Ex situ and in situ breeding and stocking of the European Mudminnow in Hungary: insights from a 15-year cycle of population reinforcement

Since 2011, our team has been engaged in the conservation biology of the European mudminnow ( Umbra krameri ), focusing on both ex-situ and in-situ methods. Our work includes (captive) breeding, egg incubation, and larval and juvenile rearing under controlled conditions and in natural habitats. Induced reproduction has been attempted in closed systems through the application of various hormonal treatments; however, these efforts have not resulted in success. In contrast, controlled natural reproduction has proven effective for producing offspring. An innovative spawning cage has been developed. This device facilitates the natural spawning of paired individuals, egg incubation, and larval rearing either directly at the original habitat of the parents or in reconstructed sites designated for population reinforcement. This method may result in higher survival rates compared to laboratory-based reintroduction. The spawning cage also allows the assessment of adverse environmental factors (e.g., sudden temperature fluctuations) during natural reproduction in the wild, providing insight into the reproductive success of local populations. Experiments on sperm cryopreservation, spawning substrate preference and feeding behaviour have been conducted under controlled conditions in recent years. Although only a small number of broodstock females are used annually, more than 8,700 individuals of various life stages (larvae, juveniles, adults) have been successfully released back into their original habitat or pilot areas. Currently, we carry out population maintenance and breeding in the artificial ornamental ponds of the Botanical Garden of the Hungarian University of Agriculture and Life Sciences (Gödöllő, Hungary), as most of the natural habitats of the species have dried out in recent years. Furthermore, a multifunctional device has been designed to integrate broodstock spawning, egg incubation, and larval rearing, thereby contributing to the sustainable reinforcement of U. krameri populations. Conservation efforts are currently ongoing.