There are many species of fish indigenous to the British Isles. The quotidian brown trout means more to me than any other because there’s nothing I enjoy more than fishing for them or exploring the places that obsession takes me to. After that, and only a fraction after, there’s the Atlantic salmon. Then pike, perch, grayling and sea-bass – I like fishing for all of them. In British rivers or lakes there are also bream and tench, barbel, roach, rudd, dace, chub, bleak, eels, gudgeon, minnow and miller’s thumb. Around the coast there are the various sharks – mako, porbeagle, blue, thresher, whale – as well as the sharklike tope and dogfish; the various species of ray with their beautiful names like cuckoo, sandy, starry and thornback; there are skate, white, common and long-nosed; there’s the ‘gadiforme’ family of cod, haddock, whiting, pollack, hake, coley and ling; there are plaice, sole, monkfish, angler fish, garfish, wrasse, John Dory, mackerel, bream, weeverfish, shad, anchovy, sandeel, conger eel, flounder, dab, mullet (thick-lipped, thin-lipped, golden and grey); there are even sunfish and swordfish and tuna. The list is long.

Amongst all these species of fish, however, there are a handful so culturally embedded that their history is our history. These are the fish I wanted to write about: cod, salmon, herring, eels and the immigrant carp. Every one of these but carp is on a knife-edge of viability.

Cod (I could add haddock, but cod and haddock are so often said in the same breath, caught in the same nets and cooked in the same batter, they can be looked at almost as one entity) are the staple component of our beloved fish and chips, the meal which defines us as a nation. Fish and chips fed the industrial revolution, fish and chips (never rationed) helped us first survive two World Wars. Further back in history, however, cod was the slimy creature on which our ascendancy from a pugnacious maritime nation was built.

Herring were called ‘silver darlings’, no doubt because herring are as lovable as fish get with their large, doleful eyes and pouty lips. But also because in their glittering millions herring were worth a fortune. If Amsterdam was built on the bones of herring, then so too was much of our now beleaguered east coast. Fishing-port towns from the Orkneys and Shetland south to East Anglia, have all prospered or fallen on hard times in tune with the fate of this diminutive fish.

In the Middle Ages the eel also had a currency status reflected in its common name: we called eels ‘fish-silver’. They were a slippery, medieval bit-coin and the wealth eels gave us built cathedrals. Nowadays, the juvenile eel is still a virtual currency, but an illegal one. The black-market trade serving billions of young European eels to the dining rooms of the Far East may undo the species altogether. Meanwhile the eel continues to be just about the most mysterious fish there is. No-one has seen eels spawn, or hatch in the wild and vast tracts of their life-cycles are still subject to speculation. This otherwise marvellous mystery has a downside: eel numbers appear to be crashing and no one really knows why.

The salmon is the sacred fish of Celtic myth for a reason: the huge journeys it undertakes, its athleticism and beauty are awe-inspiring. Along our south coast, which was never covered by glaciers, salmon are amongst our oldest, native vertebrates. They have been British for millions of years. But as the North Atlantic gets warmer, and our rivers fill with agricultural run-off, this fish that has dignified our rivers since long before humans lived here is slowly, inexorably disappearing from the British Isles. The time-scales involved might span many human lifetimes, but the pace of change is accelerating alarmingly.

The immigrant outlier in this cast of endangered but culturally important fish is the corpulent creature that the 17^th century pastoralist writer Sir Isaac Walton described as the Queen of our rivers. There were no carp in British waters before the late fifteenth century, but browse the bottom shelf of WH Smiths and you’ll find twice as many magazines dedicated to angling for this arriviste, or to keeping it in ornamental ponds, as to any other fish, salmon included. The carp was brought over in the Middle Ages as a miracle food-fish and something of a novelty for listless aristocrats. Many to most of the ancient ponds in the English landscape have the keeping of carp in their origins. Centuries later steam-powered trawling and the railways which ushered unprecedented volumes of cod to inland Britain might have tipped carp off a menu they were only just clinging to anyway, but then carp found a new place in the hearts of obsessive British anglers and a whole new chapter began. Carp are a big part of British history, but beyond that carp also tell a more important story of what we have done to our landscape, rivers and seas. They are the one fish in this history not in any danger at all: carp will be all we are left with if we don’t look after the fish that belong here.