Effects of algal density, water flow and substrate type on culturing juveniles of the rainbow mussel (Villosa iris) (Bivalvia: Unionidae) in a laboratory recirculating system

• Compared culture environments on the survival and growth of juvenile mussels
• The split-plot design was effective in conducting this multi-factor experiment.
• Juveniles had significantly higher survival and faster growth in fine sediment.
• Algae and flow were not significant factors in juvenile growth and survival.
• Demonstrated improvements in mussel culture using recirculating aquaculture systems

The effects of algal density, water flow and substrate type on the survival and growth of newly metamorphosed juveniles of the rainbow mussel (Villosa iris) were investigated in 40 l recirculating culture systems. A split-plot design with a whole plot factor combining algal density and water flow, and a split-plot factor of substrate were applied in this study to test the three factors. Juveniles reared in 4 juvenile culture units (550 ml) with fine sediment (< 200 μm), sand (300–500 μm), limestone gravel (800–1000 μm) and without substrate in each recirculating system receiving water flow at levels of 3.75 ml s− 1 or 7.5 ml s− 1; algae concentrations of 35,000 cells ml− 1, 87,500 cells ml− 1, or 175,000 cells ml− 1 were sampled every 10 days during a 30-day experiment. Substrate type significantly affected survival and growth of juveniles (p < 0.0001), while algal density and water flow had no significant influence on their survival or growth (p > 0.05). Juveniles had significantly higher survival and faster growth in a substrate of fine sediment when compared to other substrate types (p < 0.05). Escapement rate of juveniles exceeded 39% overall in culture units. Water quality was consistent throughout the experimental duration and within a suitable range for juvenile mussels. Results confirmed that fine sediment is the best substrate for juvenile culture in a laboratory recirculating system. The split-plot design was effective for conducting this multi-factor experiment and saved significant time and resources.