Aquatic Wildlife Conservation Center
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Mussel Production Systems at AWCC
Flow-through and re-circulating systems are used at AWCC to propagate freshwater mussels. The flow-through system uses river water that is filtered and heated before flowing to conical bottom tanks. Water exiting the tank is filtered by plankton nets to catch juveniles that fall from the fish. The benefit of this system is that it can hold many large fish and with fresh water there are no water quality issues.
The re-circulating systems feature tanks with individual inflow and outflow. Out-flowing water is filtered to collect juveniles and then pumped back through the system. This system is used to propagate species that use small fish as hosts. In addition, the use of re-circulated water makes the system easy to sample because the water is cleaner than in flow-through systems.
Juvenile Rearing
Juvenile mussels are counted and measured once they drop off the host fish. They are then placed in a rearing system to allow them to grow large enough to increase their survival in the wild. The rearing system includes an array of 5-liter tanks that are supplied with filtered water from the river. The water is filtered to eliminate predators that might consume small juveniles. Each tank is also fitted with a filter to catch any juveniles that might escape between sampling events.
Featured Species: Purple bean (Villosa perpurpurea)
The purple bean is a federally endangered species that can be found in the Clinch River drainage of Southwest Virginia. This small mussel got its name from the color on the inside of the shell. They can be found in shallow swift water of small streams with cobble substrate. The purple bean is a long-term brooder which means that they spawn in early fall and their larvae develop until early spring when they are released. The hosts for purple bean include darters and sculpin, small fish that spend their lives on the stream bottom.
This species was prominently involved in the chemical spill in the Clinch River at Cedar Bluff, Virginia in 1998. Approximately 156 purple bean were killed by the spill. Along with several other species, this was considered to be the largest kill of endangered species since the enactment of the Endangered Species Act. As a result this species has been targeted by VDGIF for restoration activities. In 2004, 1,272 purple bean were produced at the AWCC, of which 187 were stocked in the Clinch River at 2 and 6 months of age. So far in 2005, over 2,900 purple bean have been produced for release in the Clinch River.
Top: Purple bean (Villosa perpurpurea) male (top) and female (bottom).
Bottom: Six month old juvelnile purple bean produced at AWCC in 2004. These individuals range in size from 0.8 to 2.6 mm in length.