Manifesto for the defense of the Ebro against the invasion of the Zebra Mussel

Manifesto for the defense of the Ebro against the invasion of the Zebra Mussel

By Collective of Entities

The zebra mussel (Dreissena polymorpha) is a fresh and brackish water bivalve mollusk native to the Pontocassian region (Black Sea, Caspian Sea, Aral Sea, and the estuaries that flow into them). During the tertiary and quaternary periods, this genus differentiated into numerous local forms, endemic to these areas and in ecological balance, one of which was the zebra mussel.

The zebra mussel (Dreissena polymorpha) is a fresh and brackish water bivalve mollusk native to the Pontocassian region (Black Sea, Caspian Sea, Aral Sea, and the estuaries that flow into them). But this situation changed with navigation in the 19th century, spreading the zebra mussel to other areas where it was not in ecological balance and making it an invasive species in countries such as Great Britain, France, Italy or the United States.

Dreissena polymorpha has proven to be a tremendously damaging invasive species under certain conditions (it is among the 100 most harmful species in the world according to the IUCN). On the one hand, it is a perfect invader, capable of withstanding sudden changes in temperature and salinity and lasting several days out of the water, with which it can colonize other waters in the form of adhesions in boats or fishing equipment, as bait or traveling in the ballast waters of large ships. On the other hand, its rapid growth and biological cycle allow it to expand rapidly (in just 10 years it was able to colonize the eastern half of the US). It also forms colonies of very high density that line the bottom of the rivers.

This capacity has serious economic consequences: clogging of pipes, conduits and infrastructures, adhesions in boat hulls and engines, alteration of fauna and water conditions, etc. And even more serious ecological consequences: it decreases the dissolved phytoplankton, alters the composition of the bottoms and river waters and affects to a greater or lesser degree the species present in the rivers. Its effect on autochthonous bivalves stands out, on the one hand by reducing the available nutrients and on the other by fixing on them and causing their death by suffocation or sinking them to the bottom. Among those affected bivalves is, in the case of the Ebro, a species in serious danger of extinction: Margaritifera auricularia, for which the zebra mussel could mean its disappearance.

Once this species is introduced into an ecosystem, its eradication is no longer possible, it is an irreversible biological contamination of the natural environment. Prevention covered by strict compliance regulations, environmental awareness and scientific research are currently the only tools to combat the invasion of the zebra mussel in the Ebro basin, otherwise this serious problem will spread to the continental waters of the entire Iberian Peninsula.

For all the above, and considering that the Iberian Peninsula was free of this invasive species to date, the detection of zebra mussel specimens in the Ebro basin in the summer of 2001 was considered by the experts as a very serious threat to the Ebro basin and, by extension, for the entire Peninsula.

The seriousness of the event prompted the request for urgent measures to the competent bodies (Ebro Hydrographic Confederation and the affected Autonomous Communities: Diputación General de Aragón and Generalitat de Catalunya) by numerous scientific and conservation groups. Along the same lines, a report by the team of biologists of the Grup de Natura Freixe de Flix (Tarragona) elaborated for the General Directorate of Nature Conservation of the Ministry of the Environment during the summer and autumn of 2001 and delivered in December of that same year.

Considering that at the moment more than a year has passed since the appearance of the zebra mussel in the Ebro, several facts can be verified:

The populations of Dreissena polymorpha have experienced an exponential growth in their densities, especially in the Riba Roja de Ebro reservoir, and the affected section increases with the passage of months. Effects such as greater water transparency, an increase in underwater vegetation in the affected sections and an accumulation of decomposing organic matter in the river bed have also been observed. The autochthonous bivalves, in the sections with the highest densities, also have numerous attached zebra mussel specimens. On the other hand, the effects on water catchment infrastructures and hydroelectric plants have also become noticeable.

The scant and slow action of the competent administrations, which highlights the ineffectiveness in implementing the most important instrument to combat the invasion of the zebra mussel: prevention, carried out with rigor and protected by specific legal regulations .


The undersigned individuals, entities and groups DECLARE on the basis of the above points, that the Ebro basin (already affected) and other river basins of the Peninsula are facing the invasion by the zebra mussel (Dreissena polymorpha), in the face of an ecological and socio-economic threat of the first magnitude, in the face of which it is necessary that the competent organisms take urgent and effective measures without further delay.

For this reason, they demand, through this MANIFESTO, that the Ebro Hydrographic Confederation in direct collaboration with the affected Autonomous Communities, and with the participation of all interested / affected social groups, implement the action proposals as soon as possible ( 1) recommended in the report "Location and evaluation of a new biological invasion: the zebra mussel (Dreissena polymorpha) in the Ebro", of the General Directorate of Nature Conservation of the Ministry of the Environment, as well as other measures (2) and actions recommended by experts in the field based on the evolution of this biological invasion. Bearing in mind that these measures must be accompanied by the necessary budgetary and personnel allocations, so that they are truly effective.

(1) Proposals for action in the aforementioned report:

Prospecting of the Mequinenza reservoir.
Prospecting the bottom of the Flix and Riba Roja reservoirs.
Control of the movement of vessels and cleaning of vessels present in the infested area. Establish regulations in this regard.
Monitoring of the invasive population, including reproductive aspects.
Information to affected facilities on non-aggressive control methods with the environment. Establish regulations.
Information to users in general (commitment to periodically inform about the actions taken against the zebra mussel).
Monitoring of the affection of native molluscs and manual cleaning.
Control of sport fishing activities. Establish regulations.
Management of the river that avoids its proliferation in certain points (galachos and meanders) and the connection with other river basins.

(2) Examples of other possible recommended measures:

An official declaration of invasive species to control.
Organization of a special line of investigation to follow the invasion process and its ecological and economic consequences.
Approval of the recovery plan for Margaritifera auricularia and preparation of conservation plans for the rest of threatened bivalves.-

At the moment the adhered entities are:

Aljezar, Culture and Nature
AMAI- Ibón Environmental Agency
ANSAR- Naturalist Association of Aragon
ARCA- Association for the Defense of Natural Resources of Cantabria
Campero Channel- Antena 3
Subject COAGRET- Coordinator of People Affected by Large Dams and Transfers Ebro Vivo
Ecologists in Action Calatayud
Ecologists in Action Huesca
Ecologists in Action Zaragoza
Ecology and Development Foundation
GHG- Group of Invasive Species Grup de Natura Freixe (Flix, Tarragona)
IAA- Aragonese Institute of Anthropology Ofiverde de Torrero
Platform in Defense of the Ribera d'Ebre (Miravet, Tarragona)
SEO Aragon
SEO / BirdLife (Spain)
SEM- Spanish Society of Malacology
Aragonese Entomological Society

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Video: Zebras Risk Their Lives to Reach This Place Every Year. Nat Geo Wild (July 2021).