Forty sturgeons swim below the Ebro. It had been more than half a century since the ancestral species had become extinct in the river. The predators and especially the obstacles of the weirs and dams that were built were a barrier and a brake on the reproduction of these migratory fish.
The new specimens have come from France and have spent about twenty days acclimatizing at the IRTA aquaculture center in La Ràpita (Montsià).
The release took place on the river beach of Tivenys (Baix Ebre) to great expectations. After growing on the deltaic coast, they will return upriver in fifteen years to reproduce. "It is a historic day for the Terres de l'Ebre, for the river and for the MigratoEbre project," remarked the director of IDECE, Norma Pujol.
After ten in the morning, the 44 specimens of European sturgeon arrived at the Tivenys river beach, inside a container. They were transferred on December 1 to Rápita from the experimental center of the INRAE (National Institute of Research in Sciences and Technologies for the Environment and Agriculture) of Saint Seurin-sur-Isle (New Aquitaine, France).
They are a year and a half old and measure just over twenty centimeters. In recent days they have been acclimatized at the IRTA center, and ultrasound chips have been placed in them for monitoring, which is also facilitated by the sensors that are installed in the Ebro River. Since the middle of the 20th century, there have been no sturgeons left in the river. Ebro.
Inside buckets of water, technicians from different Life MigratEbre collaborating entities have been releasing them in small groups into the river, where they have immediately gone downstream.
As detailed by the scientific coordinator of the project, Marc Ordeix, "if they survive the harsh life of the river", these fish can reach a length of about two meters, weigh a hundred kilos and live a hundred years or more. "They have a life similar to that of the human species. They do not reproduce until they are 15 or 16 years old," said the scientist.
The forecast is that they will stay for a few years, two or three, in the lower section of the Ebro, between Tortosa and Deltebre. Afterwards they will make some intrusion into the sea where they will stay to live for a decade, always within the continental shelf, fifty or one hundred meters from the coast. When the reproductive stage begins, they will return from the sea to the river.
The technicians predict that they will find enough food to survive in the Ebro, which will allow hundreds of pairs to reproduce, both in the area of the Xerta-Tivenys weir and upstream, thanks to the ramp that IDECE has also begun to build. build.
The culmination of MigratoEbre will come with the construction of the fish ramp that began to be built two weeks ago on the Xerta-Tivenys weir.
In this way, the ecological connectivity of the river will be "guaranteed" to facilitate the reproduction of migratory species such as the sturgeon, but also the stingray and others.
As Ordeix has pointed out, now the Ebro River has "a good physical-chemical and biological quality, but when the migratory fish reach the weir, "they are all overcrowded" and predators of all kinds, fishermen and invasive species, such as the catfish and cormorants, "they eat them." "They have to be able to go higher, to spread out and have more reproductive success," said the coordinator of MigratoEbre. "We will increase the reproduction areas up to 10 or 20 times," he assured.
The director of IDECE has recognized that the works will be conditioned by the weather conditions and those of the river -if the flows are higher than expected-. The ramp will be about 70 or 80 centimeters deep so that the sturgeons "are not afraid" to pass through it, and will have elements to reduce the force of the water current. With it, migratory fish will be able to climb the more than three meters of the weir and go look for new spaces as far as Flix - one was also made in the Ascó weir -. The works will cost close to one million euros.
