the zebra musselconsidered one of the most dangerous invasive alien species due to its economic impact and its damage to ecosystems, is already present in eight of the fifteen river basin districts in Spain, after adult specimens have been found in the Segura basinwhere it could have reached, according to experts, from the Tagus through the transfer.
The Segura Hydrographic Confederation reported on Monday its appearance in the Talave reservoir (Albacete)which will be emptied to a certain level (the zebra mussel lives about 2-5 meters deep) to cause the death of the specimens present by desiccation and thus prevent its spread.
According to data from the Ministry for Ecological Transition, the zebra mussel is also already present in the demarcations of the Guadalquivir, the Andalusian Mediterranean basins; Guadalete and Barbate; the Tinto, Odiel and Piedras; the Júcar, the Ebro and the river basin district of Catalonia.
For now, the Miño-Sil, Galicia Coast, Eastern Cantabrian, Western Cantabrian, Duero, Tagus, Guadiana are saved from the presence of this species.
According to the head of the Technical Service of the Júcar Hydrographic Confederation and an expert on this invader, Concha Durán, it is logical that the zebra mussel settles in “calcareous” Spain, because to form its shell it needs calcium carbonate. On the other hand, “silicia” Spain is resisting for now against this invasion.
The zebra mussel is in the ‘top ten’ of the most dangerous invasive alien species on the planet due to its great socioeconomic and ecosystem impacts (for human health it does not represent a danger), and its arrival anywhere is always “bad news”, lamented Durán.
“You have to be drastic at the beginning”
The Segura demarcation was one of the few that was still not affected, probably by the control exercised over the boats and the monitoring of the species, according to Durán, who stressed that, once detected, it is necessary to be “drastic”.
In his opinion, in addition to emptying it, it would be necessary to stop the use of the reservoir (fishing and navigation) and carry out an exhaustive study to see how far the population of this mussel has come.
“After many years of experience, my advice is that you have to be very drastic at the beginning, that’s when you can do something. Then you can only learn to live with the problem “, she added.
This species is grouped in “very large” clusters forming balls that can block any water intake, causing considerable damage to hydroelectric plants, irrigators, town halls, etc. From an ecological point of view, its impact is “brutal”, since when it lands on any solid surface, it displaces other organisms, including other shell-bearing species whose survival is threatened. In addition, being a “very powerful” filter feeder, it consumes a lot of phytoplankton and can change an entire ecosystem.
After confirming the settlement of a population, it is most likely that it will disperse at high speed in nearby basins and with similar characteristics, according to Francisco Oliva, professor at the University of Murcia and coordinator of the Life Invasaqua project, to combat exotic aquatic species.
Given its high reproductive capacity (a specimen can release more than 1 million larvae a year) and the absence of specific predators, it is expected that it will quickly colonize the affected reservoirs, added Oliva, who has warned that in a basin like the del Segura, the socioeconomic impact can be disastrous for agriculture.
Some confederations have already spent more than 30 million euros on the direct management of the species and a study in the Hydrographic Confederation of the Ebro, puts the indirect losses caused by the zebra mussel at more than 1,600 million, he explained.
In his opinion, to the reduction of the level of the reservoir and the exhaustive sampling to determine the true scope of the population, it would be necessary to add the temporary prohibition of activities that could lead to the expansion of larvae to other reservoirs or aquatic systems, such as navigation or sport fishing.
The transfer, possible culprit?
“It is very likely that this species has colonized the Segura basin through the Tajo-Segura transfer. For years, scientists and technicians have warned of the need to filter the flow that constantly reaches the Talave reservoir from areas infected by zebra mussels in the Júcar river basin”, he lamented.
The zebra mussel appeared for the first time in Spain in 2001, specifically in the Ebro and Júcar basins. It is a kind that endangers biodiversity native, but also the hydraulic infrastructures. The basin organization has warned that the main vectors of spread are boats, which is why it has limited navigation in the dam and is carrying out an information campaign about the protocol that must be followed to prevent the spread of the plague.
The basin organization periodically takes planktonic samples in order to detect larvas of this invasive species. The controls also include the review of adult specimens and the inspection of the surroundings of the suspected points of spread.
the zebra mussel They come from the Black, Caspian and Azov seas. According to information published by the Júcar Hydrographic Confederation, the International Union for Conservation of Nature considers it one of the 100 most dangerous invasive alien species in the world, and it is also included in the National Catalog of Invasive Alien Species.
The adult shell has an elongated triangular shape and can measure up to four centimeters in length. The valves have alternating light and dark bands in a zigzag pattern that can vary both in shape and color. It is not edible.
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