Creixement i demografia de l’espècie invasora Phoxinus sp. en estanys d’alta muntanya dels Pirineus

Abstract

Cyprinid Phoxinus sp. is a non-native species of high mountain lakes of the Pyrenees. Its introduction has been done by humans, causing serious effects over those habitats and native species. The LIFE LimnoPirineus Project has as the main goal the improvement of these aquatic systems and the species that live there. The elimination and management of Phoxinus sp. has been done to achieve this objective, from which the samples have been obtained to carry out this study. The investigation done is based on the analysis of the growth and demography from the observation of otoliths, calcified bone structures located in the internal ear. Their visualization with binocular loupe allows the age determination of each individual, which will be related with the corresponding forkal length by a mathematical model named Von Bertalanffy. From this subsample used in the growth study and some estimation per proportions, the ages of each individual from samples not processed in the laboratory have been determined. With that, the analysis of the demography of each lake with the observation of the corresponding survival profiles and the instantaneous rate of mortality could have been done. Results show meaningful differences in the studied populations, both for growth and demography, being each lake’s limnological characteristics and morphometry the factors that can affect those divergences, also taking into account the possible presence of different species of Phoxinus sp. in all the lakes. In the case of Closell Lake, these growth and mortality rates have been close related to the fact that this population has been already exploited and has suffered a previous treatment. Concluding, this gesture has had a great success and has achieved the considerably reduction of the population