This article was featured in Eurofish Magazine 6 2025.
Mussels, oysters, and clams are produced in the Ebro delta for distribution to Barcelona and the rest of Spain.
The river Ebro travels in a south easterly direction from its origin in the Cantabrian mountains in northern Spain to the Mediterranean coast between Barcelona and Valencia. The Ebro delta in the province of Tarragona in the autonomous community of Catalonia is an area of some 320 sq. km, a quarter of which comprises a nature reserve. The reserve hosts a shellfish industry producing mussels, oysters, and clams in the bays, Fangar in the north and Alfacs in the south. Production is managed by the federation Fepromodel (Federació de Productors de Mol·luscos del Delta de l’Ebre), a body with 56 concessionaires, which also carries out research and testing of the shellfish to guarantee quality and food safety.
Four fifths of Mediterranean mussel production in the Ebro delta area
Gerardo Benet, the manager of Fepromodel, says the federation produces about 2,700 tonnes of Mediterranean mussels in the Alfacs bay and a further 800 tonnes in the Fangar bay, while Pacific oyster production is 500-600 tonnes in Fangar and around 100 tonnes in Alfacs. Mussel spat is collected on ropes in the two bays during the season from December to March or April but is also supplemented with imports from Italy or Greece, if spat collection is poor. Once the spat has settled on the ropes suspended in the Alfacs bay, they are moved to Fangar where the winds are stronger and water circulation in the bay is better. The ropes are suspended from wooden frames, and the mussels grow until they are harvested the following spring. Mussels thrive in water temperatures from 15-24 degrees C. At 26 degrees the mussels stop feeding and at 28 degrees, if there is prolonged exposure, the animals will perish. Oysters, however, are more resistant to high temperatures, and thus offer an insurance policy if mussel mortality is high.
One of the federation’s main functions is to get rid of the waste, mainly discarded shells, byssus threads, and residual meat, which is produced by the producers. Dead bivalves, or those that are too small to be marketable, amount to 1,000 tonnes each year. The federation is also responsible for the sale of mussels. The best quality product has 40-60 mussels per kilo with a meat ratio of 100 to 250 g per kilo. The bays are classified as a B zone so the mussels must be depurated before they can be released on the market. There 12 depuration centres in the delta, Mr Benet states, so depuration is not an issue. On the Spanish Mediterranean coast 70-80% of the mussels are produced in the Ebro delta most of which is sold at the wholesale market in Barcelona while the rest goes to other parts of Spain. Apart from wholesalers, buyers are retail chains, fishmongers, and restaurants. The product is sold live in wooden boxes or nets of assorted sizes depending on the buyers’ preferences.
Blue crab is less of a threat today
Mr Benet has considered adding value to the mussels either by canning or freezing but it calls for a significant investment which may not be justified by the volume of production. Another activity the producers participate in is tourism. Boats with tourists sail to the installations where they can see how mussels and oysters are grown. The industry is of economic importance in La Rapita and the surrounding area. Apart from tourism, the number of jobs in management and maintenance of the installations, depuration centres, and in transport and logistics amount to more than 700 people, Mr Benet calculates. But many of these positions are not full-time and the workers must find other job opportunities as well. Some producers, for example, grow both mussels and oysters which corresponds to full-time work. The industry also faces threats, the biggest of which is probably the impact of climate change. The average depth of Fangar bay is about 2 m with a maximum depth of 4 m, while Alfacs bay is about 4 m on average and 6.5 m at its deepest. The shallow water results in high water temperatures that can affect production, as well as negatively influence spat production or nutrition for the bivalves. Another issue is predation from species such as salema (Sarpa -salpa), and blue crab (Callinectes sapidus). To protect the stocks producers drape them with nets. This is not the ideal solution as it affects the water flow and the currents, but the alternative is worse. Blue crabs were first detected in 2012 and two years later the population exploded with major consequences for the shellfish producers. Since then, we have learnt to manage this predator, Mr Benet explains, and now there is a market for it so fishers catch and sell it at the auction where they can get a decent price. This has put pressure on the resource and reduced the impact on the shellfish. As shellfish farmers Fepromodel members are not allowed to fish for blue crab, as this is decreed to be the exclusive prerogative of commercial fishers.
An illustrated map of the area
Increasing production carries rewards but also risks
Production on the whole has been largely stable for the last 40 years though climate impacts in the last few years have caused a slight decline in output. Mr Benet says the federation could produce more—perhaps even up to three times the current volume, but the drawback would be apparent at harvest time. Producing such a large quantity elevates the risk of losses as there is only a narrow window, which has been getting narrower over the years, for harvesting before the water temperature increases to critical levels. Moreover, lower production volumes lead to higher quality as the available nutrition per line increases and handling and logistics is easier. The volume produced also influences the unit price which this year was about EUR2.7/kg. If a large volume were produced and unloaded onto the market it is likely to reduce the unit price. For Fepromodel the benefits and drawbacks of increasing production need to be carefully weighed.
