Long-term retention of alizarin red S marks and coded wire tags in European eels

Abstract Durable marking of fish is an important prerequisite in many fish-ecological studies. In the course of a mark-recapture experiment with small European eels stocked in lakes, marking success rates above 95% were observed for coded wire tags and for alizarin red S marks 1–14 years after stocking. Both marking methods are therefore considered suitable for lifelong marking and tagging of eels, and application in long-term mark-recapture experiments.