Red Marten | Valencia (EFE).- The zebra mussel, present in 60 reservoirs in Spain and, in the Valencian Community, in the l’Albufera natural park, in areas of Mijares and Marina Baixa, is one of the invasive alien species that most Experts are concerned about its almost unstoppable expansion, at a rate of one million eggs a year, and the environmental and economic damage it generates.
This species, which was detected for the first time in the Community in the Sichar reservoir (Castellón), in 2005, when “a fisherman saw a bug he had never seen before”, has wreaked havoc in 35% of the reservoirs it manages the Júcar Hydrographic Confederation, as the head of the CHJ’s Water Quality service, Concha Durán, explained in an interview with EFE.
Its accumulation clogs waterways
The danger of the zebra mussel is not only that it displaces other native species, but also that they reproduce in such large numbers that their accumulation can clog water passageways, such as those that connect reservoirs with hydroelectric power plants or water treatment plants, and even in water transfers.
“An invasive species is any living organism that comes from another site, that is not autochthonous and that causes socioeconomic and ecological damage to the ecosystem that receives it,” explains Durán.
The ecological damage of the zebra mussel is caused to other native species, which it displaces, takes away phytoplankton to feed and the space in the rocks that the fish need to lay eggs, but the socioeconomic damage is, in this case, as worrying as previous.
“The zebra mussel reproduces very quickly and compact masses of organisms are generated, one on top of the other, which end up clogging any water intake,” he details about this species, which needs water with little current to live.
This is precisely the type of environment found in reservoirs and all the infrastructure connected to them. In fact, the presence of this invasive exotic species has been detected in different infrastructures such as the Cofrentes (Valencia) and Ascó (Tarragona) nuclear power plants, the water treatment plants of the Community, the Acequia Real del Júcar or the Júcar transfer pipeline -Vinalopo.
The consequences of these “plugs” range from the inability of a hydroelectric plant to generate energy to the inability to irrigate the fields when the mussel gets into irrigation ponds.
A long trip
In order to settle in Spanish territory, the zebra mussel has had to make a long journey from its place of origin, the Caspian Sea, and it is believed that it could have arrived in the water inside the engine of a boat or, in the larval state, in some live bait for fishing.
Since then, its expansion has been very rapid and, according to Durán, almost unstoppable: not only because a female lays a million eggs a year, but also because, in the larval state, the eggs are invisible, making it easy to drag them away in boats or in water transfers without realizing it.
In Spanish waters, moreover, they are comfortable. To reproduce, they need the water to be at 13 or 14 degrees, which in their place of origin can occur “two or three months a year” while here “they can be reproducing for six or seven months.”
bolt to invasion
For this reason, in less than 20 years there has gone from having zebra mussels in a reservoir throughout the national territory to being found in more than 60, and the difficulty now lies in stopping their expansion.
According to Durán, it is a complicated task: in open water, such as a reservoir or a river, it is prohibited to use chemical products, such as chlorine, which would affect the zebra mussel but also the rest of the species.
It is easier, he says, inside the facilities, where “you can add whatever you want because you are going to kill the mussel and only the mussel”, and there are alternatives such as chlorine itself or hydrogen peroxide.
And, in areas already affected, the measures are more like confinement, such as the one carried out for boats in reservoirs where this species is detected: after detection, they can only navigate in that reservoir, and not in other places, so as not to spread the larvae.
“A thief can enter a house through the big door, but also through any neighbor’s window or through a small window on the stairs, and with invasive species you have to control the big door, but knowing that the small ones are also important”, details Concha Durán.
Thus, these “small doors” for the mussel can be the drops of water in the motor of a boat, the traces in the wetsuits or even the ducks or birds that move from one reservoir to another.
Florida bullfrogs, blue crabs and turtles
According to the head of the CHJ service, the zebra mussel, in addition to being an invader, is an unattractive species because it cannot even be eaten, like other subspecies, “not because it is toxic, but because it practically has no meat.”
This is not the case of other species such as the blue crab, also an invader, which “can have up to 20 centimeters of head, 35 with legs included, and a lot of meat”, so “it is very good to eat”, as Durán assures. , which points out that “when an invasive species has a positive associated effect, nobody wants it to disappear.”
It has been easier to control the expansion of the bullfrog, a species that receives this name because its sound resembles that of these animals and that is detected thanks to the installation of amplifiers in the affected areas to listen to its particular croaking.
For their part, Florida turtles, known for eating each other in the Atocha pond, are another of the most common invasive species in Spanish waters, where they are released by “owners who get tired of having them at home”.
The release of exotic species that have been bought as pets or the deliberate introduction, especially for fishing, are some of the most common “doors” through which some of the 150 invasive alien species registered in Spain have entered.
Now, the purchase of these species is prohibited, but “a lot of disclosure” is needed, according to Durán, since many times these animals end up in national waters due to “lack of knowledge, not because of a bad idea.” EFE