In recent decades, the presence of invasive species de peces in rivers, reservoirs and lakes in Spain has become one of the main threats to the aquatic biodiversity and the natural balance of ecosystems. The introduction —voluntary or accidental— de peces foreigners, due to human activities linked to both sport fishing and the keeping of exotic pets, has triggered serious problems for native species and socioeconomic activities related to the environment.
Far from being an isolated issue, the problem of invasive fish It affects numerous watersheds and natural parks, entailing everything from ecological risks to considerable financial penalties for those who violate environmental regulations. Analyzing some of the most recent and significant cases, it is possible to understand the magnitude of the problem and the urgency of adopting effective measures.
Fish that threaten Iberian fauna: featured species
Not all species de peces have the same invasive potential. In Spain, around a dozen species They have been identified for their particularly negative impact on the natural environment. The following stand out:
- Siluro (Silurus glanis): with bodies that can exceed 2 meters and an extraordinarily varied diet, it is considered the largest freshwater fish in Europe and one of the main predators of river ecosystems. Introduced in the 70s, it has established itself in rivers such as the Ebro and Guadalquivir, even threatening commercial fishing and protected habitats such as the Doñana area.
- Arctic Char (Salvelinus fontinalis): native to North America and known as brook trout, it invaded high mountain lakes and rivers after being introduced for restocking and sport fishing. Its presence threatens both native species and local amphibians, altering the chemical composition of the waters and causing hybridization with common trout.
- Snakehead fish (Channa spp.): Although it has not yet been detected in the wild in Spain, it is listed as an invasive alien species. Its extraordinary adaptability allows it to breathe air and survive out of water for days, which would facilitate its spread throughout the territory in the event of an accidental release.
- Pool cleaner fish or plecostomus (Hypostomus plecostomus): traditional in domestic aquariums, its trade and possession are now prohibited due to the risk it poses to local fauna if released into lakes or rivers, where it can seriously compete with native species.
- Other problematic species include sapwood, black bass, lucio, Gambusia, percasol y Asian goby, all of which are regularly removed from Spanish wetlands.
Behaviors, consequences and expansion of invasive species
The invasive success of these exotic fish It is explained by factors such as its voracity, high fertility and adaptability to different environments. For example, catfish and snakeheads show a much higher reproductive or survival capacity out of water than native species.
The environmental impact ranges from the direct predation on fish, amphibians and aquatic birds to an imbalance in food chains, competition for food, and habitat destruction. In high mountain waters, char has even altered nutrient cycles and raised phosphorus levels, affecting the reproduction of species that had never previously coexisted with predatory fish.
In regulated reservoirs and rivers, the massive presence of species such as carp and crucian carp —also invasive—causes mortality episodes due to sudden changes in flow, high temperatures, or when they attempt to colonize new spaces and encounter insurmountable obstacles, which requires removal campaigns to prevent water pollution.
The damage is not limited to the natural environment. traditional fishing activity and aquaculture suffer direct economic consequences due to competition and the introduction of parasites or diseases associated with these invasive species.
Institutional response and control strategies
Environmental authorities and managers apply different measures to combat the spread of invasive fish:
- Awareness campaigns aimed at fishermen, aquarium enthusiasts, and the public to prevent accidental or illegal releases.
- Implementation of massive removal and intensive monitoring programs in areas of special ecological value, such as high mountain lakes or reservoirs affected by occasional mortality episodes.
- Systematic removal of invasive species and return of native fish to their natural habitats, using methods that minimize damage.
- Enforcement of the Spanish Catalogue of Invasive Alien Species and associated legislation, which ranges from significant fines to prohibitions on possession, breeding, or trade. In some cases, fines for non-compliance reach up to €200.000, or even €XNUMX million if serious environmental damage is proven.
The autonomous communities also maintain specific surveillance and control regulations, especially in those areas where the consequences for biodiversity and the economy can be particularly severe. A paradigmatic example was the recovery of the Peñalara lagoon after years of work to eradicate char, allowing the return of endemic species of zooplankton and amphibians.
Prevention and action: the key to managing invasive species de peces
Experience shows that the prevention It is the most effective and least expensive tool against these species. Environmental education, along with early warning systems and clear action protocols, can prevent animals purchased for aquariums, used for sport fishing, or accidentally transported from colonizing our rivers and reservoirs.
In the case of the detection of a Invasive speciesThe recommendations are to never release them into the wild and to immediately contact wildlife protection services. There are official channels for returning exotic animals to avoid harm and penalties.
Control of these species is difficult due to the capacity for adaptation and reproduction of many of these fish, coupled with the absence of natural predators and the fragmentation of habitats caused by reservoirs and dams. Therefore, collaboration between public administrations, conservation organizations, and citizens is essential to reducing the spread of invasive fish and protecting Spanish ecosystems.
The introduction of invasive exotic fish into Spain's aquatic systems has required a redoubling of monitoring, recovery, and environmental education strategies. Citizen participation and preventive management are key elements to halting their spread and protecting the biodiversity of our rivers and lakes.