Coastal dwellers have feasted on Mytilus edulis, a member of the Mytilidae family, since before recorded time. Mussels are bivalve shellfish that grow quickly and profusely, two traits that make them ideal for aquaculture. They have two identical, convex shells. These shells are elongate, triangular and joined by a rubbery hinge ligament on the upper side. A commercial sized mussel takes 18-24 months to grow to about 50 mm and at this size can pump 4 litres of water an hour.

Reproduction:

Mussels usually become sexually mature in late spring or early summer. Following some spawning stimulus, most mussels release some or all of their eggs and sperm in what looks like whitish or orange clouds in the water. Fertilization is external and in a very short time all the eggs are fertilized.

Life Cycle:

Once fertilized, it only takes five hours for the embryo to develop a small cilia and begin to swim. After 48 hours, it develops into a trochophore larva. It feeds on small phytoplankton cells and begins to develop the larval shell which has a distinct D shape. The next stage is the veliger larvae. In 3 to 4 weeks, the mussel grows to a quarter millimeter in size. The larva develops a foot and gills and is ready to change into a juvenile mussel. It settles on a suitable hard substrate, such as a rock, wharf or boat, extends the foot and withdraws the velum. Finally, it secretes byssus threads and anchors itself to the surface where it will grow into a mature mussel.

Feeding Habits:

Mussels are suspension feeders--they feed by actively filtering particles from the water. Phytoplankton cells are the main source of food and decomposed macrophytes or resuspended detritus may also supplement their diet.

Growing Techniques:

In eastern Canada, mussels are usually cultured on long lines. These are typically 600 foot ropes, anchored securely at both ends, and supported by floats tied at intervals along their length. Growers generally use concrete or salvaged railroad rails for anchors and lobster trap buoys for floats. Mussel farmers need lots of seed for a satisfactory harvest. Hundreds of plastic mesh or rope collectors are hung on the long lines just before the spat are expected to settle in the early summer. By fall, most settled spat have grown to about 15 mm. They are then stripped off the collectors and loaded into lengths of mesh tubing called socks. The socks are then taken to the farm and tied at intervals onto another long line where they will grow to market size. This takes 18 months to 3 years, depending on location, water temperature, and the availability of plankton.

Farming Areas:

The eastern shore of Nova Scotia from the Strait of Canso to Halifax has clean, cold water that supports blue mussel farming. The south shore area from Halifax to Yarmouth is characterized by good currents and warm water temperatures, which are also excellent for growing mussels. Coastal areas of Cape Breton also hold promise for mussel farming.

Conclusion:

For more information, contact Aquaculture (aquaculture@gov.ns.ca).

Nova Scotia Fisheries and Aquaculture
P.O. Box 2223
Halifax, Nova Scotia
Canada B3J 3C4

Phone: (902) 424-0356
Fax: (902) 424-4671