Red swamp crayfish: 50 years since the Guadalquivir disaster

How the red swamp crayfish conquered the Guadalquivir

In the spring of 1974, the aristocrat Andrés Bores Saavedra legally imported two tonnes of Procambarus clarkii and released them into the Guadalquivir marshes. The decision, made privately on an estate, would reshape the ecological map of Doñana for the next five decades.

The red swamp crayfish found no natural predators. Today it is in every stream in Andalusia, and wherever it appears, the common frog and much of the wildlife that once dominated the wetlands disappear. Meanwhile, the marsh has reached a point of no return: analyses point to an irreversible transformation that cannot be undone with current tools.

The "Iberian" crayfish wasn't so Iberian either

The debate over what is native has its complications. The archives of the Doñana Biological Station document that Philip II already ordered crayfish to be brought from Tuscany in the 16th century to restock the Tagus. In other words, the crayfish we have called Spanish for centuries may have been an introduction by well-meaning officials. The precedent invites a broader perspective on the current crusade against the American invader: 500 years ago we did the same with the Italian one.

The business that looks to Sweden

While it is considered a nuisance here, in Isla Mayor it is fished, seasoned and shipped to Sweden, where it is a delicacy consumed with devotion. The commercial paradox is complete: the crayfish that destroys the local ecosystem feeds an export market that pays well. That said, it is hardly sold alive; the journey requires boiling it, and that has hindered its acceptance in Spanish cuisine.

Some voices point out that blaming a single aristocrat falls short: in other basins, such as the Tera or the Jiloca, it was environmental organisations of the time that promoted restocking with foreign species under the banner of good intentions. The road to hell, the classic saying goes, is paved with them.

Fifty years on, the crayfish keeps gaining ground. The lesson comes at a price: a single individual's gesture can rewrite the natural history of an entire country. And proof of the trinc is that today, to undo it, no budget is enough.