L’Hàbitat de nàiades en el marc del projecte LIFE Potamo Fauna

Abstract

Unio mancus and Unio ravoisieri are two of the six species of naiads (freshwater mussels) that inhabit catalan aquatic ecosystems. Both are included in the project LIFE Potamia Fauna, which one of its objectives is to improve the population centers that exist in the rivers Ter and Fluvià since it’s seen a sharp decline in recent years. It is very important to study the naiads, because as they are filtering organisms have an important role in aquatic ecosystems. These two species are very similar in morphology and behavior, and it is known that live half buried in the sediment, usually of riverbanks and even sometimes they are hidden among the roots of trees. Actually, however, little is known about its habitat. That is why in this study it’s wanted to delve a little deeper and find out if there is some relationship between some environmental variable and the presence of naiads. 3

To do the research, ita was carried out in different sections of rivers Llémena and Ser, and som ditches of Banyoles and Brugent. Each part is divided into sections, where is sampled more data about naiads’s general inhabitat. Within each section, were also randomly chosen small areas of a meter in length, which has been a more specific micro-habitat of the naiads. With the data, we calculated the relative density of naiads and their average length in each case. Values taken into account when performing statistical calculations. The final results concluded that there is indeed a relationship between the density of naiads in a particular habitat and environmental variables. The following variables are a clear example of positive correlation in the rivers: a sediment composed of silt and clay, the presence of roots in the margins, the maximum depth and average depth. Verticality and cave are two variables whose together with the rest described play a key role when forming the micro-habitat more suitable for these two species of bivalves