Heat wave combats Mediterranean mussel harvest in Spain



“There’s nothing left here,” Javier Franch sighs, shaking the heavy rope of mussels he’s just pulled to the surface in northeastern Spain. They all died.

With the country facing a long, brutal heatwave this summer, the water temperature in the Ebro Delta, the main mussel producing region of the Spanish Mediterranean, has reached 30°C (86°F).

And any farmer who did not remove the slugs in time will have lost everything.

But that’s not the worst of it: most of next year’s crop also died in one of the most severe marine heat waves in the Spanish Mediterranean.

By the end of July, experts said the western Mediterranean was experiencing an “exceptional” marine heatwave, with temperatures continuing to rise above normal, posing a threat to the entire marine ecosystem.

“The high temperatures have shortened the season,” says Franch, 46, who spent nearly three decades working at the company his father founded, which has seen production drop by a quarter this year.

The harsh sun has heated up the mix of fresh and salt water along the delicate coastal wetlands of Catalonia as the Ebro River flows into the Mediterranean.

On a hot summer morning in Deltebre, a Delta municipality, mussel rafts—long wooden structures attached to ropes that can each weigh up to 20 kilograms (44 pounds) of mussels—must be bustling with workers who move quickly during a busy season.

But there is hardly any movement.

“We lost the residual yield, which wasn’t much, because we were working forward so we wouldn’t go through this,” explains Carles Fernandez, who works as a consultant for the Federation of Mollusc Producers (Fepromodel) in the Ebro Delta.

“But the problem is that we’re missing out on the small stock for next year and we’re going to have a big cost overrun.”

Millions of losses

Initial estimates are that the heat wiped out 150 tons of commercial mussels and 1,000 tons of young stock in the delta.

Producers are counting their losses at more than one million euros ($1 million) given that they will now have to buy the tiny mollusks from Italy or Greece for next year.

“When you have a week when temperatures are above 28°C, there can be some deaths, but this summer it lasted for about a month and a half,” says Gerardo Bonet, president of Fepromodel, “with temperatures reaching almost 31°C.

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Typically, the two bays of the Ebro delta produce about 3,500 tons of mussels, and 800 tons of oysters, making Catalonia Spain the second largest producer in Spain, although it is still far from the production of Galicia, the northwestern region on the cold Atlantic coast.

For years now, the harvest season has been brought forward in the delta, shortening the season that ran from April to August.

mediterranean “tropical”

Vulnerable to coastal erosion and a lack of sediment supply, the rich ecosystem of the Ebro Delta – a biosphere reserve and one of the most important wetlands in the western Mediterranean – is particularly vulnerable to climate change.

And this harsh summer, when Spain suffered 42 heatwave days — a record three times the average over the past decade, says the AEMET national forecaster — also left its mark underwater.

“Some marine populations that are unable to handle such high temperatures over a long period of time will suffer what we call mass deaths,” says marine biologist Emma Cebrian of Spain’s National Research Council (CISC).

“Imagine a forest, like 60 or 80 percent of the trees die, with the resulting impact on the associated biodiversity,” she says.

A succession of heat waves on land has led to another sea wave that – pending analysis of all the data in November – may turn out to be the “worst” in this region of the Mediterranean since records began in the 1980s.

Although marine heat waves are not a new phenomenon, they are becoming more extreme with increasingly dire consequences.

“If we compare it to a wildfire, one could have an impact, but if it keeps happening, it probably means that the affected population is not able to recover,” Cibrian said.

Experts say the Mediterranean is becoming “tropical,” and mollusk farmer Franch is shocked by mounting evidence as his boat glides between empty mussel rafts in a bay without the wind breathing.

He is considering increasing his production of oysters, which are more resistant to higher temperatures, but currently only account for 10 percent of his production.

But he hopes this will help secure his future in a sector that directly or indirectly employs 800 people in the Ebro Delta.

“(The sector) is under threat because climate change is a reality and what we are seeing now will happen again,” he says worriedly.

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