A small fish, not exceeding 6 centimeters, causes real disasters in Spanish rivers. Introduced deliberately to Spain a century ago to combat certain diseases transmitted by mosquitoes, gambusia, or mosquitofish, has spread uncontrollably throughout much of the country. It threatens native river fish species such as the fart, which is of great importance and found only in the Iberian Peninsula, and is in danger of extinction.
this Gambusya holbrookiAlso known as the “mosquitofish”, it is a species native to the east coast of the United States and can live in fresh, brackish and brackish waters. Today, it is available in 30 countries across five continents, either for ornamental purposes, purely decorative or as a control measure against mosquitoes that carry certain diseases.
In the case of Spain, this aquatic species was introduced in 1921 to combat malariaAccording to the WHO, it is a “potentially fatal” disease transmitted to humans through the bite of infected mosquitoes, although it is preventable and treatable.
While Spain was declared malaria-free in 1964 and most cases have been imported since then, the truth is that this species is still abundant in nearly all the slow and warm waters of the Iberian Peninsula, particularly in parts of the country. most This, peninsula southwest, Mediterranean coast and Ebro basin.
This is because gambusia, which lives in slow-moving shallow water areas with lots of vegetation, Highly resistant to degraded and polluted environmentsfor example, where sewage is discharged or where there is a low concentration of dissolved oxygen. On the other hand, there are situations where local species cannot adapt.
Additionally, they are very competitive predators that often feed on dipteran larvae (flies, mosquitoes), copepods (small crustaceans) and aphids (aphids) that prey on the surface – hence their effectiveness against pests as they prey on their larvae. insects spawn and eventually snatch food from native species.
On the other hand, one of their high fertility, having 15 or 30 puppies per birtha reproductive capacity that can be modulated to correct population imbalances, increasing spawning when there is a deficiency or reducing it when it is excess.
Changes in the course of rivers with the construction of infrastructures such as dams, reservoirs and other sewers support their persistence as these exotic species live in hydric regions with a shallow flow.
biological effects
The established existence of this hardy species outside its natural habitat is thus the result of “biological warfare” waged at the beginning of the 20th century to control a parasitic disease in the country and the rest of the world. is when it reaches a high incidence.
It was then decided to prioritize public health over the protection of rivers and wetlands, as well as the status of native species living there.
But these decisions in the fight against malaria in Spain continue to have devastating consequences for hydrographic ecosystems today, especially for native species displaced by predatory gluttony and the adaptability of exotic species.
Between species threatened by mosquitofish fart highlights or Aphanius iberus, an endemic fish species from the Iberian Peninsula and one of the most endangered Spanish vertebrates; salt water or Aphanius baeticus (another fish that lives mainly in the Guadalquiver basin) and kickback or Gasterosteus aqualeatus. There have also been reports of native and endemic amphibians harmed by gambusia by preying on the offspring and tadpoles of this species.
According to the Spanish Invasive Alien Species Catalogue of the Ministry of Agriculture, Fisheries and Food, which includes Gambusia, species greed also affects the conditions of the environment of rivers and wetlands, as they contribute to reproduction. eutrophication processesThis means an increase in nutrients in the fresh waters of lakes and reservoirs, resulting in excess phytoplankton.
In addition, mosquitofish cause reduced oxygen availability and extinction of essential organisms of biocenosis (a set of plant or animal organisms living in a given environment), “leading to impoverishment of aquatic habitats and loss of biodiversity” and “a serious challenge to maintaining the balance of aquatic communities.” poses a threat.”
Gambusia is listed among the 100 most harmful invasive alien species in the world by the Union for Conservation of Nature (IUCN).
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