Performance of a Recirculating Aquaculture System Utilizing an Algal Turf Scrubber for Scaled-Up Captive Rearing of Freshwater Mussels (Bivalvia: Unionidae)

To develop a system supporting rapid growth of juvenile freshwater mussels, a recirculating aquaculture system was designed and built at the Laboratory for Conservation Aquaculture and Aquatic Ecology, Virginia Polytechnic Institute and State University. The system included a rectangular trough tank, a sump (biofilter), a pump, a microalgae drip feeder, and an air delivery system. An algal turf scrubber (ATS) was evaluated for its potential to maintain and improve water quality within the system. Growth and survival rates of juvenile rainbow mussels Villosa iris after 90 d were compared between system units with and without ATSs. Flow rate through the culture units was approximately 23.3 L/min. Results showed no statistically significant differences between the growth and survival rates of juvenile mussels reared in systems with ATSs and those reared in systems without ATSs. Ammonia and nitrite levels were low and did not differ among treatments. However, systems with ATSs exhibited significantly lower levels of nitrate and phosphate than systems without ATSs. Our results show that freshwater mussel culture systems can be scaled up to increase production and that the use of ATSs may help to maintain *Corresponding author: [email protected] Received February 4, 2013; accepted July 12, 2013 water quality in recirculating aquaculture systems during longterm culture of freshwater mussels. North America contains the greatest diversity of freshwater mussels in the world—nearly 300 species (Williams et al. 1993; Neves 1999). However, about 70% (213) of the North American species are listed as endangered, threatened, or of special concern, and nearly 35 of these species are considered extinct (Williams et al. 1993; Neves 1999). Causes of population decline include habitat loss and destruction from impoundment of rivers, excessive sedimentation, water pollution, dredging, and other anthropogenic factors that affect the natural structure and function of free-flowing rivers (Neves et al. 1997; Neves 1999; Jones et al. 2005). Conservation of freshwater mussels has become a priority in the United States, and conservation measures include the propagation and culture of endangered mussel species in order to augment existing populations and 543 D ow nl oa de d by [ V ir gi ni a T ec h L ib ra ri es ] at 0 8: 44 0 2 O ct ob er 2 01 3