Bermeo sits in Bizkaia, in the Basque Country, and Santoña sits sixty-some miles west in Cantabria, a completely different region with its own government, its own dialect of Spanish, its own idea of itself. What they do share is one uninterrupted stretch of the Cantabrian Sea. A morning's drive apart at most, this one run of coast produces two of the most sought after tins in the world: an anchovy cured for the better part of a year, and a tuna caught the slow way, one hook at a time, in a summer campaign that hands its catch to a tin within months. Neither industry looks anything like the other, and both come out of the same water and for the same reason.

Start with Bermeo, the town was founded in 1236 around a natural harbour, and within two centuries its boats were already going after something almost nobody else on the coast would touch: the North Atlantic right whale, migrating close enough to shore to be hunted from open boats with hand harpoons. By the seventeenth and eighteenth centuries, Bermeo's whaling had become the town's golden age, its ships ranging as far as Newfoundland to keep the trade running once the local whales thinned out. The coat of arms still shows a ship in pursuit of a whale. Bermeo remains the most important fishing port in the whole Basque Country today, the boats no longer chase whales, but the willingness to go further than the fish require is the same one that built the town.

That willingness was never only Bermeo's. In 1534, records show fifteen ships from Gipuzkoa working the Irish fishery, a fifth of the entire fleet. Standing alongside them were Biscayan vessels out of Ondarroa, Lekeitio and Bermeo doing the same. This is the detail worth knowing: fishermen from three small towns on one short coast were working two different foreign coastlines for cod and whale before Spain had canned a single fish. Ondarroa, the largest of the three today, still carries the instinct forward in the fish it built its name on. Last year the Basque fleet, most of it working out of Ondarroa, landed 7,100 tonnes of bonito del norte by early August alone, sixty percent of the entire Spanish catch, every one of them still taken the old way, one baited hook at a time, in the summer campaign the coast calls the costera del bonito. The scale has changed. The method to get there did not.

Sixty miles along the coast in the other direction, in a different region entirely, Santoña does not chase anything. It simply waits. More than forty canneries work inside one small Cantabrian town, nearly all of them turning the same modest fish, the Bay of Biscay anchovy, into the tin regarded as the finest version of it anywhere. What happens to that anchovy after the boat brings it in takes the better part of a year: buried in salt, left to break itself down and rebuild into something else entirely, filleted only once it is ready, never before. Santoña never went further out to sea than anyone else. It just refused to rush what came back.

Put the two towns side by side and the map stops looking like an accident. Ondarroa's bonito is caught at the edge of what a rod and line can reach, in a campaign that lasts weeks and produces a tin within the year. Santoña's anchovy is caught close to shore, in a season that lasts days, and spends most of a year becoming what it is before it ever sees a tin at all. One town solved the problem of distance, the other solved the problem of time. Between them, on one stretch of coast that never agreed on a language or a government, they quietly decided what two completely different kinds of patience taste like.

That is the thing worth carrying out of a shop the next time a Basque bonito and a Cantabrian anchovy sit on the same shelf. Neither tin got there by accident, and neither got there quickly. One coast simply found two different ways to refuse the easy version.

A fish that lives a kilometre down, canned in a town built on eel.

In 1942 the fritadeiras da Murtosa, the eel-frying women who worked the shallow Ria de Aveiro lagoon, had grown their trade past what a kitchen could hold and joined with a handful of businessmen from neighbouring Estarreja to build a proper cannery. Eel, fried and packed in escabeche, was the reason the house existed at all. So central to Murtosa's economy that during the Second World War its preserved eel became one of the town's first real export contracts, feeding Mussolini's troops. Eighty-some years on, Comur makes more than thirty different tins, and while sardines now sell in the greater numbers, eel is still the thing the house is known for.

This week's tin is neither. It is peixe-espada, the black scabbardfish, and it comes from nowhere near the lagoon that built the company. Off Madeira, roughly a thousand kilometres south of Murtosa, fishermen out of Camara de Lobos still set longlines eight hundred to thirteen hundred metres down, baited with squid, to reach a fish that never comes up any shallower. What they haul up looks almost nothing like a fish at all: a long black ribbon of an animal that the island turned into one of its defining dishes, fried in strips and served, famously, with banana.

Comur steams it instead, and packs the fillets, soft and white under that black skin, in extra virgin olive oil with nothing else but salt. A 120 gram tin holds 80 grams of fish once drained, mild and firm rather than oily. Warm it through and lay it over rice, or, if you want the version Madeira actually eats it, alongside a few slices of banana.

$27.00 at The Fantastic World of the Portuguese Sardine.