The freshwater pearl mussel Margaritifera margaritifera is a highly specialized, sensitive and critically endangered freshwater bivalve with a complex life cycle. An overview on the population status in Bavaria, Germany, one of the species’ main areas of distribution in Central Europe, is presented. Using the example of the freshwater pearl mussel and a Bavarian conservation project for this species, a scheme for the development of site-specific conservation concepts is discussed.

Due to a lack of natural recruitment, the freshwater pearl mussel is on the brink of extinction in many parts of its distribution area. As a consequence, several breeding programs are in operation, many of them using semi-natural rearing methods. Especially during early life stages, several types of rearing devices are used to raise juveniles. However, there is no systematic comparison of different devices. In our experiment, we compared Buddensiek cages and sediment boxes. Each rearing device was filled with 30 one-year-old individuals. At 10 sampling sites three Buddensiek cages and three sediment boxes were exposed. Exposure started in June 2016 and ended in May 2017. Overall, survival of juveniles was higher in Buddensiek cages than in sediment boxes with 40–93% compared to 0–87%. Growth was comparable in both field cages. The study site specific variation indicates that suitability of field cages is determined by environmental conditions. Furthermore, handling effort differs between the tested field cages. The optimal operating conditions for each field cage are discussed.

A significant part of freshwater mussel populations has strongly declined and many species are severely threatened nowadays. Captive breeding programs often form a central part of conservation strategies. As the life cycles of many mussel species include an obligate parasitic phase, host fish health is a crucial component of successful mussel breeding efforts. However, information about the safe application of fish therapeutants in mussel captive breeding is scarce. This article summarizes information about practical experiences in Europe. In total, eight different therapeutants were used to treat infestations of eight pathogens. Treatment success varied depending on pathogen and prevalence when treatments were initiated. Mussels did not seem to be affected by treatments, especially as long as they remained encysted. In a second step, Virkon S was applied to treat a fungal infection in tanks with brown trout (Salmo trutta) carrying encysted freshwater pearl mussel (Margaritifera margaritifera) glochidia and to disinfect juvenile mussel rearing containers. In both cases, mussels were not harmed and treated fish fully recovered. Results indicate that certain therapeutants can be used safely and successfully at different stages of breeding cycles. Nevertheless, there is still a lack of standard protocols, which would improve efficiency and the safety of treatments.