The bleak (Alburnus alburnus) is a freshwater fish and such as the saramugo (Anaecypris hispanica) belongs to the family of cyprinids. It was a relatively recent introduction in the Iberian Peninsula and its expansion has been very fast. This fact, together with the lack of information on the impacts that this species may have on the native fish fauna, especially on the saramugo, evidenced the need to carry out studies in this field. Thus, a study was carried out that aimed to evaluate potential negative interactions between bleak and saramugo, specifically at the level of overlapping of preferential habitats, predation and competition.
| Saramugo (Anaecypris hispanica) |
 |
| Bleak (Alburnus alburnus) |
 |
The team from the University of Évora, partner of LIFE Saramugo Project, carried out sampling of the two species in a vast network of sites in the Guadiana river basin - a basin where saramugo is endemic. The presence of bleak, which currently occurs in many rivers in the Iberian Peninsula, was confirmed, in high abundance, in four sub-basins of the Guadiana River, with emphasis on the sub-basins of the Degebe, Caia, Xévora and the downstream sectors of Vascão riverside. However, presently, the range of distribution of the two species is not yet coincident.
Through the obtained results it is verified that the bleak performs in the water network that allow the rapid and progressive occupation of new areas, and that this mechanism is probably a key factor for its high invasive success. There was also a high overlap in the typology of occupied habitat and in the diet of individuals of both species.
In the laboratory tests, in a situation of coexistence there was no evidence of predation and competition between the two species. However, there have been significant changes in the behavior of saramugo, which may have indirect implications, particularly at the population level, if and when the species are coexisting in the natural environment.
The knowledge acquired through this study suggests that the future coexistence of bleak and saramugo may have negative effects on the populations of saramugo, mainly in scenarios of environmental constraint (eg habitat and food limitations) and high bleak densities.
However, in the present context, this invasive species does not appear to pose an imminent and superior threat to the conservation of the saramugo relative to that represented by the other invasive fish species in the Guadiana river basin. Even so, the results obtained in this action are essential for the minimization of potential impacts in the future, as they constitute an important support for the implementation of concrete conservation measures and improvement of the Saramugo habitat.
For more information on the bleak please check other news.
For more information on this projects Action please click here.
