Captive Survival and Pearl Culture Potential of the Pink Heelsplitter Potamilus alatus

—Pink heelsplitter mussels Potamilus alatus were held at two bottom locations and suspended in pocket nets in a pond at the Freshwater Mollusk Conservation Center, Virginia Polytechnic Institute and State University, for 1 year to evaluate survival in captivity. Survival after 1 year differed significantly; the poorest survival (30.0%) was at the bottom of the deep end (2.5 m), and there was no difference in survival) at the shallow end (83.3%; 0.6 m) and in pocket nets (63.3%; 1–1.5 m). Monthly survival was inversely related to water temperature (R 1⁄4 0.72); the lowest monthly survival occurred in summer, resulting in a significant difference among the three locations. Differences in the mean glycogen content of mussels among the three containment locations and wild-sampled pink heelsplitter mussels were significant (P 1⁄4 0.001); the highest value was in mussels at the shallow end and the lowest value was in mussels at the deep end. We used pocket nets to hold surgically implanted mussels and measured glycogen reserves to monitor body condition and assess the potential of the pink heelsplitter mussel to produce nonnucleated and image pearls. Results of the pearl culture experiment in two ponds showed that nonnucleated pearls and image pearls with purple or purplish luster were successfully produced. There was no significant difference in pearl weight in mussels held in the two experimental ponds under different environmental conditions. Similarly, no differences in monthly survival rates of mussels were observed in either pond or among mussels with surgical implants and the no-surgery control mussels. Therefore, pink heelsplitter mussels can be considered a potentially suitable species for producing purple pearls in farm pond environments. A number of holding systems have been tested for suitability in maintaining mussels in captivity. Burress and Neves (1995) evaluated survival of 15 species of freshwater mussels in captivity in four separate pond sites in Virginia and reported that survival rates varied by species, captivity period, and habitat conditions. Dunn and Layzer (1997) also concluded that survival rates are influenced by captive facilities when comparing 20 species of mussels relocated to various types of holding conditions. In an evaluation of suspended nylon pocket nets and benthic dish racks, Gatenby (2000) reported that mussels held in pocket nets generally had higher survival rates than those in dish racks. Culture methods in commercial aquaculture include hanging culture (suspended nets in water) and bottom culture for marine bivalve production (Wang 1993; Wang and Tian 1998). Freshwater mussels used for pearl culture are usually held in net bags, net cages, or pocket nets that are suspended in ponds, reservoirs, or lakes for pearl production (Hua and Gu 2002). The advantage of hanging culture is that it maximizes the ‘‘cubic’’ water column by using the total water body instead of the ‘‘square’’ area in bottom culture. Moreover, hanging mussels are free of substrate, such that occurrence of disease caused by benthic microbes