Influence of Sediment and Algal Food on Cultured Juvenile Freshwater Mussels

The influence of river sediment and the suitability of algae as food for juvenile rainbow mussels (Villosa iris) and giant floaters (Pyganodon grandis) were investigated by rearing mussels on various combinations of green algae (Chlorella vulgaris, Ankistrodesmus falcatus, and Chlamydomonas reinhardtii), a commercial suspension of bacteria, and fine sediment (including autoclave-sterilized sediment). After 45 d, juvenile V. iris reared on sediment and algae had significantly better growth in shell length (552 μm) and survival (66.5%) than growth (437 μm) and survival (22.2%) of V. iris reared without sediment and fed only algae. A commercial suspension of bacteria added to a diet of algae also did not improve growth (462 μm) or survival (2.7%) of juvenile V. iris. Shell lengths of P. grandis juveniles fed algae and reared on various substrates (fine sediment, autoclaved sediment, and autoclaved sediment and bacteria) were similar among treatments. After 45 d, juvenile P. grandis reared on algae and fine river sediment achieved a mean length of 789 μm, representing a 2-fold increase in shell length, and 58.8% survival. Resident bacteria in riverine sediments seemingly were not essential to growth and survival of juvenile mussels. Mussels were observed pedal-feeding for 120 ± 30 (±SD) d; thus, sediment may serve as a substratum for pedal-feeding juveniles to collect food particles. After 272 d post-metamorphosis, V. iris juveniles reared on sediment and algae achieved a maximum shell length of 4520 μm (mean length of 2968 μm), representing a 17-fold increase in length, and 5% survival. After 195 d, juvenile P. grandis had a maximum shell length of 7846 μm (mean length of 4877 μm), representing a 22-fold increase in length, and 13% survival.