Identification of Host Fish and Experimental Culture of Juveniles for Selected Freshwater Mussel Species in Virginia

Host fishes for the state-endangered Tennessee heelsplitter (Lasmigona holstonia) and state-threatened black sandshell (Ligumia recta) were identified through induced infestations of glochidia on potential hosts. Largemouth bass (Micropterus salmoides), yellow perch (Perca flavescens), convict cichlid (Cichlasoma nigrofasciatum), platy (Xiphophorus maculatus), green sunfish (Lepomis cyanellus), rock bass (Ambloplites rupestris), redbreast sunfish (Lepomis auritus), and white perch (Morone americana) were identified as suitable hosts for L. recta. The banded sculpin (Cottus carolinae) and rock bass were identified as hosts for L. holstonia; striped shiner (Luxilus chrysocephalus), central stoneroller (Campostoma anomalum), and warpaint shiner (Luxilus coccogenis) were identified as potential hosts. Additionally, rock bass and bluegill (Lepomis macrochirus) were identified as potential hosts for the state-endangered spectaclecase (Cumberlandia monodonta), with numerous encysted glochidia present at 11 days postinfestation when the fish died.

Recirculating culture systems of different design were tested for suitability in juvenile mussel culture. In one system (high maintenance), juveniles of the wavy-rayed lampmussel, Lampsilis fasciola, were kept in culture dishes, and in the other system (low maintenance), the juveniles were kept in culture beds. At the end of the 16-wk culture period, the 31.3% (± 15.4) survival exhibited in the dish culture system was significantly greater than the 3.1% (± 2.8) survival in the bed culture system (P< 0.01, Tukey-Kramer). However, mussels grown in the bed system exhibited significantly greater growth (1.4 ± 0.50 mm height, 1.8 ± 0.76 mm length) than those grown in the dish system (0.86 ± 0.19 mm height, 1.1 ± 0.27 mm length) (P<0.01, Tukey-Kramer).

Using the high maintenance dish culture system and juveniles of L. fasciola, the influence of high (4.1%) and low (2.5 %) organic content in substrate, and high (250 mg/L CaCO₃) and low (50 mg/L CaCO₃) water hardness levels were assessed on growth and survival. After 15 wk, juveniles in the high water hardness treatment exhibited significantly greater survival and growth (44.2 ± 9.3% survival, 1.5 ± 0.28 mm height, 2.1 ± 0.41 mm length) than those in the low water hardness treatment (9.0 ± 7.9% survival, 1.3 ± 0.25 mm height, 1.8 ± 0.37 mm length) (P<0.01, Tukey- Kramer). Juveniles in the high organic substrate exhibited similar growth (1.41 ± 0.24 mm height, 1.96 +- 0.37 mm length) to those in the low organic substrate (1.39 ± 0.28 mm height, 1.94 ± 0.42 mm length). Juveniles grown in high hardness and high organic substrate had similar survival (27.4 +- 9.2%) to those in low organic substrate (25.8 ± 8.1 %).

For the culture of L. fasciola juveniles, I recommend using a culture system that is cleaned regularly (weekly), receives a consistent (daily) supply of algal food, has relatively even flow, and from which juveniles are easily sampled. I recommend culturing them in relatively hard water (~ 250 mg/L CaCO₃), in a substratum with some organic content. These recommendations may warrant modification for the culture of other freshwater mussel species.