What is the invasiveness of Hemimysis anomala (Crustacea, Mysidae) in the large deep Lake Bourget, France?

Abstract

Non-native species are a major threat to aquatic ecosystems and the assessment of their invasiveness may be limited by the diverse ecological features needed to be accounted for. In this study, we combined complementary features of the autoecology and trophic ecology of Hemimysis anomala in a large deep lake (Lake Bourget) to assess its invasiveness. It was present in more than 80% of the 23 sites explored, indicating an extensive colonization of the lake. The mysid exhibited at least two generations per year, and the median individual growth rate was ~ 0.04 mg dry mass day−1 and ~ 0.09 mg dry mass day−1 for juveniles and adults, respectively. Consequently, the daily production for a typical reproductive swarm could reach more than 250 mg dry mass day−1 m−2 representing an important hotspot of secondary production. Individual measurements of stable carbon (δ13C) and nitrogen (δ15N) isotopes highlighted a trophic ontogenetic shift and indicated that subpopulations of H. anomala could mainly rely either on benthic or pelagic resources depending on the slope of the site. Because of its extensive colonization, its high growth rate, and trophic plasticity, H. anomala exhibits a high invasiveness and may strongly alter the food web of Lake Bourget.