This diploma thesis is dedicated to the analysis of the migratory behavior of the Chi-nese mitten crab. It includes the implementation of a laboratory experiment to in-vestigate the causes of the failure of a crab trap and the conceptual planning of an ethohydraulic laboratory experiment to record the behavior of this invasive species in detail under controlled conditions.
Originally native to East Asia, the Chinese mitten crab was first detected in European waters in 1912 and has spread rapidly since then. Their migratory instinct and ability to cover large distances make it a particularly adaptable invasive species that has successfully established itself in various river systems. Its spread has significant eco-logical and economic impacts, including the destruction of fishing gear, damage to riparian structures and threats to native species. River systems with a connection to the North Sea are particularly affected, as they offer optimal conditions for the crabs to multiply and spread.
As part of the management strategies, various methods for catching crabs, including the Clancy project, were presented and evaluated. Furthermore, potential economic utilization options for the crabs are discussed.
A central component of the work is the implementation of a hydraulic laboratory test on a scale of 1:5. Through various experimental setups and the visualization of the flow with the help of beet juice, the flow conditions in the near field of a mobile crab trap could be analyzed in order to evaluate the effects of undercurrent and trap construction on the migratory behavior of the mitten crabs and to identify possible focal points for concept planning.
Based on the results from the full-scale test, a concept for an ethodhydraulic labor-atory test on a 1:1 scale was developed. The aim is to analyze the behavior of mitten crabs and the efficiency of crab traps under controlled, near-natural conditions. The experiments will focus on the interactions between current, sediment removal and trap functionality. Parameters such as migration speed, preferred routes and the effects of current speed and time of day on the behavior of the crabs will be inves-tigated.
The work shows that an integrated management concept consisting of monitoring, targeted removal and international cooperation is essential to contain the spread of the Chinese mitten crab in the long term. The results of this study will help to de-velop sustainable solutions for the protection of aquatic ecosystems and reduce the economic impact of this invasive species.