Zebra mussel, a dangerous invasive species, is taking over Spanish rivers

The Water Quality Area of ​​the Júcar Hydrographic Confederation (CHJ) confirmed this week that zebra mussel specimens were detected (Dreissena polymorph) inside Alarcon reservoir (Cuenca)in the upstream section of this river under the Shock Plan for the control and monitoring of invasive alien species.

This was announced this Friday by the Ministry of Ecological Transition and Demographic Control in a note reminding that the waters of this reservoir have been continuously monitored since the larvae of this invasive species were discovered in 2018.

The appearance of adult specimens of this mollusk shows: zebra mussels congregate in the Alarcón reservoirThe hydraulic infrastructure with the greatest capacity in the Júcar hydrographic limitation is therefore a discovery that “concerns” managers and users alike, due to the severe ecological and economic damage this exotic invasive species can cause.

In this sense, Concha Durán, Head of Service in the Field of Water Quality, underlined the following: The Alarcón reservoir “has many uses, playing a very important role in the entire exploitation system of Júcar and particularly the Tajo-Segura Transfer.The implications for irrigation and hydraulic infrastructures could be very significant».

Therefore, soon after several adult specimens were detected in the reservoir, the CHJ initiated different prevention measures to try this. prevent the zebra mussel from expanding rapidly downstream of Alarcón.

Browsing limitations

Most importantly about you navigability, According to Durán, who explained that when the presence of this species is detected in a body of water, the rules governing navigation change as they impose a kind of quarantine in the reservoir, “Ships whose owners want to navigate Alarcón will not be able to do so on any other reservoir”it was stress.

The work of CHJ administrators is now focused on analyzing how the colony behaves in the waters of the reservoir and identifying areas most prone to consolidation, given that an adult specimen of this inedible mussel species can reach three centimeters in length. and multiplies massively, forming colonies that cling to any hard substrate so that IThey come to block channels, pipes and doors.

Durán also said that one of the biggest problems when fighting this mollusk is that there is no specialized tool to do it, and although the pressure and speed of the waters are known to have an effect, “the truth is that all treatments available to destroy it also damage the entire ecosystem affected by the water.” gives”.

In this regard, the head of the Service in the Field of Water Quality recalled that the CHJ has recently signed a new service outsourcing contract worth approximately 250,000 euros for monitoring zebra mussels and other invasive species. expansion.

He also highlighted that for the purpose of comprehensive and reliable monitoring of invasive species, the CHJ has this year a very innovative tool, environmental DNA. the remains of the creatures that lived there.

It also reached reservoirs in Albacete and Murcia.

Just a few days ago, the zebra mussel It is also active in the adult populated Talave (Liétor-Albacete) and Camarillas (Hellín-Albacete) reservoirs and is also beginning to be recorded in the Cenajo reservoir (Albacete/Murcia). As approved by the Segura Hydrographic Confederation. As such, it is already present on more than half of Spain’s hydrographic borders; Currently, only those in the northwest of the Peninsula have been saved.

Technicians of the basin service have documented an increase in the density of these larvae. While the density in the Camarillas reservoir was 0.003 units per liter (ud/l) in May, it already showed values ​​up to 0.106 in August.

In Talave, zebra mussel larvae with a density of 0.006 units/l were detected in the July campaign and reached a concentration of 0.008 units/l in August. Finally, the larval density observed in Cenajo during this last sampling reaches 0.005 units/l.

In contrast, studies have revealed the presence of this mollusk in adulthood in the Camarillas and Talave reservoirs, where this invasive species has been detected for spring in the Segura basin.

Sampling to monitor zebra mussels will continue until mid-Octobercorresponds to the reproductive cycle of the species. In addition, CHS is placing information signs at various points in the watershed and increasing control of recreational boating among affected populations.

Since the start of summer, navigation has been prohibited in the Camarillas reservoir due to the presence of adult zebra mussel populations, and a single access point has been defined in the Cenajo reservoir and an obligation to clean up any contact items. waters at an official certified cleaning station.

One of the world’s most harmful invasive species

The zebra mussel (Dreissena polymorpha) is considered one of the most harmful invasive alien species in the world, according to the International Union for Conservation of Nature (IUCN).

Its main effects on the ecosystem and economic resources are due to its high growth capacity, forming colonies and aggregates that even clog pipes or tubes.

Regarding the ecosystem, as a major consumer of phytoplankton, it improves water clarity, changes water conditions and replaces other native species.

It can also almost completely cover the slopes or shores of the water bodies in which it proliferates, negatively affecting tourism and other recreational activities such as sport fishing and maritime.

After confirming the settlement of a population, it is customary to disperse at a similar rate and with similar characteristics to that observed in nearby basins, According to Francisco Oliva, professor at the University of Murcia and coordinator of the Life Invasaqua project to fight against invasive aquatic species.

Given its high reproductive capacity (a specimen can release more than 1 million larvae per year) and the absence of certain predators, it is expected to rapidly colonize affected reservoirs, Oliva warned, warning that it is in a basin like the delta. Segura, the socioeconomic impact could be disastrous for agriculture.

Some confederations have already spent more than 30m euros on the direct management of the species. and a study in the Hydrographic Confederation of the Ebro announced that indirect losses from zebra mussels amounted to more than 1,600 million.

According to him, the reduction of the reservoir level and extensive sampling to determine the true extent of the population will need to be added to the temporary prohibition of activities that could lead to the expansion of larvae into other reservoirs or aquatic areas. systems such as navigation or sport fishing.

“It is very likely that this species will colonize the Segura basin via the Tajo-Segura transfer.. For years, scientists and technicians have warned of the need to constantly filter the flow that reaches the Talave reservoir from areas infected by zebra mussels in the Júcar river basin,” he complained.

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Environment department contact address:crisclimatica@prensaiberica.es