Ex situ breeding and stocking of the European Weatherfish in Hungary and Romania

The weatherfish ( Misgurnus fossilis ) was first successfully bred by our research group in 2010. Since then, an induced spawning protocol combined with in vitro fertilization techniques has been applied, and experiments on sperm cryopreservation have also been conducted in this species. The stages and specific characteristics of embryogenesis and early larval development have been monitored and recorded. Larval growth and survival have been examined under various feeding regimes. It has been revealed that M. fossilis is capable of reproducing through parthenogenesis. Through further propagation of parthenogenetic offspring, F2 individuals exhibiting a unique hexaploid chromosomal structure—unobserved in natural populations—have been produced. In Hungary, approximately 2,000 individuals (both juveniles and sexually mature fish) were released into natural habitats during several stocking cycles between 2009 and 2016. Additionally, more than 16,000 individuals (larvae and juveniles) were reintroduced into the marshlands of the Olt River region in Transylvania (Romania) within the framework of a two-year conservation program. In 2024, we resumed our work related to the propagation of the weatherfish. These results contribute to the development of effective propagation, conservation, and reintroduction protocols for this protected and ecologically significant species.