The Hatchery Process
Oysters eat microalgae (single celled plants) by filtering the cells from the water. If the hatchery is the engine that drives the business, microalgae fuel the engine. We have two culture systems, one for growing small cells that are the primary food for the young larvae, and a second, proprietary system for growing the bigger cells we feed to our broodstock, older larvae, and the young juveniles before they leave the hatchery. We are investing in continual improvement of our algae culturing systems through research and development, with the goal of offering microalgae to other hatcheries.
Broodstock & Genetics
We use a variety of broodstock lines, including our own oysters grown in the Damariscotta River that we selectively breed for shape, cup depth, and rapid growth. We also maintain a state-approved broodstock quarantine facility which allows us to safely hold broodstock oysters from out of state. The way to produce disease resistant seed is to use disease resistant broodstock. We only spawn oysters that are believed to be disease resistant, typically from selective breeding. These stocks include disease resistant oysters from the Haskin NEH® line from Rutgers University and the 4DXB line from the Virginia Institute for Marine Science (VIMS) Aquaculture Genetics and Breeding Technology Center.
We produce both diploid (2n) oyster seed which have the normal two sets of chromosomes, as well as triploid (3n) oyster seed with three sets of chromosomes. Triploids have been shown, in some cases, to grow faster than diploids; and because they are sterile, their meat yield and quality tends to be better during the summer months when the diploids are spawning. Our triploid seed is produced naturally from tetraploid (4n) broodstock with four sets of chromosomes that are crossed with diploid (2n) broodstock. Triploid seed is sold under license from VIMS and Rutgers, as well as 4C’s Breeding Technologies, Inc; therefore license fees apply to these seed.
The broodstock oysters are ripened by holding them at elevated temperatures with an ample supply of food for several weeks. Broodstock conditioning typically begins late in the fall, and as the hatchery season progresses we rotate different groups of oysters through the system to ripen and spawn. Please see our seed order form for currently-available genetic crosses.
Ripe oysters are placed in their own basins and stimulated to spawn by rapidly cycling the water temperature. We typically sacrifice some males from the desired genetic line and add stripped sperm to the water in the basins to help initiate spawning. The oysters spew their gametes into the water turning it milky. The females are easy to identify because the eggs have a distinctly granular appearance, and the egg basins are pooled into larger buckets where, if necessary, more sperm is added to insure good fertilization. The fertilized eggs are then washed on a 20 micron screen and placed in calibrated buckets where they are counted and placed into the larval culture tanks. Our first spawn of the season is usually the very beginning of January, and our last is generally late June or early July.
Within 48 hours after fertilization the oyster embryos grow clear shells around themselves and a ciliated appendage which they extend from between the two shell margins for swimming and feeding. The larvae are fed daily and the tanks are drained on special sieves every 48 hours to change the water and grade the larvae on sizing screens. At each drain-down the larvae are restocked at the appropriate density to maintain rapid growth. At 48 hours the larvae are retained on a 50 to 60 micron screen (.0024” to .0029”). By about 14 days the larvae are held on a 200 micron (.0083”) screen and they develop two eyespots that guide them away from the light towards the bottom, and a foot that they use for crawling. They are now ready to undergo a metamorphosis and become a bottom dwelling, non-motile oyster. This process is called setting.
The ready-to-set larvae are placed into shallow, fine-mesh floating screens. A layer of finely ground oyster shell is spread on the screens to provide the substrate for attachment and metamorphosis. Once set, the oysters quickly begin to feed and grow as post-set juveniles, now called seed. After about a week on the setting screens the seed oysters are screened to separate them from the shell chip and are moved to upwellers.
When the seed oysters are big enough they are moved to various upwelling systems. First they are put in passive upwellers where the water is drawn up through a layer of seed using air lifts. The biggest seed is grown in forced upwellers where the culture water is actually pumped up through a more concentrated mass of animals. Upwellers are extremely space efficient and can provide very uniform growing conditions.
All of the seed we sell comes directly from the hatchery. The hatchery seawater is highly filtered and irradiated with ultraviolet light. This high level of water treatment, strict protocols for handling broodstock and fertilized eggs, and regular health certifications allow us to guarantee that the seed we ship is disease free. We sell seed retained on sieve sizes ranging from 1.0 mm to just under 3.0 mm priced per thousand oysters, and shipped FedEx next day.