Design and evaluation of recirculating water systems for maintenance and propagation of freshwater mussels

A complete system for culturing, rearing, and holding juvenile and adult fr eshwater mussels (Unionidae) was designed and evaluated for use at hatcheri es and research facilities. The system includes air delivery. water conditi oning and delivery, algal culturing and automated algal feed delivery, and air-driven water-recirculating units. These systems are appropriate for hol ding and conditioning adult mussels for spawning, as well as for the grow-o ut phase of juvenile rearing. In a 41-d trial without water changes in 350- L water-recirculating units, we used 200 adult eastern elliptios Elliptio c omplanata (average biomass = 1.36 g dry weight/ L): mean values (mg/L) duri ng the trial were 0.02 for NH3, 0.01 for NO2, and 2.7 for NO3. An 8-L mini- recirculating water unit (MRU) also was designed and evaluated for initial culturing of newly metamorphosed juvenile mussels. Survival of juvenile wav y-rayed lamp-mussels Lampsilis fasciola cultured in the MRU was 27.2% at 2 weeks, but this survival was negatively affected by the presence of a preda cious flatworm Macrostomum tuba. Survival of the juvenile lamp-mussels thro ugh II weeks grow our in the 350-L trough recirculating water unit was 58.8 %. We recommend this overall system of holding and rearing adult and juveni le freshwater mussels for use at hatcheries and research facilities because it is effective. low in cost, and easily maintained.