate. Along with my kilo of Indian Ocean anchovies, I got a doctor fish, a moonfish, a pomfret and some homegrown treats in the form of razor clams, spiky sea-urchins, an ink-drenched cuttlefish and the X-rated geoducks, lolling in tumescent splendour like bivalve porn stars.

J Jackson, director of the Billingsgate Seafood Training School and co-author of Leith's Fish Bible, briskly accomplished the cleaning of my catch. "The pomfret will need gutting," she said, peering round this plumpish, near-circular creature. "The guts are going to be ... here! As long as you can see the anal vent, you can find the guts." She said that most fish were fairly easy to deal with "as long as you get rid of the head and gills, the guts and the bloodline you'll be OK. I tend to cook fish on the bone. It's tastier, like meat on the bone." Her first step with the doctor fish was to snip off the fearsome scalpels.

Declaring that pomfret was "one of my real favourites", C J rubbished some of the exotica at Billingsgate: "Rabbit fish is awful. Parrot fish is very beautiful but tasteless. It should be left on the reef." She was very much in favour of my cuttlefish acquisition. "I absolutely love it. This is for me the new squid. In this country it is often used for bait – to my mind completely wasteful." She energetically eviscerated the inky cephalopod. "You cut off the tentacles below the eye. Then you get rid of the beak. The tentacles can sometimes be a little bit tough, but the body has a really sweet seafood flavour. You get rid of the skin by putting your thumb underneath and it comes off like a glove. People are scared of cuttlefish – but look at that. Absolutely lovely."

Back home, I started work on the anchovies. They proved a bit harder to deal with than their Mediterranean cousins. For each tiny fish, you had to split open the stomach with your thumb, remove the backbone, then take off the head and tail and a spiky dorsal fin. The result was two gorgeous fillets decorated with twin stripes of silver like the chrome trim on a '59 Chevy. Unfortunately, I had 70-odd anchovies to tackle, which took well over an hour. "Time well spent," said my wife when I presented her with some fillets sautéed in butter. "Mmm, they taste so good. They have a lovely, buttery, caramelised flavour that doesn't really taste of fish." The fillets were also excellent after being marinaded overnight in white wine vinegar and a little salt and eaten as a sort of ceviche with olive oil, slivers of garlic, chopped parsley and lemon zest.

Mrs W happily tucked into the sea urchins, which are usually eaten raw. They have a delicious taste of oceanic freshness, akin to oysters, but more profound. I might also have served the razor clams live, but my wife was adamant against the idea. "You have to cook them. When you made me eat them live, they were wriggling round the plate." Even when they were steamed open and grilled with garlic butter, she had mixed feelings. "My last one was too big. It's made me feel queasy. The smaller one I had before was more girly, lovely and sweet." The grilled cuttlefish was almost as sweet, but more succulent and satisfying. The surgeon fish was a disappointment – tasteless and boney. Mussolini was creamy and delicate, though not as fleshy as its infamous namesake. Firm and sweet, the flesh of the pomfret was reminiscent of lemon sole. It also fell off the bone like a flat fish, though it isn't. This Indian Ocean non-pareil is worth the trip to Billingsgate in itself. But should you get some geoducks at the same time? We had the sliced siphon and meat from inside both as sashimi and steamed in white wine. I thought it was OK in a chewy sort of way, but scarcely worth the trauma involved in its preparation. My wife was less ambivalent. "It was disgusting."

"So you wouldn't like it again?"

"NOOOO!"

Where's the catch? The A-Z of sustainable fish, by Sophie Morris

A is for Abalone – seek out the farmed version of these snail-like shellfish often served at lavish Chinese wedding banquets.

B is for Basa – or Vietnamese catfish. A light, flaky white fish native to the Mekong river delta and available all year round.

C is for Crab – pot-caught crab is about as sustainable as it gets (but remember to avoid anything caught by dredge, net or trawl).

D is for Dab – smallest of the flatfish and cheaper than halibut or turbot. Avoid during the April to June breeding season.

E is for English Sardines – rather than European ones as heavy fishing in the Med has led to shortages in parts of Spain.

F is for Flounder – cook thin ones as you would a Dover sole and treat the thicker specimens like turbot. Avoid young fish.

G is for Gurnard – Hugh Fearnley-Whittingstall suggests pot-roasting with leeks, celeriac and a slosh of white wine.

H is for Halibut – Pacific stocks are well-managed and several US fisheries are certified by the Marine Stewardship Council.

I is for Icefish – similar to seabass and increasingly available in British fishmongers.

J is for Jonah Crab – harvested from the carefully managed fisheries of Maine/Rhode Island. Prized for their meaty claws.

K is for King Mackerel – most of these silver-green fish from the Atlantic and Gulf of Mexico are caught with hook and line.

L is for Lythe – aka Pollock, and a great alternative to cod. Try to buy line-caught, and avoid between January and April.

M is for Mahi Mahi – ugly fish, lovely Hawaiian name. Fished in selective artisanal fisheries so stocks should remain strong.

N is for New Zealand Hoki – ready meals giant Findus use this as a cod substitute.

O is for Oyster – natural oyster beds that have been over-fished are now being regenerated by farming with a variety of species.

P is for Pilchards – best caught in traditional drift or ring nets off the coast of Cornwall, and served very fresh, grilled or barbecued.

Q is for Quoy Fish - a species of parrotfish found in the coral reefs of the Pacific and considered a delicacy across much of Asia.

R is for Red Mullet – but do make sure you avoid anything from the Med, where intensive fishing has left the species under threat.

S is for Salmon – buy only farmed organic, Freedom Foods- certified, or Pacific salmon from Alaska, which is MSC certified.

T is for Trout – brown or sea trout organically farmed and produced to high welfare standards ticks a lot of eco boxes.

U is for Urchins – eaten in Asia and the Med, red and green sea urchins are popular varieties.

V is for Vietnamese Clams – hand-gathered clams from small fisheries along the Mekong delta have little local eco impact.

W is for Whiting – this small fish, a member of the cod family, is ideal for making fishcakes.

X is for the X-rated Geoduck – strange-looking clams, diver-caught in Scotland. A delicacy in some Far Eastern restaurants

Y is for Yellowfin Tuna – this fast-growing species can withstand intensive fishing.

Z is for Zebra Tilapia – a good West African alternative to traditional North Sea fish.