Saramugo has a strongly fragmented distribution restricted to the Guadiana River basin, between the Estena river close to Ciudad Real in Spain, and the Odeleite river in the south of Portugal – and in the Guadalquivir, but only in the Bembézar river.
In Portugal, it occurs essentially in small watercourses of the tributary streams of the Guadiana river.
The reduction in the distribution area and the population declines of this species, which took place from the 1970s onwards, is still happening today, with a very significant reduction in terms of abundance and distribution taking place, especially in the upper and central region of the Guadiana river basin in the national territory.
Adapted from the Saramugo Action Plan.
At the end of the last century, the saramugo occurred in the river sub-basins of the Álamo, Ardila (Ardila river and Múrtega, Safareja and Murtigão streams), Caia (upstream of the dam), Carreiras, Chança (upstream of the dam), Degebe (Pardiela and Pecena streams), Foupana, Odeleite (upstream of the dam), Vascão and Xévora. Nowadays there is a pre-extinction situation in the Upper Guadiana (Caia, Xévora, Degebe and Alámo rivers), and a significant reduction in its area of distribution in the Lower Guadiana. In spite of its fragmented distribution, the saramugo still has high levels of intra and inter-populational genetic diversity, suggesting that the recent decades of isolation have not yet had serious consequences in terms of genetic variability, even though the loss of genetic diversity cannot be excluded, taking into account that diversity levels of ancestral populations are unknown.
In addition, the low dispersal ability of this species has important implications for its persistence at the regional level, since the semi-arid region of the basin, in conjunction with growing human pressure on aquatic environments, predict bottlenecks and local extinctions which will happen more frequently if appropriate preventative measures are not put in place.
Translated by: Marta Cálix