Oysters

Pacific oyster (Crassostrea gigas - Latin name)

The Pacific oyster was first introduced to British Columbia waters from Japan around 1912 on the central coast of Vancouver Island. By 1942 the Pacific oyster had spread, and was successfully breeding in bays and harbours around southern BC. Native BC oysters, the Olympia oyster (Ostrea conchaphila) and the American oyster (Crassostrea virginica), are not used in aquaculture at this time.

What do oysters feed on:

Like other bivalves (shellfish with two matching shell halves), oysters are filter feeders. They feed on tiny plants called plankton, and other organic material, by drawing water in through an opening called a siphon. The water and nutrients flow in through the incoming siphon. The gills then trap the food inside the shell while allowing the oyster to filter out the water through a second outgoing siphon.

Oysters require a fresh, clean aquatic environment, and protection from predators. This includes protecting their equipment and netting from fouling by organisms and marine life that accumulate on the nets and trays, and compete for food.

Where are Pacific oysters farmed:

Vancouver Island and the Sunshine Coast are the main growing
areas, in particular:

• Jervis and Sechelt Inlets on the Sunshine Coast
• Barkley Sound on the west coast of Vancouver Island
• Cortes Island and Quadra Island
• with the largest production of Pacific oysters in Baynes
  Sound, on the east side of Vancouver Island.

How are Pacific oysters farmed:

Oyster farming begins with the production of oyster larvae from spat. Most larvae for the BC oyster industry come from spat produced using broodstock in controlled hatcheries.

The larvae are kept in tanks of circulating seawater and fed algae.

Within a few weeks the larvae are transformed into tiny seed (juvenile oyster) – a very small version of the adult oyster. After the hatchery phase, the juveniles are usually transferred to a nursery facility. In British Columbia – before final grow-out, the oyster seed is often placed in a ‘FLoating UPwelling SYstem’ (referred to as a ‘FLUPSY’). The FLUPSY is housed on a raft in the ocean. The seed or juveniles are kept in compartments on the FLUPSY, surrounded by the flow of the nutrient rich ocean water.

They remain there until they reach a larger size for the final grow-out phase.

Grow-out Phase:

When the seed is ready for the grow-out phase it is transferred and reared in one of the following ways:

• Beach or seabed culture: Individual oysters are ‘planted’
  on the ocean floor, spread out on a beach (intertidal areas) for
  growout or for hardening, and are covered by netting to protect
  them from predators.
• Tube or cultch culture: With this system the larvae are
  allowed to set along lengths of plastic tubing or rope. The
  seed then naturally attaches itself to the surface. The tubing/
  rope is vertically suspended from a secured flotation device
  (e.g. raft or buoy) in deep, subtidal water.
• Longline and raft culture: Oysters are placed in trays
  which are suspended from a secure flotation device (e.g. raft
  or buoy) in deep subtidal water (see diagram at right).

Optimal growing conditions:

12-18o C clean water of 25 ‰ + salinity. Oysters grown using deep
water culture grow three times as fast as intertidal oysters.

Harvesting the Pacific oyster:

Harvesting techniques range from hand-harvesting to crew-operated harvest vessels - depending on the volume of production and the type of grow-out system used.