THE CULTURE OF JUVENILE FRESH-WATER PEARL MUSSELS MARGARITIFERA-MARGARITIFERA L IN CAGES - A CONTRIBUTION TO CONSERVATION PROGRAMS AND THE KNOWLEDGE OF HABITAT REQUIREMENTS

The culture of juvenile Margaritifera margaritifera in cages is shown to be a useful method of raising the early post-parasitic stages in suitable rivers for scientific or conservation purposes. Survival rates of caged specimens are equal to those of free-living juveniles, and growth is equal or slower than under natural conditions. Factors affecting the viability of caged juveniles are. length of the shell, colonisation of cages by aquatic insects and amount of free sediments accumulating in the cages. The influence of 12 water chemistry variables on the juveniles is analysed growth and mortality largely depend upon water temperature; there is a negative relationship between growth and eutrophication.