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Universidad de Murcia (2018)

Biological response of invasive fish in a highly regulated mediterranean river basin (semi-arid environments SE Spain)

Amat Trigo, Fátima

Titre : Biological response of invasive fish in a highly regulated mediterranean river basin ( semi-arid environments SE Spain)

Respuesta biológica de peces invasores en una cuenca mediterránez altamente regulada

Auteur : Amat Trigo, Fátima

Université de soutenance : Universidad de Murcia

Grade : Doctoral Tesis 2018

Résumé partiel
This doctoral thesis is composed by four chapters and aims to increase knowledge about population plasticity of invasive fish in highly regulated basins of the Mediterranean area in semi-arid environments (SE Spain). For this, the study area has been the Segura river basin, whose natural hydrological regime presents strong seasonal fluctuations of flow and, in turn, it is one of the most intensely regulated Mediterranean basins in Europe. The target exotic species of this work are Gobio lozanoi Doadrio & Madeira 2004, Lepomis gibbossus (L., 1758) and Alburnus alburnus (L., 1758), which are widely distributed in the Segura River basin and have a high frequency of occurrence in the study area. These species have demonstrated a high ability to dispersion and establishment in rivers of the Iberian Peninsula and their biological plasticity has been proposed as an important factor involved in their invasive success. However, to increase knowledge about their biology and ecology in Mediterranean environments is still necessary. The main objectives of this doctoral thesis have been : a) to study intraespecific variability of the population traits such as relative abundance, population size structure, growth rates, reproductive investment and tactics, and fish status condition of target species, and b) to determine relationships between their population traits and environmental features, mainly assessing their variability throughout the longitudinal gradients and evaluating flow regulation effects at a river basin scale. The first chapter deals with the population plasticity of Alburnus alburnus along the longitudinal gradient of the river. The main objective was to study the intraspecific variability of their population traits and their relationships with environmental gradients along longitudinal gradients. The results showed that this species has rapidly spread in the Segura River basin and its high presence confirms the viability of its populations in river stretches. The size and age structure turned out similar to other Iberian locations, but much smaller than in its native areas. Longer residence time determined populations with larger size cohorts and older fish. Abundance, maximum length and growth in A. alburnus populations showed a negative significant relationship with the longitudinal gradient. The results support the hypothesis that the wide phenotypic variability in population traits of A. alburnus seems to play an important role in its invasive success in a highly regulated Mediterranean basin and, in addition, it also suggests that flow variability is an important factor conditioning population traits development. The second chapter studies the effects of flow on the populations’ size structure of four species. The main goal was to assess the effect of flow regulation on population size structure of freshwater fish belong to different ecological guilds throughout the longitudinal gradient of a highly regulated Mediterranean river basin. Different flow regimes and presence of artificial-flow habitats derived from anthropogenic impoundment affected fish condition and population size structure of the target species. The observed responses were species-specific in accordance with their ecological guilds. Natural flow regimes typical from Mediterranean basins were less suitable for typical species of stable environments (lentic habitats). However, the presence of flow regulation structures seems to provide more stable environments and possible refuges for individuals of these species. The third chapter deals with the reproductive strategy of Gobio lozanoi. The main objective was to analyse the reproductive traits and the energy balance strategy, during the reproduction phase, in an invaded Mediterranean basin in the southeast of the Iberian Peninsula. The gonadal activity was similar for both sexes and four reproductive stages were described in the reproduction cycle : quiescence, maturation, spawning and postspawning. The somatic condition in males was higher than in females, suggesting a higher energetic cost for females in reproduction. The species reached sexual maturity at early ages and showed lower fecundity and bigger oocytes than other Iberian non-native populations. Protein and lipid contents in tissues showed different dynamics during the reproductive cycle and the results suggest the presence of an intermediate strategy in the species which behaved more as an income-capital breeder.

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