METHODS FOR LABORATORY CULTURE AND FIELD CAGING OF FRESHWATER MUSSELS.

1. water METHODS FOR LABORATORY CULTURE AND FIELD CAGING OF FRESHWATER MUSSELS. M. Chris Barnhart, Biology Department, Missouri State University, Springfield, MO USA The bucket systems are fed commercial marine algae suspensions (Reed Mariculture) at controlled rates via computer-controlled peristaltic pumps. Water is changed weekly. High mussel densities can be maintained. We have propagated mussels at Missouri State University since 1999 for research and for population restoration. We have developed several methods that facilitate host evaluation, captive propagation, handling, and grow-out.Details are available upon request. 1) AHAB systems. For host evaluation, commercially available multi-unit aquarium systems (Aquatic Habitats, Inc) were modified with gutters and recovery filters to enable daily recovery of transformed juveniles from individual host fish without the labor-intensive step of siphoning aquaria.  4)  Mussel silo: This portable cage system was developed for deployment of small groups of juvenile mussels in rivers.  Each silo consists of a concrete hemisphere weighing approximately 10 kg and containing a 5-cm diameter inner chamber with screen ends.  Water flow over the hemisphere creates a Bernoulli effect that draws water through the chamber.  Silos must be used on coarse substrate so that water can enter from underneath. Silos are stable during spates. They permit excellent growth in suitable conditions, and are useful for field bioassays. 2) Recirculating propagation systems (RPS) were developed for transformation of glochidia on groups of hundreds of host fish.  Each RPS incorporates paired 400-gallon conical-bottom tanks. A shared sump is equipped with a biofilter and with cod-end nets for recovery of juvenile mussels.  2 months growth in mussel silo 5)  Mussel bunker: A larger, less portable cage system used for grow-out of juvenile mussels in rivers.  Two concrete pads support a platform that holds 11-cm diameter chambers.  A perforated hood covers the chambers. Water flow over the hood creates a Bernoulli effect and draws water through the chambers.   3) Bucket rearing system. These are compact recirculating systems for captive grow-out of early juveniles.  Mussels are held in 2-part screen-bounded chambers (upper left) that are mounted in holes in the bottom of the upper bucket (center and upper right). Nesting the buckets creates upper and lower compartments (lower left). A small submersible pump moves water from the lower to the upper compartment and the water returns through the chambers.  (Barnhart 2006. Aquaculture 254:227-233.) Growout in our laboratory recirculating systems is practical up to lengths of about 5 mm, which can often be achieved in a few months. At that size, growth on algal diets slows. Rapid growth is reinstated by moving the mussels to a natural food supply by caging in rivers or ponds. Over the summer, some species can reach 4 inches length within 6 months (Potamilus alatus at right). Thanks to Frankie Thielen for the opportunity to present this poster, in absentia. For more information contact ChrisBarnhart@MissouriState.edu, or visit http://unionid.missouristate.edu and http://biology.missouristate.edu