The construction of a dam not only changes the landscape but also has consequences for the aquatic ecosystem.
Read The damming of rivers by the construction of a dam has a direct influence on the body shape of aquatic creatures. The carp-like fish of the species Cyprinella venusta change their shape over generations to cope with the new life situation. This is what US researchers have found in the study of freshwater fish taken from both running waters and reservoirs. Accordingly, the fish adapt to the changed conditions of movement in stagnant water within a very short time by the transformation of their body. Changes in prey behavior may also play a role. The scientists report this to Travis Haas of Tulane University in New Orleans. There are currently more than 79, 000 dams in the US alone. The construction of such a water reservoir is not only a profound incision into the landscape, but also has consequences for the aquatic ecosystem: The damming of the water transforms a river into a stagnant water. A completely new challenge for aquatic organisms, for example, they have to cope with the lack of the usual current. Travis Haas and his colleagues found that fish living in reservoirs of the order Carp-like species Cyprinella venusta, also called blacktail shiner, have changed their body shape over several generations.

To do so, the scientists studied waters in the Mobile River Basin in the southeastern United States, a 113, 000 square kilometer area with 34 dams distributed in the area. To rule out natural differences in physique, the more common the farther the populations are geographically apart, the researchers studied only fish from adjacent rivers and reservoirs. From their living in running waters conspecifics located in reservoirs fish differed in several points: Particularly striking was the smaller head of the fish from the reservoir and their narrower body in contrast to the wider river fish. In addition, the dorsal fin was further forward on the body and was also much shorter at the base. The eyes were a bit lower and more in the direction of the belly. In addition, the scientists found a relationship between the size of the reservoir and the size of Cyprinella venusta.

For the researchers, the changes in body morphology are a direct response to the new environment. They suggest that damming water has put a lot of evolutionary pressure on aquatic life. The changes in body shape have a direct impact on the fitness of the fish. For example, the changes identified by the researchers as morphological shifts affect, for example, the nature of the movement of the aquatic inhabitants. Also, changes in the prey populations may be a trigger for physical transformation.

Travis Haas (Tulane University, New Orleans) et al .: Proceedings of the Royal Society, online pre-release, doi: 10.1098 / rsbl.2010.0401 ddp / science.de? Gwydion Brennan ad

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