The fish comes from East Asia and was first discovered in the Ebro delta in 2001. Since then, it has occupied various parts of the river during its lightning spread, and is now definitively established.
The researchers do not rule out that it could occupy new areas within coming years and threaten the survival of native species.
The spread of the dojo loach (Misgurnus anguillicaudatus) or weather loach, as this oriental fish from the same family as the colmilleja (Cobitis Paludica) of Spain and Portugal is commonly known, contrasts starkly with the decline of native fish in the rivers and wetlands throughout the Iberian Peninsula, where 80% of species are threatened. The introduction of species from different areas is one of the most serious threats to the preservation of biodiversity, as explained in this study published in the latest issue of Biological Invasions.
“Aquatic ecosystems on the continent are the most seriously affected by invasive species, with fish populations being particularly devastated,” Miguel Clavero, the report’s lead author and researcher at the Forest Technology Centre of Catalonia, tells SINC. Nowadays, the majority of river basins throughout the Iberian Peninsula contain more foreign species than native ones.
The dojo loach is a small yellowish fish measuring around 20cm, which was first discovered in 2001 in the Sèquia Mare, a channel draining the rice fields of the Ebro delta, located on the northern hemidelta (left side of the river), although individuals were also seen in the river itself. Within a few years, the dojo loach has come to occupy most of the hemidelta and has moved towards the southern part, where it was first found in 2005.
Clavero explains that “today, the species occupies a minimum of 31 1x1km UTM quadrants within the interior of the delta, and several thousand individuals have been caught during operations to monitor ichtyofauna carried out by the Ebro Delta National Park”. There is a high probability of the species expanding towards new areas. In fact, the researchers say that in the spring of 2007 the dojo loach was detected in the basin of the River Onyar, which is a tributary of the River Ter, in an area very close to the urban centre of Girona.
Salinity is a barrier
Despite its rapid expansion, Clavero and his team have shown that the distribution of the dojo loach “seems to be limited by salinity”, as it only occupies waters with a low salt concentration. This is one of the reasons why the fish has not invaded lagoons, swamps and other natural wetland areas in the delta.
“The presence of the dojo loach, like that of many other invasive fish species in the Ebro delta, is linked to the continuous flow of river water channelled from the Azud de Xerta reservoir to irrigate the rice fields, which cover 60% of the surface area of the delta,” the researcher points out.
Introduction of species is a threat
The researchers believe that the dojo loach population first appeared in the Ebro delta “after some individuals escaped from tropical fish maintenance and distribution facilities”. Centres that breed and maintain exotic fish pose a serious danger and are “an epicentre of the biological invasion process”.
This fish could be responsible for parasitic platelminths becoming established in the area, and could indirectly compete for resources with native species. “Each addition of a new species to an ecosystem has an impact on its other inhabitants which, in the case of fish at any rate, are always negative,” stresses the scientist. In the lower part of the Ebro, the presence of the dojo loach could threaten the survival of the freshwater blenny (Salaria fluviatilis) and the colmilleja (Cobitis paludica).
The dojo loach or weather loach is, according to Clavero, one of the most recent introductions of an invasive species in the Iberian Peninsula. With a long, somewhat flattened body, it is a fish designed to live in waters with weak currents, where it feeds on snails and insect larvae. It can survive temperatures close to freezing, and tolerates very low levels of dissolved oxygen.
Although it is not so common in Europe, it is spreading in other parts of the world such as the Philippines, United States, Central Asia, Australia and various Pacific islands, where it is used as an aquarium fish, as well as for live bait and as a food source.
SINC Team | alfa
Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz
Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences