Galician shellfish workers are restless. Rita Míguez has been planting and collecting delicacies in the Vigo estuary for 16 years and her opinion is clear: “The sea stops producing. They reserve an area for a year without working and if you go expecting to find commercial size mussels there is nothing. We’re very worried about our future.” 200 kilometers away, in the wild Rías Altas, “the descent is tremendous,” agrees Cristina Fernández, spokeswoman for the shellfish workers of Cariño (A Coruña). In the laboratories of the University of Vigo they found at least part of the answer and it has to do with the meteorological phenomena of climate change.
Míguez, president of the Arcade (Soutomaior-Pontevedra) mussel fishermen’s association, explains that every year she and her colleagues invest their money and effort in planting certain areas, but the mussels stop growing or die straight away: “Years ago, the 80% , today it does not reach half”. The problems began to be noticed eight years ago with the fine clam. They stopped taking her to allow her to recover, but they couldn’t, “everything dies” with no remedy. Now the same is happening with the theoretically hardiest strain, the Japonica. And the cockle, decimated by a parasite for a decade, doesn’t lift its head either. Of Cariño, Fernández says they stopped extracting clams in March 2021 because there weren’t any more. And with the longueirón, another species dug out of the sand, they are on the same path.
Pollution, invasive species and climate change are some of the factors believed to be causing this decline in the shellfish sector. The shellfish workers are demanding action. “The Xunta, the brotherhoods and the universities must come together. Scientists need to figure out why, and if something needs to change, we change it. The shellfish women spoil our environment because it feeds us. We’ll do what the technicians tell us,” says Míguez. The spokeswoman for the shellfish collectors of A Illa de Arousa, Carmen Dios Castro, from the richest estuary in Galicia, believes that “there is still “time to do something before it gets worse”: “We shellfish collectors do our job because it is our survival, but there are problems that we don’t know what causes them or how to deal with them; we don’t have a university degree, but we know exactly what’s happening, even if we don’t know how to scientifically call it.”
Elsa Vázquez Otero, professor of zoology at the University of Vigo’s Faculty of Marine Sciences, has some of the answers to the questions raised by shell collectors who have spent years studying some of the factors that may explain these changes. Since 2014, his team has been studying the effects that the low salinity of the sea and the warming of the sand are having on the mussels, which are causing the increasingly frequent consequences of torrential rains and heat waves in Galicia. These researchers reproduce in the laboratory real conditions that have already occurred on the Galician coast and then observe what happens to two of the most sought-after species on the markets: mussels (both the fine ones, the snail and the japonica) and the cockles.
A clam fisherman in the area of Vilanova de Arousa.ÓSCAR CORRAL
The unusual torrential rains that have hit Galicia in recent years have abruptly and for days reduced the salinity of the sea by up to 60%. When normal parameters in estuaries are around 30 grams of salt per liter of water (slightly less in winter), Vázquez and his team have obtained readings of between 5 and 10 grams per liter after extreme downpours. The zoologist explains that in such hostile conditions, mussels and cockles huddle together to protect themselves, waiting for the tide to rise and salinity to rise. But as the situation continues, they eventually have no choice but to open their shells, and the “shock” with such a small salty sea “settles their physiology out of control.” “If it stays like this for several days, the mussel can’t take it anymore, it can’t defend itself and it dies,” he warns. If, at best, it survives, Vázquez adds, its vital functions will be altered and its growth and reproduction will decline.
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The same thing happens at extreme temperatures. In heat waves like this summer, low tide is a furnace for mussels. Vázquez explains that clams and cockles bury themselves in the sand as much as possible in search of freshness, but they can only do so up to the tip: the length of the tubes called siphons through which they breathe and which reach the surface have to reach. The effects of this stressful situation are repeated: death and decline in growth and reproduction. “In June we simulated a four-day heat wave and we just had a six-day heat wave,” says the scientist.
In the Arousa Estuary, brotherhoods of fishermen and conservationists, united in a platform that has for years denounced the degradation of the area, are focusing on official Xunta data. According to these records, mussel production has declined by less than half since 2000 and cockle production has declined since 2008, reaching just 23% of last season’s harvest. A Illa de Arousa shellfish workers agree that the change in the number and size of mussels is “a palpable reality across the estuary,” which has worsened even over the past two years. “For years we have observed the gradual decline of the cockle, which has been an economic mainstay for the sector, and a slowdown in the growth of the mussel, but the last two years have been fateful and we are facing a drop in production,” laments Carmen Dios. .
In this estuary, 75% of the mussel production is already achieved through the provision of seed, since otherwise there would be practically no specimens for sale. “When I was a girl, on the beach to build a handful of sand for a castle, you had to separate the shellfish, but today that excess is part of the past and we’re stuck in a vicious circle that hasn’t been resolved. And the proliferation of algae through the use of fertilizers also deprives the species of oxygen,” explains Dios, who has been a mussel fisherman since she was 14 and is now 46.
The Consellería do Mar de la Xunta recognizes the impact of climate change on shellfish production, but also points to other factors such as pathologies, predators or exceptional situations such as the pandemic. In his opinion, the fluctuations that the quantities of shellfish show, both upwards and downwards, show that the impact on production varies between zones. Last year more than 7,000 tons of mussels were sold in the Galician markets, a figure slightly below the 8,000 average sold since 2014. The bad situation of some estuaries is compensated by the better situation of others.
Faced with the scientific studies that the sector constantly demands, Mar defends the “constant monitoring” of the state of the mussel beds that is being carried out and the “intensive” work that is being carried out in collaboration with the fishermen’s associations where the production. “We understand that the effects of climate change should be generalized, but analysis of the data shows that there are areas that are in a worse situation, regardless of their geographical location, such as the Arousa and Ferrol estuaries, where work is being done carried out intensively in order to increase their productivity, while others are achieving good results, such as the mouths of Muros, Noia and Pontevedra,” the Ministry points out.