Evaluation of the bioaccumulation potential of alizarin red S in fish muscle tissue using the European eel as a model.

For fish stock management and large-scale stocking programs, the chemical substance alizarin red S (ARS) is an important tool to mark fish permanently. Equally, for the IUCN red list species European eel (Anguilla anguilla), ARS is proven to be the most promising option for mass marking. ARS binds to calcified structures (i.e., bones and otoliths) and can be detected using a fluorescence microscope. Despite the frequent application of ARS, not only for eels but also for fish in general, until today, no study has evaluated its bioaccumulation potential. Therefore, the German Federal Risk Assessment Authority was unable to classify ARS as harmless because of a potential risk to consumers' health. Using the technique of liquid chromatography mass spectrometry, an ARS detection protocol was developed and the bioaccumulation potential of ARS in European eel muscle tissue was estimated. A detection limit of 8.9 µg kg-1 could be reached by optimizing the detection method in fish muscle tissue. In the current study, 250 eels between 6 and 57 cm of total length have been analyzed for ARS between 0 day and 3 years after the marking process. The highest concentration of ARS (6056 µg kg-1) was observed immediately after marking in the smallest length class. Only 1 year after the marking procedure, the ARS concentration was below detection limit. A new method for ARS detection in fish muscle tissue, followed by utilization on marked eels, was able to show that the bioaccumulation of ARS in edible fish muscle was highly unlikely.