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.
Our nursery is a novel and innovative concept designed and built by Ernie Porter P. Eng. and his family. It is an upwelling, land-based system that has 3.5' tall silos and relies on two electric water pumps to flow water through silos containing oyster seed. It is a flow-through system, the same amount of water that enters the system is returned back to the harbour completely untreated other than the filtering from the oysters. The oyster seed (baby oysters) in this nursery filter incoming seawater to feed and that clarified water flows back to the harbour.
The oyster seed in the nursery, just as the oysters on the proposed farm sites, filter their food from seawater flowing past. So, the oysters in the nursery will provide the same beneficial effect as those on the farm. They will remove phytoplankton, detritus, EWD pathogens, suspended excess nutrients and silt particles, leaving the water cleaner and clearer. In the process, they will excrete feces and pseudofeces that will not remain in suspension as readily as the fine particles the oysters ingested. These sediments settle to the bottom and contain converted forms of nitrate and phosphate nutrients that are more useful to marine plants like eelgrass, than the fine suspended particles residing in the water column. Also, the current adjacent to the nursery is among the strongest in the harbour, therefore dispersion will ensure wider dissemination of these sediments.
We plan, in the near future, to build sufficient solar capacity to enable this facility to run without carbon inputs. At this point, all the carbon sequestered in the growing shells will be a net benefit and in a small way push back on global warming.
Oyster seed in a silo.
The BOBR (Benefit Of Being Round) growth units we plan to utilize have been developed to improve upon several characteristics relative to gear commonly used on off-bottom farms throughout North America. Most relevant to our farm, from the perspective of other stakeholders, is likely 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 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.
The shape, design, and mobility of BOBR units minimize the shading of sunlight on the eelgrass below the growth units. For overwintering, BOBR units are sunk in a different way than commonly used oyster growth units. Rather than the cage resting on the bottom, BOBR units will remain buoyant and only the lines are sunk. This significantly reduces the contact area relative to other growth units commonly used which mitigates the effect on eelgrass during overwintering. Additionally, BOBR is deployed on two static lines instead of one. This feature along with its low profile significantly reduces risk of storm loss.
Our BOBR oyster aquaculture growth system has been in use since August 2019. It has performed exceptionally well, and we are very pleased with the system. More units will be deployed on our test site this spring and further trials conducted. By the time a decision is reached on our application, more than three years of experience with BOBR will have been gained. BOBR is a growth system that minimizes carbon inputs while improving productivity and product quality.
Scientific studies will commence this spring focused on quantifying the actual environmental impacts, positive and negative, our BOBR growth system imparts. These studies will examine effects on eelgrass, the benthic environment, and water quality. Results of these studies will be used in part to substantiate the benefits of BOBR relative to other growth units commonly used in the industry.
We are excited to have more photos and videos of BOBR in action soon!
Who designed BOBR?
Ernie Porter P. Eng., President of TPO, joined forces with Philip Docker, owner-operator of ShanDaph Oyster Farm and 20 year veteran of the industry, to address deficiencies in technology available to the oyster aquaculture industry. They focused on improving form, function, productivity, and efficiency. Together they formed DockPort, Inc. DockPort is home to BOBR & Oyster-Matic, the machine that enables our BOBR growth system to be mechanized.
The BOBR growth system offers an economical mechanized system to an industry that has to date relied on physical labour for production. This system will reduce potential environmental impacts while drastically increasing farm productivity and improving work conditions for farm staff. BOBR will be manufactured in Nova Scotia and available to oyster farmers worldwide.
BOBR Units vs. Commonly Used Units
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.
For further reading please see the links below to relevant scientific journal articles.