Biological traits of an invasive specie, the pumpkinseed (Lepomis gibbosus), in an over-heated reservoir : reproduction, growth, longevity and predation ; Traits biologiques d'une espèce invasive, la perche soleil (Lepomis gibbosus), dans un réservoir artificiel aux eaux échauffées : reproduction, croissance, longétivité

The study of teleost reproduction is fundamental in order to understand the future of ichthyologic populations, determinant for the balance in aquatic environments, and this, in a context of global warming which will affect distribution zones of species as well as their reproductive strategies in order to guarantee survival of their progeny. Sexual maturation in pumpkinseed (Lepomis gibbosus) has been studied in an artificial basin in north-eastern France (Mirgenbach Reservoir) which receives over-heated water from the Cattenom nuclear power plant. Pumpkinseed, a centrarchid fish specie, is native to North America but has been introduced in Europe in 1880. Since its introduction, it has colonized the entire French hydrographic network. This specie, predominantly littoral, is already established in at least 28 countries in Europe and Asia Minor, but is currently considered to be invasive mainly in southern and central Europe. In our study, the reproductive effort was studied in both sex, using gonado-somatic index (GSI) and gonadal maturity stages obtained from histological observations. Growth and longevity have also been studied. A sample of 162 females and 157 males was collected for this work. In this context of warm thermal environment, sexual maturation is precocious compared to other pumpkinseed populations located at similar latitudes (age at maturity: 1 year), and the males mature one month before the females. The juvenile growth rate is high (LT>70mm at 1 year old), except for the small male cuckolders, but longevity (3 years) is lower than at the other sites in Europe (4 to 8 years). This precocity was also observed in other species at sites receiving over-heated nuclear plant discharge water, however oocyte abnormalities were observed which was not the case for the pumpkinseed population in the Reservoir Mirgenbach. The thermal conditions of the Mirgenbach Reservoir confer to this site a good opportunity to evaluate the consequences of the Global Warming on fish biology ; L'étude de la reproduction ...