Overview
- The release took place in Wiesbaden-Biebrich at 11:00 on Friday, May 29, 2026, when roughly 50,000 maifish larvae were put into the Rhine with Hesse's agriculture minister and representatives from three other states present.
- Two Wiesbaden school classes helped with the event to raise local support and teach children about the species' life cycle and river restoration.
- Maifish larvae leave the river for the North Sea within their first year and mature at sea before adult fish return to rivers to spawn at ages three to eight years, so population recovery requires long lead times.
- The release is part of cross-state reintroduction projects that began in 2007 and combine repeated stocking, coordinated monitoring and habitat measures to overcome past declines caused by pollution, migration barriers and overfishing.
- Scientists say the program shows early signs of success because returning maifish have already been recorded and have reproduced naturally in the Rhine, but sustained monitoring and further releases will be needed to rebuild a self-sustaining population.