Translocated fish species can become as problematic as exotic ones, warns a UB study

July 26 () –

Translocated fish species can be just as problematic for native fish as exotic oneswarns a new study by the University of Barcelona (UB) published in ‘Science of The Total Environment’.

The analysis has focused on the ecological impact of native fish species introduced into hydrographic basins of its territory that do not correspond to it compared to the effects of alien invasive specieswhich are not native to any basin of the territory.

Thus, the study concludes that the quality of the habitat is essential for the conservation of native species, but the main novelty is that, after having taken into account the environmental variables -temperature, depth, water speed, pH or nutrient levels–, the results indicate that the translocated species had “potentially more important impacts on native fishes than alien species“.

And it is that, the research shows that the presence of translocated fish is associated with lower abundance and richness of native fish and with smaller native individuals, while the presence of exotic fish is associated with greater abundance and richness of native fish and individuals generally greater.

In this regard, the researcher at the Biodiversity Research Institute (IRBio) of the University of Barcelona and first author of the article, Alberto Maceda, has urged that “invasions by translocated native species be taken as seriously as those of exotic species in the systems studied, that is, the typical medium-sized Mediterranean streams and rivers”.

“It is not worth assuming that the impacts of exotic species are worse because they come from outside our borders, since we still do not have enough information to make statements of this type. In fact, we have a great lack of knowledge about diseases, hybridization problems, trophic competition, etc. that the translocated species can bring”, added the researcher.

The pioneering analysis, in which IRBio researcher Adolfo de Sostoa and experts Ralph Mac Nally and Jian DL Yen, from the University of Melbourne (Australia), have also taken part, has investigated the characteristics of different fish species in fifteen points in the basins of the northeast of the Iberian Peninsula, but it has focused on the family of cyprinids (Cyprinidae), one of the richest in species in the world and the most common in Europe.

LEGISLATIVE AND MANAGEMENT CHALLENGE

The conclusions of this study represent a considerable challenge for the current legislation and management of rivers, especially in the context of climate change, since the translocation of species is a frequent effect of water transfers between regions carried out by some countries to mitigate the consequences of global warming.

In this sense, Maceda has pointed to situations in which the same species has to be protected or eradicated depending on the hydrological basin in which it is found. “Species are normally declared problematic (invasive) in a political territory, but we can find that a species is native and has invasive populations in the same political demarcation. To complicate it even more, we can also find that a species is regressing in its native basin, but that, on the other hand, it is expanding in the basins where it has been introduced,” he detailed.

In this context, the researcher has pointed to the conservation of the habitat as the aspect in which the managers should influence more to conserve the native fish. “In general terms, We think that it is necessary to act with respect to the conservation of the habitat, because the benefits have multiple dimensions that, by rebound, can even make the native species better competitors than the exotic ones.“, he asserted.

Despite this general recommendation, he added that sometimes intervention against introduced species can also be a solution, especially if they are translocated native species, because they may have habitat requirements similar to those of the native species.

“Rivers with poorly preserved habitat are also the ones experiencing the most biological invasions and it is often difficult to distinguish between the effects of alien species and those of the habitat. However, in some cases the main detrimental effect is that of translocated native or exotic species and, therefore, acting and, if feasible, eradicating them completely, will surely be beneficial for the river”, he concluded.