Canadian Farmed Oysters
Species farmed…
In New Brunswick, Prince Edward Island and Nova Scotia, the primary oyster species farmed is the American oyster (Crassostrea virginica)– also known as the Atlantic, Malpeque or Eastern oyster. In British Columbia, the primary farmed species is the Pacific oyster (Crassostrea gigas).
Where they’re farmed…
Canadian oyster production is distinctly divided between two regions: in 2013, 56% of the volume of Canada’s oysters was produced in BC; the remainder was produced in Atlantic Canada.
How they’re farmed…
The production cycle on a Canadian oyster farm begins with the collection/production of oyster larvae. In both Atlantic and Pacific Canada, some farmers collect the larvae in the wild. However, larvae are increasingly produced in controlled hatchery facilities from spawning adult broodstock. The larvae are kept suspended in tanks by circulating water – and in a few weeks they transform into tiny seed. The seed is essentially a very small version of the adult oyster.
Once the seed reaches an appropriate size, it can be transferred to the ocean for final grow-out. However – in British Columbia – before final grow-out the oyster seed is often transferred to a ‘floating upwelling system’ (referred to as a ‘flupsy’) that is housed on a raft on the ocean. The seed are kept in compartments on the flupsy whereby nutrient rich ocean water is circulated – thereby allowing them to reach a larger size before the final grow-out phase.
When the seed is ready for the grow-out phase, it is transferred to the ocean where it may be reared in one of a variety of systems:
- Beach or seabed culture: Individual oysters are ‘planted’ on the ocean floor. This form of farming has been ongoing in Canada since the 1800s and the first aquaculture leases granted were for oysters in the 1850s in Prince Edward Island for this type of farming.
- Tube culture: The flupsy stage is not used for tube culture. The larvae are allowed to set along lengths of plastic tubing or rope- where the seed then naturally attaches itself to the surface. The tubing/rope is then vertically suspended from a secured flotation device (e.g. raft or buoy) in deep subtidal water.
- Raft culture: Oysters are placed in trays which are then suspended from a secured flotation device (e.g. raft or buoy) in deep subtidal water.
What they eat…
Shellfish farming requires no input other than providing a clean environment and limiting predation. Oysters are filter feeders: they obtain all their required nutrients by drawing sea water through their gills and filtering out naturally occurring tiny plants and animals called plankton. Oyster farmers therefore do not need to feed their stock, and rely solely on natural food supplies.
Why they’re environmentally sustainable…
Oyster farming is, by definition, green and sustainable. Oysters cannot tolerate the discharge of sewage or other toxins; the presence of oyster farming, therefore, often results in increased awareness and monitoring of coastal waters.
In addition to being important modulators of nutrient cycles in ecological systems, farmed oysters help to reduce greenhouse gases by removing carbon dioxide from the ocean for shell formation.
Oyster farming is endorsed by environmental groups such as the Audubon Society, Monterey Bay Aquarium’s Seafood Watch and Eco-Fish.
Farmed shellfish improve water quality by filtering microscopic particles from the water. A single oyster can clear over 50 litres a day, retaining particles as small as 2 microns – even a small oyster farm can clean more than 350 million litres each day, reducing turbidity, increasing light penetration, improving water quality, and reducing anoxia (low oxygen).
Many shellfish farming companies in Canada are certified to one or more third-party certification program that assures consumers that they are purchasing high quality, sustainably produced shellfish.
Did you know…
Oysters are said to have aphrodisiac qualities. Some have related this phenomenon to the excellent nutrient content of oysters – especially vitamin E and zinc. Others say the aphrodisiac qualities are due to the dopamine content of oysters. Dopamine is a vital element that governs brain activity and influences sexual desire.
The first bottom leases for oyster farmers were actually provided to Nova Scotia and PEI farmers prior to confederation in the 1860's.
