Geoparque Mundial UNESCO

09 Ibor River (Barbel Spawning)

Geoparque Villuercas > 09 Ibor River (Barbel Spawning)

FAUNA

Every spring—typically in April, when the Ibor River has a good flow but is not in flood—barbel migrate upstream from the Valdecañas reservoir (on the Tagus River) in search of optimal spawning grounds to reproduce and ensure the survival of their offspring. This vital journey is reminiscent of the migrations seen in salmon rivers elsewhere on the Iberian Peninsula.

During this trek, the barbel battle against the current in an exhausting endeavor that takes them many kilometers upstream toward the headwaters, where the water is cleaner and richer in oxygen. Along the way, adult males can be easily identified by the white, bump-like growths that develop on their snouts. Upon reaching the spawning grounds, the females use their caudal (tail) fins to excavate small nests among the stones, where they deposit their eggs. The males compete to fertilize as many eggs as possible, posturing toward one another with sudden, yet harmless, movements. By the end of June, as water levels drop and temperatures rise, the spawning season concludes, and the barbel return to the Valdecañas reservoir, where they typically reside and feed.

FLORA

Along the banks of the Ibor, you will find a cool environment shaded by groves of alders, ashes, and willows. These areas are home to species such as otters, pond turtles, and kingfishers—as well as the American mink, an invasive species that is spreading throughout the rivers of the Geopark.

 GEOLOGY

An exceptional place to observe this springtime migration of barbel is in the vicinity of the Mesas de Ibor Bridge (also known as the Puente de las Veredas). Here, one can also see large, deep, circular rock basins—known as “giant’s kettles”—carved into granite blocks by the erosive action of water carrying small rocks. This area serves as a prime example of a surface-exposed granitic batholith, where the bedrock (granite) has undergone erosion—through both chemical and mechanical weathering—resulting in rounded boulders, “perched rocks,” “mushroom-shaped rocks,” and an extensive network of fractures (joints).