Fishmongers were once common on Britain’s high streets. Nowadays you are more likely to find fresh fish in supermarkets, huddled behind clingfilm and almost odourless. As a young teenager brought up in Highgate Village, as it was then known, I took for granted the presence of certain traditional shopkeepers: Mrs Gay, whose sprawling greengrocer’s shop had not yet ventured to stock garlic or pimentos – to find these, one had to trek to the nearest Greek Cypriot store down in Archway; a flour merchant, where you could buy wholemeal flour (a rarity in those days); Atkins, the pork butcher, who used to slaughter his pigs in his back yard and made excellent English-style sausages with ultra-thin pork casings that could be crisped up in the oven; and his brother, fishmonger Atkins, who was so determined to keep his wares fresh that he displayed very little on his thick marble slabs, preferring to stash most of it away in a cold store. His rival fishmonger across the road, whose name I’m happy to say has slipped my mind, exhaled such a high concentration of ammonia that it could be smelt within a radius of 50 yards or so. The dozens of different varieties of fish displayed outside would lie there disconsolately, many of them in the sun, attracting crowds of curious customers. On one occasion, my mother was so enraged by the stench that she collared the fishmonger in question and gave him a piece of her mind: ‘Those same herrings have been on display there for the last three days. Look at their sunken eyes! You ought to be ashamed of yourself.’ In those days, it didn’t do to complain in public. The other customers shuffled sheepishly away.

Let us now flash forward to the present day and the wonderful food market held weekly in my neighbouring little town of Maurs, in the Cantal. One of the most popular stalls there, and the one with the longest queues, is run by a fishmonger and his wife who drive every week all the way from La Rochelle on the Atlantic coast to Maurs (a round trip of 900km). The neatly arranged rows of fish smell of nothing but the sea. One day recently, I noticed the presence of an odd-looking snub-nosed, tiny-mouthed fish in the shape of a turbot, but with one eye on either side of its head (the turbot’s eyes are both on the same side, as in most flatfish). It sported a handwritten price tag (all the other labels were printed), giving its name as baliste and indicating its very reasonable cost of €9 a kilo. I told the fishmonger I would like to try it and asked him to gut it for me. He strongly recommended the resulting fillets, which he described as reminiscent of cod, though slightly sweeter. The fish was indeed excellent.

Not surprisingly, this whetted my curiosity. I consulted Alan Davidson’s books, North Atlantic Sea Food and Mediterranean Sea Food. Both of them listed baliste (or Balista capriscus, a variety of triggerfish), and described it as very good to eat. I dug a little deeper. When I telephoned a number of big Paris fishmongers, they all said that they did not often stock the fish, because the fishermen who caught baliste tended to keep it for themselves. My Maurs fishmonger, who was clearly well informed, told me that in recent years the baliste, a migratory fish that is attracted by a warmer environment, had tended to be caught farther and farther north because of global warming. I consulted a specialised website, glaucus.org.uk, which revealed that the fish used to be confined to the Mediterranean and the North African coast, but was now frequently caught or sighted by divers off the Welsh coast and the Channel.

I still needed to solve one or two remaining mysteries: triggerfish are described as preying on winkles, whelks, mussels and even oysters. This they can do because of their razor-like teeth (they have been likened to piranhas), which enable them to ‘saw’ through quite thick shells. But then how do they manage to cope with the size of their prey, most of which is larger than their tiny fleshy mouths. The answer I found in a website that provided a technical description of the triggerfish: it noted that it possesses ‘protractile’ jaws, which enable it to slide its jawbones open to a much larger aperture than would seem possible at first sight. The same website explained the origin of the name ‘triggerfish’: if threatened, the fish can work its way into a protective crevice and wedge itself in place by erecting its front dorsal spine. It is difficult to dislodge from that position. The second spine is connected to the first and when this is depressed it triggers the unlocking of the first spine. Another interesting characteristic of the triggerfish is that it can swivel its eyes independently, like those of a chameleon.

Glaucus.org.uk also includes a video of a triggerfish swimming among a group of divers, as though curious to discover the identity of the large creatures swimming around it in flippers. Triggerfish are so ‘trusting’ (to use an ornithologist’s term) that there have been reports of people feeding them by hand in the wild and even stroking them. They are greatly appreciated by aquarium owners, who have observed various curious behaviours on the part of the fish: they recognise their keepers when approached and ‘beg’ for food; they propel themselves through the water by ‘sculling’, i.e. relying solely on their soft anal and dorsal fins, but if a sudden burst of speed is required they will use rapid sweeps of their tail; they resort to ‘hydraulic jetting’, which involves directing a jet of water out of their mouths into the sand to uncover buried prey; there are triggerfishes that like to ‘redecorate’ their aquarium, taking pieces of decor in their mouths and moving them elsewhere in the tank. Too bad if this smacks of anthropomorphism, a characteristic shared by most pet lovers – and aquarium owners.

By the way, my Maurs fishmonger had insisted on skinning as well as gutting my baliste. This, he explained, was because its skin is extremely tough, even to the point of blunting the knives of professionals who fillet it (as seen on YouTube). He let me feel its skin, which was startlingly abrasive, almost sandpaperlike. He told me that Portuguese fishermen not only enjoy eating baliste but use its skin to scrape barnacles off their boats. A versatile creature indeed!