Development of an Individual Based Larval Model (ILAM) for Riverine Ecosystems II: Model Implementation and Validation in a Racetrack Flume

Past model studies assumed larvae to behave like simple passive particles. However, in a previous laboratory study (part I: Determination of movement patterns in a racetrack flume and model development) this assumption was shown to be insufficient for riverine ecosystems. Hence, a new concept of an individual based larval model (ILAM) was developed in combination with an existing 3D numerical model. It attempts to enhance model predictability in comparison to larval dispersal models based on simple numerical passive particles. This contribution presents the implementation of the model ILAM within an existing software tool (RSim-3D) and a validation study conducted in a racetrack flume, representative for a shoreline of a river. A characteristic riverine fish species (Chondrostoma nasus, Nase Carp) was used as target species. In terms of model validation, observed trajectories of individually released larvae were compared with computed trajectories. Longitudinal and lateral movement, height distribution as well as several active or passive movement patterns were considered over time. As a result, the larval model was implemented successfully and it was found to represent larval upstream and downstream moving patterns determined in the laboratory experiment. In the future, the applicability of the model will be tested in the River Danube.