Abstract
The quagga mussel (Dreissena rostriformis bugensis) is an invasive alien species present in many aquatic ecosystems. Although this species is known for its ecological and economic impacts, there are still significant gaps in our knowledge of its ecophysiology. This is particularly true when its growth rate under natural conditions is considered. Using a photogrammetry-based approach, we assessed bivalve growth in Lake Geneva during different seasons and for a variety of habitats. Based on the recorded changes in maximum shell length analysed during the period of this study (winter and spring 2023-2024), we measured average growth rates ranging from 0.142 ± 0.099 mm day(-1) for individuals smaller than 10 mm to 0.089 ± 0.071 mm day(-1) for larger individuals. The size class-dependent growth rate was analysed on the basis of the time of year, the type of environment (depth, substrate) or, again, the temperature. Our results reveal that the growth rate, obtained in situ and without manipulation, primarily depends on size and is independent of temperature or habitat within the studied range. This growth capacity in Lake Geneva is the highest found to date and is likely to explain the invasion success of this species.