AS GLOBAL BIODIVERSITY IS DISAPPEARING AT ALARMING RATES, CONSERVATION PROGRAMS SUCH AS CAPTIVE BREEDING AND PROPAGATION HAVE BECOME COMMON PRACTICES IN SPECIES CONSERVATION. CAPTIVE REARED INDIVIDUALS ARE TYPICALLY RELEASED TO AUGMENT EXISTING POPULATIONS, REINTRODUCED TO THEIR HISTORICALLY OCCUPIED HABITATS, OR INTRODUCED TO LOCATIONS OUTSIDE OF THEIR HISTORICAL GEOGRAPHIC BOUNDARIES. FRESHWATER MUSSELS ARE AMONG THE MOST ENDANGERED ORGANISMS IN THE WORLD DUE TO HISTORIC AND ONGOING THREATS TO THEIR POPULATIONS INCLUDING HABITAT LOSS AND DEGRADATION, WATER POLLUTION, AND CLIMATE CHANGE. A GOAL OF CONSERVATION PROGRAMS IS TO PRESERVE NATURALLY OCCURRING GENETIC VARIABILITY WITHIN SPECIES, SO THAT THE SPECIES WOULD HAVE THE ABILITY TO ADAPT TO ONGOING AND FUTURE ENVIRONMENTAL CHANGES. HOWEVER, GENETIC ASSESSMENTS ARE LARGELY MISSING IN MUSSEL PROPAGATION AND RELEASE PROGRAMS. AS A BROADCAST SPAWNER, FEMALE MUSSELS CAN FERTILIZE THEIR EGGS WITH AVAILABLE SPERM IN THE ENVIRONMENT. AS A RESULT, MULTIPLE PATERNITY WITHIN A SINGLE BROOD IS EXPECTED TO BE COMMON. HOWEVER, TO DATE, A LIMITED NUMBER OF STUDIES HAVE INVESTIGATED MULTIPLE PATERNITY IN FRESHWATER MUSSELS, AND THE ASSOCIATIONS BETWEEN MULTIPLE PATERNITY AND GENETIC VARIABILITY WITHIN BROODS ARE NOT WELL UNDERSTOOD. FURTHERMORE, CURRENT CAPTIVE PROPAGATION PROGRAMS FOR FRESHWATER MUSSELS OFTEN FAILED TO ADDRESS GENETIC STATUS OF BROODSTOCK FEMALES, CAPTIVE REARED STOCKS, AND BOTH SOURCE AND RECIPIENT POPULATIONS. WITHOUT PROPER UNDERSTANDING OF GENETIC VARIABILITY AND POTENTIAL IMPACTS, CAPTIVE PROPAGATION AND SUBSEQUENT RELEASE WOULD NOT ONLY WASTE LIMITED RESOURCES BUT ALSO HARM THE EXISTING POPULATIONS AND ECOSYSTEMS. GIVEN A GROWING NUMBER OF CAPTIVE PROPAGATION EFFORTS, GENETIC MANAGEMENT GUIDELINES BASED ON SCIENCE ARE URGENTLY NEEDED TO MAINTAIN GENETIC VARIABILITY WITHIN PROPAGATED JUVENILES WHILE MINIMIZING POTENTIAL NEGATIVE CONSEQUENCES, SUCH AS INBREEDING, ARTIFICIAL SELECTION DURING CAPTIVITY, AND DOMESTICATION. THE GOALS OF THIS STUDY ARE TO ASSESS GENETIC DIVERSITY AND STRUCTURE OF NATURAL POPULATIONS, AND CAPTIVE REARED JUVENILES, ACROSS MULTIPLE ENDANGERED FRESHWATER MUSSEL SPECIES IN THE MIDWESTERN U.S. THESE ASSESSMENTS ARE AIMED TO UNDERSTAND GENETIC VARIABILITY WITHIN PROPAGATED JUVENILES AND POTENTIAL IMPACTS OF CAPTIVE PROPAGATION AND SUBSEQUENT RELEASE ON NATURAL POPULATIONS. WE WILL THEN DEVELOP GENETIC MANAGEMENT GUIDELINES FOR CAPTIVE PROPAGATION AND RELEASE PROGRAMS. THE GUIDELINES WILL INCLUDE RECOMMENDATIONS SUCH AS THE MINIMUM NUMBER OF BROODSTOCK FEMALES NEEDED TO BE COLLECTED AND MINIMUM NUMBER OF PROPAGATED JUVENILES TO BE RELEASED. THIS WILL BE PROVIDED TO PROPAGATION PRACTITIONERS TO FACILITATE SUCCESSFUL CONSERVATION OF FRESHWATER MUSSELS. INITIALLY, WE WILL CONDUCT A RANGE WIDE POPULATION GENOMIC ANALYSES TO ASSESS THE PATTERN OF NATURALLY OCCURRING GENETIC DIVERSITY AND STRUCTURE ACROSS MULTIPLE POPULATIONS OF AT LEAST 2 3 MUSSEL SPECIES. SECOND, WE WILL QUANTIFY GENETIC VARIABILITY AND STRUCTURE OF BROODSTOCK FEMALES, DERIVED GLOCHIDIA, AND CAPTIVE PROPAGATED JUVENILES TO COMPARE WITH NATURAL POPULATIONS. POPULATION GENOMIC DATA DERIVED FROM THIS PROJECT WILL BE ROBUST AND INCREASE OUR UNDERSTANDING OF GENETIC VARIABILITY IN THE REPRODUCTIVE AND EARLY LIFE STAGES OF FRESHWATER MUSSELS, WHICH ARE CURRENTLY MISSING.