Short-term breeding: releasing post-parasitic juvenile Margaritifera into ideal small-scale receptor sites: a new technique for the augmentation of declining populations

The aim of this research was to assess the potential for augmentation of freshwater pearl mussel populations Margaritifera margaritifera through short-term captive breeding to early juvenile stage and thus avoiding the growing-on stage of juveniles in captivity, which can have a high mortality rate. Fish encysted with Margaritifera glochidia were transferred to a tank lined with a thin layer of river gravels. Juvenile mussels were left to drop-down into these gravels and were then transferred, with the gravels, into suitable habitat in their native river. Redox potential measurements and near bed flow velocities were measured in the tops and tails of riffles to determine the best potential areas to transfer the juveniles. Following a year in the wild, juvenile mussels were found to be living in the areas in which they had been placed. This technique is recommended for rivers with populations of Margaritifera that have lost habitat quality, but where preferential flows maintain some areas that are still capable of juvenile survival.