Modern Farming

The cool, nutrient-rich coastal waters of British Columbia’s vast coastline (over 27,000 km) provide the ideal location to grow some of the highest-quality shellfish found on menus around the world. As this map shows, shellfish farms are located primarily around the west coast of Vancouver Island and in the Georgia Basin. Historically, the most prolific areas for shellfish farming have been Baynes Sound, Cortes Island and Okeover Inlet.

Site selection for a shellfish farm is a process that can take up to three years because of the complexity of regulations and site management requirements. Many things are taken into account, including water requirements, such as water depth, current flow, proximity of other (local) resource users, salinity, water temperature and oxygen content. Other considerations are proximity to sources of pollution, local forms of fish in the habitat, the potential for algae growth in shallow water locations and accessibility to a transportation infrastructure that does not contribute to environmental intrusion or damage.

British Columbia shellfish farmers rely on a healthy environment and have been considered stewards of the ocean for over 100 years.

 Raft System

Shellfish farmers use rafts at deepwater sites to suspend culture systems used for different stages in the rearing of oysters, clams and mussels. For example, many shellfish farmers suspend tray systems that are used as nurseries for juvenile oysters and clams as well as for oyster growout. This method of “off bottom” farming is considered one of the most productive in the world.

Rafts must be built to withstand the severest weather, hold the weight of hundreds of dozens of mature oysters, and serve as safe work platforms for workers handling product. Important considerations in the design of a raft system include flotation, flexibility, stability, functionality, durability and capacity.

The raft system must be securely anchored to prevent movement and/or drift. Rafts are usually roped together and securely tied at three points on each raft and then anchored at each end. Anchor ropes will sway in the currents and slacken at low tides.

Longline Systems

Longlines are used worldwide to grow everything from scallops to seaweed. These systems are preferred in high exposure areas. They are productive and flexible enough to handle a variety of shellfish species as well as a range of culture systems. In a longline system, the farmer anchors a length of line at both ends, attaches a flotation and hangs culture systems on the line.

Nursery rearing as well as grow-out can be accomplished on longlines. Trays, tube modules and bags or cages can be hung in deep water for nursery rearing of clams, oysters or scallops. Seeded lines or socks (with adequate predator protection) are commonly suspended from longlines. Scallops are frequently grown-out on sunken longlines, in suspended lantern nets, or ear-hung directly on a down-line.

Intertidal Systems

Intertidal farming refers to systems in which shellfish are exposed to air during the low tide of each tidal cycle. These systems include both bottom (beach) and near-bottom (epibenthic) techniques.

Managing and maintaining productive intertidal growing areas is no different than land agriculture. The substrate will be cleared and prepared for planting. Both oyster and clam farming may require substrate improvement to reach acceptable levels of productivity. The area will be seeded and, in many cases, the seeded plots are protected from predators by overlaying them with mesh that is then secured into place. The plots will be tended regularly. Farmers will develop and maintain an inventory control system to know what was planted when and how it is performing.

Clams perform best in a substrate composed of a mixture of mud, sand, pea gravel and some shell fragments. Improvement for silted beaches may mean gravelling while for other sites it involves debris and rock removal.

In oyster farming, intertidal grow-out systems include beach distribution of seeded shell cultch as well as oysters grown on stakes, racks and intertidal longlines. Near-bottom methods have been adopted on sites where bottom conditions are not suitable for growing oysters; e.g., soft mud, silt. Nursery rearing of oysters on shell cultch or tubes may also be done intertidally.