A new stage of aquaculture development has begun in the Ebro Delta, one of Spain’s main centers for shellfish farming. For many years, local oyster and mussel producers were forced to import seeds of the Pacific oyster (Crassostrea gigas) from abroad, primarily from France. This dependency not only increased costs but also created additional health risks for marine organisms.
The situation changed thanks to an initiative by the Institute of Agrifood Research and Technology (IRTA), which, with the support of the Catalan government, launched a project to produce oyster seeds directly in the region. In July last year, 145,000 seeds entirely sourced in Catalonia were planted for the first time at experimental sites in Sant Carles de la Ràpita (Tarragona).
Local production allows for control over the quality and sanitary conditions of shellfish at every stage. To obtain seeds, adult specimens best adapted to the Ebro Delta’s conditions are selected. In IRTA laboratories, they are stimulated to spawn, and the resulting larvae grow for several weeks in a protected environment. Once they reach the required size, they are moved into special nylon structures—so-called ‘lanterns’—and then onto suspended ropes, where the oysters continue developing until they reach market size.
This approach not only gives the region independence from external suppliers but also helps adapt to a changing climate. In recent years, mussels, which have traditionally dominated the Ebro Delta, have increasingly suffered from heat: when water temperatures rise above 27 degrees, their growth slows and harvesting has to be done earlier than usual, reducing production volumes. In contrast, the Pacific oyster copes better with high temperatures and continues to grow even in summer, when mussels experience stress. This opens up new opportunities for business diversification and sustainable sector development.
Alongside Catalonia, interest in the Pacific oyster is also growing in other regions of Spain. In Galicia, for example, this shellfish species is actively spreading naturally. In the northern rías (Rías Altas) oyster populations have already become established, while in the southern rías (Rías Baixas) they are just beginning to form. Scientists from the Institute of Marine Research (IIM-CSIC, Vigo) are studying the dynamics of this process to understand how the oyster settles into new areas and how this affects the ecosystem.
Modern technologies are used for monitoring: drones and artificial intelligence allow for precise mapping of the seabed and tracking population growth in real time. This is important because oyster larvae can remain suspended in the water column for up to a month before settling on the bottom. The spread of the reef oyster can affect local species and biodiversity, but with proper management, it can create new habitats and improve water quality through filtration.
In Galicia, the reef oyster is not considered an invasive species, so its cultivation and harvesting are permitted. However, scientists emphasize the need to carefully monitor the balance to avoid displacing local species.
Projects in the Ebro Delta and Galicia reflect a broader trend in Spanish aquaculture: the sector is seeking ways to achieve sustainability, reduce dependence on imports, and adapt to climate change. Local oyster seed has already shown good results in terms of productivity and resilience, and experts hope this experience will serve as an example for other regions of the country.
Thus, Spain is relying on its own resources and scientific advancements to maintain its leadership in seafood production and ensure food security amid global challenges.
