Climate change and human restraint appear to be behind the spectacular catches drawing anglers to the far north islands

Forty years ago, the wife of the editor at the local paper for the remote Lofoten islands in Norway’s far north had an idea to boost its tiny circulation. The newspaper started to award a bag of coffee and a certificate to any angler who landed a cod over 30kg (66lb).

Now the paper’s records, painstakingly compiled over the decades, bear witness to a remarkable outcome of climate change and far-sighted fisheries management.

The catch of monster cod has exploded in the last five years, as the fish have feasted on shoals of capelin thriving in warmer waters. Meanwhile, commercial fishing has been tightly controlled, allowing the fish to age and grow … and grow and grow.

Facebook Twitter Pinterest Traditional red fisherman’s cottages in the Lofoten islands. Photograph: Alamy

Anglers are catching unheard of numbers of kaffetorsk, or “coffee cod”, and the Lofoten Post has had to give away almost half a tonne of coffee this year. As of last weekend, 490 giants had been reported, up from 289 last year and just 49 in 2010. The biggest was 45kg (99lb).

Managing cod stocks is not rocket science – it is much more complicated than that Knut Korsbrekke

“Commercial fishing and angling are extremely important for Lofoten, and the kaffetorsk have become a concept, almost a brand,” says Kai Nikolaisen, the paper’s official coffee-cod correspondent. “I walk through the harbour and fishermen say look, that’s the kaffetorsk guy. When I started the job in 2006, we had only a dozen such fish every year.”

Commercial fishermen support the Lofoten Post’s less than scientific observations.

“We’ve seen a lot of big cod this season, that’s a fact – this year seems to have been extraordinary,” says Jan-Erik Indrestrand for the Norwegian Fishermen’s Association, the professional fishing union.

Anglers have come from abroad to enjoy the bonanza. Last month British pensioner Bert Williams reeled in a 42kg (93lb) animal, the largest ever caught by a Briton, further north up the coast at Sørøya. Two weeks earlier a Swede, Marica Eriksson, broke the world record for a fish landed by a woman, at 38kg (84lb).

The phenomenon of massive cod is partly due to the warming climate, which has greatly expanded the area where the cod can feed, says Knut Korsbrekke, a specialist at the Institute of Marine Research in Bergen. But Norway also began to place limits on the commercial harvest in the 1980s, and this is bearing fruit, he says. In 1989, after an “extreme cooling event” in the Barents Sea when stocks declined rapidly, Norway and Russia agreed to close down the fishery altogether.

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“Try doing that in the EU,” says Korsbrekke, who compares the “huge success” of Arctic fisheries management with the North Sea, where overfishing has meant cod populations are still only a quarter the size they were in the 1970s. North Sea cod stocks are a “terrible mess”, he says, as countries haggle over quotas. In contrast, Norway and Russia have a long history of successful cooperation.

“Managing cod stocks is not rocket science – it is much more complicated than that,” Korsbrekke says.

Each female lays some 8m eggs, 1.3mm across; at peak spawning in early spring, the density of eggs can be as high as 28,000 per square metre. Were all the Barents Sea spawn to be placed side by side, an egg at a time, they would stretch for more than 1bn km, Korsbrekke has calculated.

But only two eggs per female survive to become mature fish. It takes between 10 and 15 years for them to grow to 30kg, and perhaps as long as 20 – fish can be aged by counting the growth rings in an ear bone, like a tree. And while some cod can live 30 years, the potential for them to grow so large depends on availability of food, and modest harvesting rates.

Favourable conditions due to climate change have happened before – the 1930s saw a similar warm period when cod stocks took off, and huge fleets of trawlers landed hundreds of thousands of tonnes before the war. But it is not easy to predict whether the current trend towards an abundance of Barents Sea cod will continue, Indrestrand says. Russia is reporting “vast amounts” of small cod at great depths in the east, possibly related to falling temperatures.

“It is normal that the bigger fish arrives first, while in the later part of the season we see a more mixed population with a lot more of the smaller, more normal, fish,” Indrestrand says. “So the big cod may not reflect the real situation in the stock.”

Commercial fishermen used to be at loggerheads with scientists demanding stock control, says Korsbrekke. “But we have established a level of trust – we are working for the fisherman too, to create a healthy ecosystem that can be harvested sustainably. As soon as they realise that our objectives coincide, they cooperate.”

Norwegian anglers have had their share of luck, with the warming climate roughly doubling the area where the cod can thrive and reach such staggering size. But they are also reaping the rewards of human intervention, Korsbrekke says.

“It pays to utilise the resource in a rational way.”