Over half freshwater fish species in Portugal’s rivers at risk

Study warns “perception is scenario could be even more worrying”

More than half of the freshwater fish species in Portugal are threatened with extinction, six of them critically-endangered, warns the Red Book presented in Lisbon yesterday.

Full name being “Red Book of Dulciaquic and Diadromous Fishes” (freshwater and migrating from fresh to salt water and vice versa), the work studied 43 fish species, 32 of which are resident and 10 migratory. It also confirmed the extinction of a species in Portugal, the sturgeon.

According to results of the project, which was coordinated by the Faculty of Sciences of the University of Lisbon, there are six species that deserve the greatest concern for being “critically-endangered“.

They include the Neapolitan lamprey, the Sado lamprey, and the western redhead. The group is joined by three migratory fish, the Atlantic salmon, the sea trout and the river lamprey.

Another 15 fish are in danger, including shad, saramugo and boga-portuguesa, while the project places five more species in the vulnerable category. As a result, 26 of native species – (60% of the fish generally found in Portuguese rivers) – are classified in one of the three threat categories of the International Union for Conservation of Nature (IUCN).

This latest Red Book follows one that was released 18 years ago.

Pedro Raposo de Almeida, director of the Centre for Marine and Environmental Sciences (MARE), who participated in both studies, said that the book is an instrument to assist the conservation of migratory and freshwater fish. He warned that the next 10 years are crucial in the management and conservation of aquatic nature because there is a risk of extinction of many species.

In the same vein, Filomena Magalhães, general coordinator of the project, emphasised “the strength of numbers”: only 19% of species have a classification that represents little concern.

She added there are species where assessment was not possible. These may be threatened and at risk of being lost.

“We lack data on populations, but the perception is that the scenario may be even more worrying. The costs of not acting are too great,” she stressed.

To illustrate the seriousness of the situation, Magalhães recalled the existence of Lusitanian endemism, which means that they do not exist anywhere else in the world besides rivers in Portugal, meaning if the species is lost it is the global loss of species, not simply a national loss.

Nine of the 10 Lusitanian endemisms face an extremely high or very high risk of extinction,” say the researchers, according to whom seven of the 17 endemisms of the Iberian Peninsula are also threatened.

To reverse the situation, Filomena Magalhães, professor at the Faculty of Sciences, defended as essential measures: habitat restoration; improving the conditions of aquatic systems and riparian areas; trying to counter interventions such as water abstractionconstant monitoring.

Structures such as dams, pollution from domestic and agroforestry sources and climate change are other dangers to fish in Portuguese rivers.

Of all 43 species analysed, only eight do not warrant any concern.

The Red Book project specifically focused on fish began in 2019. On Wednesday, the National Information System for Freshwater and Migratory Fishes, SNIPAD, was also presented in Lisbon. It is a platform that aims to gather and facilitate access to information on fish in Portuguese rivers and to support scientific research and conservation of these species.