Cliff, looked that up about the mussels life cycle and this is what I found:
The freshwater mussel has a unique life cycle, to include a short parasitic stage attached to fish. The life of a mussel can be partitioned into five distinct life stages: ( 1) a larva (called glochidium) developing in the gill of a female mussel, (2) a free-drifting glochidium expelled from the female mussel, (3) a parasitic glochidium attached to the gills or fins of a living host fish, (4) a free-living juvenile mussel, and (5) the adult mussel.