[Animal] The poor state of Catalan rivers threatens the death of native fish

[Arben]

 

Eels are dying at the mouth of the Francolí, in Tarragona. Some of them accumulate in ponds to drain the last stocks of water. This scene has been repeated in recent days and could be a foretaste of what will happen to other rivers and streams in Catalonia if the drought does not stop.

In the case of Francolí, however, the lack of water is not the only one responsible. At least this is what ecologists who follow the state of the river on a daily basis say: "The big problem is that more water is used than expected for industrial and municipal uses and the flow is not strong enough to reach the sea."

Images like these, caused in many cases by the degradation and exploitation of rivers, can be replicated in more parts of Catalonia if water scarcity persists. "The streams are dry and, although it may not seem like it, they are spaces where a surprising amount of biodiversity is concentrated," Álvarez details.

 

 

The lack of rain has consequences, for example, in several sections of the Tordera. "There are points where the river is maintained by the contribution of the treatment plants, but in others it is no longer", warns Sònia Sánchez, a technician from the Rivus Foundation. The members of this entity have detected eels in the lower course of the Besòs or sticklebacks in the Tordera (two threatened species): "They are fish used to ups and downs in water reserves, but so much scarcity can complicate their lives."

Despite these two encouraging findings, the general trend is rather negative: the first analyzes of the Rivus Foundation already show a regression of native species such as the mountain barbel or the chub. The dominators, in the Tordera, are invasive species such as minnows. In the Besòs, the presence of exotic specimens is even greater: Ebro catfish, carp or shrimp are the main inhabitants of the river.

In the secondary streams the scenario is even more worrisome. A good example is what happens in the Vallvidrera stream, where a research team from the UB has collected data to prepare its annual report. The ecological quality of this ecosystem is deficient and the flow is very weak. But the worst thing is the sharp drop in the number of fish, compared to previous years: they have only detected two native species: the redstart barbel and the eel (a single specimen). The situation, according to the Collserola natural park, is critical.

 

https://www.elperiodico.com/es/sociedad/20230413/mal-estado-amenaza-muerte-peces-sequia-catalunya-85943737