Almost meter-long lamprey spotted again in the Guadalquivir: a rare find and an alarming sign. An adult lamprey nearly a meter long has been discovered in the Andalusian Rivera de Huelva—a species once thought extinct in the Guadalquivir basin. This finding highlights just how vulnerable Spain's rivers and their inhabitants are due to old dams and the invasion of non-native species.
In the Rivera de Huelva, one of the main tributaries of the Guadalquivir, biologists from the Doñana Biological Station (EBD-CSIC) recorded an adult sea lamprey nearly a meter long. This event is unique for the Guadalquivir basin: the last time this endangered species was seen here was in 2014, and since then it was considered virtually extinct in the region.
The sea lamprey (Petromyzon marinus) is an ancient anadromous species that is born in fresh water, spends most of its life in the sea, and returns to rivers to spawn. Its presence in the Guadalquivir has always been rare, and in recent decades—almost sensational. According to EBD-CSIC researcher Miguel Clavero, the discovery itself is a reason for cautious optimism, but real recovery is possible only if fish regain access to their traditional spawning grounds.
Dams and the disappearance of migratory fish
The construction of the Alcalá del Río dam in 1931 was a turning point for the lamprey and other migratory species. This and other hydraulic structures effectively blocked the route between the sea and the upper reaches of the rivers, leading to the disappearance not only of the lamprey but also of the European eel, Atlantic salmon, as well as the complete extinction of sturgeon (Acipenser sturio) and shad (Alosa alosa) in the region. Clavero emphasizes: for migratory fish, even a small dam becomes an insurmountable barrier.
Data on population decline
The lamprey situation is part of a global trend. According to the UN Convention on the Conservation of Migratory Species, since 1970 the population of freshwater migratory fish worldwide has declined by about 81%. In Spain, this process is particularly rapid due to the dense network of dams and the active spread of alien species.
Ribera de Huelva: the last stronghold
Ribera de Huelva is a unique area: it is the only major tributary of the Guadalquivir directly connected to the estuary and the sea. A mixed community is still preserved here: eels, shads, river barbels, crayfish, and three species of naiads. According to Clavero, this section is key to the survival of rare species in the basin.
However, even here the situation is unstable. In the lower reaches of the Ribera, invasive species such as the red American crayfish and the blue swimming crab have already established themselves, along with eight alien fish species, including the catfish, which is dangerous for local fauna. If the catfish becomes established, it could wipe out the remaining eel and lamprey populations.
What needs to be done to save them
EBD-CSIC researchers believe that saving the lamprey and other disappearing species requires decisive measures: control and removal of invasive species, restoration of river habitats, and most importantly — dismantling the old Alcalá del Río and Cantillana dams, which no longer have significant economic function but continue to destroy the ecosystem.
The issue of priorities in river protection remains pressing: today, most protected areas are concentrated in mountainous regions, while it is the lowlands and estuaries that are critically important for preserving biodiversity. As Clavero notes, “what is often most valuable to nature is not always the most picturesque.”
The context of this story is reminiscent of other successes and challenges in restoring disappearing species on the Iberian Peninsula: for example, the Iberian lynx recovery program recently achieved record results, as detailed in the article about the record breeding season of the Iberian lynx.
The appearance of lamprey in the Guadalquivir is not a guarantee of recovery, but it is an important signal: endangered species still have a chance, if the approach to managing rivers and ecosystems changes.
