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Freshwater mussels are declining throughout their range. Their important ecological functions along with insufficient levels of natural recruitment have prompted captive breeding for population augmentation and questions about the usefulness and applicability of such measures.This article reviews the current state of captive breeding and rearing programmes for freshwater mussels in Europe. It considers the various species, strategies, and techniques of propagation, as well as the different levels of effort required according to rearing method, highlighting the key factors of success.Within the last 30 years, 46 breeding activities in 16 European countries have been reported, mainly of Margaritifera margaritifera and Unio crassus. Some facilities propagate species that are in a very critical situation, such as Pseudunio auricularius, Unio mancus, and Unio ravoisieri, or multiple species concurrently. In some streams, the number of released captive‐bred mussels already exceeds the size of the remaining natural population.Rearing efforts range from highly intensive laboratory incubation to lower intensity methods using in‐river mussel cages or silos. Most breeding efforts are funded by national and EU LIFE(+) grants, are well documented, and consider the genetic integrity of the propagated mussels. Limited long‐term funding perspectives, the availability of experienced staff, water quality, and feeding/survival during early life stages are seen as the most important challenges.Successful captive breeding programmes need to be combined with restoration of the habitats into which the mussels are released. This work will benefit from an evidence‐based approach, knowledge exchange among facilities, and an overall breeding strategy comprising multiple countries and conservation units. [ABSTRACT FROM AUTHOR]

Sex ratio is an indicator of population health as unexpected biases may indicate potential threats. We studied nestling sex ratio in Black Stork Ciconia nigra populations in order to check potential biases and differences along east-west and north-south gradient across its distribution range in Europe. We also studied variation between years, and checked potential correlations with weather variables. The overall sex ratio of nestlings in Europe was nearly equal with a non-significant deficiency (47.1 %) of males, the larger sex. Although yearly fluctuations in sex ratio were detected, no significant effect of the year alone was found, only simultaneously with population and brood size. There was a tendency to have a higher proportion of female nestlings in larger broods, but the pattern was probably scattered by the effect of reduction of largest broods. Compared to Western and Eastern Europe, a significant deficiency of male nestlings was found in Central Europe (Poland), whereas no differences were found along the north-south gradient. We did not find any effect of temperature, but rainfall during the incubation period was negatively correlated with the proportion of male nestlings in Central (Poland) and Western Europe (France) whereas in North-Eastern Europe (Latvia) the same effect of the precipitation in pre-breeding period was found. [ABSTRACT FROM AUTHOR]