Environment minister, Cristina Narbona, insisted strongly today that the government "has not thrown in the towel" in the fight against the zebra mussel "no matter how diffficult it may be," adding that, if required, "state security forces and even the army" will be deployed to deal with the threat.

"The government has not washed its hands of this problem," continued Ms Narbona at a press conference in Zaragoza, where regional Environment ministers from the nine autonomies supplied by Ebro valley reservoirs (Cantabria, the Basque country, Navarra, La Rioja, Castilla León, Castilla La Mancha, Aragón, Cataluña and Valencia) -are gathered to discuss possible measures.

Exerts warn that the plague will spread extremely rapidly as an adult female may produce between 30,000 to 1,000,000 eggs per year with spawning taking place in the months from late spring to early summer.

In 1850 zebra mussels were first detected in Holland, and quickly spread across Europe along the canal system. They were first detected in the Great Lakes in 1986 since when they have spread to a large number of waterways, including the Mississippi, Hudson, St. Lawrence, Ohio, Cumberland, Missouri, Tennessee and Arkansas.

The invasive and highly aggressive species disrupts ecosystems, killing local unioid mussels (by starvation as they are better able to compete for food), while also damaging harbours, boats and power plants. In the USA, water treatment plants initially incurred huge losses as the microscopic larvae infiltrated directly through water intake systems.

It is estimated that the problem has caused billions of dollars of damage in the USA, and no effective solution has yet been found.