Oysters reproduce by releasing their eggs and sperm into the waters around them. Some of these eggs and sperm combine to form larvae. These larvae are free-swimming for a few weeks as they grow and develop. At a later stage of development, they begin sampling surfaces in search of somewhere suitable to attach. They are attracted to calcium-rich materials such as oyster shells.
Oyster life cycle diagram
The usual collection technique is to coat a collector with a calcium-rich material. The collector is then suspended in the water at a time coinciding with when the oyster larvae are ready to attach to a suitable surface. If timed correctly, oyster larvae will attach and begin to grow a shell. The collectors remain in the water for weeks or months to allow the oyster seed (baby oysters) to grow to about 6mm or larger in size.
Here are two different types of seed collectors
After the collectors are brought to shore, the oysters are removed, washed, sieved by size, and placed in tanks to grow in ideal conditions to the size of a quarter or larger. This seed is then placed in growth units on the farm.
Collection of naturally occurring oyster seed in no way impacts wild oysters. It is a proven technique commonly used on most oyster farms. Incidentally, a female oyster can produce up to 58,000,000 eggs annually…multiply that number by the vast number of oysters in the harbour and the number of larvae available is astronomical! We are interested in collecting only a very tiny fraction of this huge number. In fact, our farm is likely to increase wild oyster populations because oysters on our farm will add to the seed production of the entire harbour.
The process of seed collection does not involve disturbing, touching or removing wild oysters in the harbour.
The growth units we plan to utilize have been developed to improve upon several issues not addressed by gear commonly used on off-bottom farms throughout North America. Most relevant to our farm from the perspective of other stakeholders is the issue of visual profile. Our units are black in color, curved in shape, and float only a few inches above the water's surface. They will tend to blend in rather than stand out. Observers will see a pattern on the water, but it will be far less noticeable than other gear options. Furthermore, the distance to the nearest homes is ½ km so this pattern will be even less noticeable.
After the seed oysters have been on the farm grow sites for about three years, they will be of market size, 3” in length. At this point they will be removed from the grow sites and taken to shore.
To prepare oysters from Antigonish Harbour for market they must first be cleansed. This can be done in two ways. One method is to transport the oysters to an approved lease site to be left submerged for three weeks. This allows the oysters to purge any harmful contaminants. This technique is called "relay" and is a common approach in preparing oysters for consumption.
The second suitable technique is called depuration which, simply put, allows the oysters to purge any harmful contaminants in controlled conditions. The local company, Bio-Novations, markets depuration systems and we hope to use their technology as our system for preparing our product for market.
Packing / Shipping
The remaining steps to prepare the product for market are grading by size and shape, packing the product in shipping boxes, storing the product in refrigerated cold storage, and shipment to clients. None of these tasks involve any processing. There are no treatments applied beyond washing with seawater.
- Shellfish aquaculture — In praise of sustainable economies and environments & Open Access Publishing in the Journal of the World Aquaculture Society
- Scientific Research on Farmed Oysters - Via Fisheries and Oceans Canada
- Oyster Aquaculture and Restoration
- The Oyster is our "word." - The argument for farmed oysters
Thanks to Chen Shuhan for reference