The heart of the oyster-breeding effort at VIMS' Gloucester Point campus is the oyster hatchery run by the Aquaculture Genetics and Breeding Technology Center (ABC). The hatchery has served as VIMS' principal oyster-breeding facility since the inception of ABC in 1997. Since the 1998 spawning season, ABC researchers have continually refurbished and redefined the operating procedures of the hatchery to better reflect its role in shellfish genetics and oyster breeding.
The Gloucester Point hatchery has all the capabilities of any modern bivalve hatchery. At the heart of these operations are the algal-culture facilities where specific strains of unicellular algae are cultured to feed larvae, young spat (recently set oysters), and brood stock (parents for the spawnings). Algae are raised in batch culture, which means that they are progressively transferred from test tubes to 2-liter beakers to 20-liter carboys to 100 to 200-liter kalwall tubes. Some cultures are transferred to 2,000 liter tanks.
What sets the Gloucester Point hatchery apart from any other is the large number of genetically distinct spawns produced each season, a process requiring exceptional diligence from hatchery personnel. A brood-stock room holds specific stocks of oysters in temperature-controlled tanks. The water is filtered and food is provided by the batches of algae cultured constantly. In the Spring, the principal function of the brood stock room is to "fool" parent oysters into thinking that it is early spring, and thereby cause them to start maturing sexually, eventually (in 4-8 weeks) leading to mature eggs and sperm. This is done by controlling the temperature of the water and feeding the oysters large quantities of algae. During mid- to late summer, the brood stock room is used principally to hold parents that are already sexually mature. At this time of year the temperatures that were used to stimulate reproduction (about 22°C) are sufficiently cool to prevent the parents from releasing gametes before hatchery personnel are ready to use them.
The "working" part of the hatchery is the hatchery floor. This is covered by dozens of small white larval tanks, each about 200 L in volume. On occasion, small experiments are done in 15-liter "buckets" and larger cultures are accomplished in 1,000- to 2,000-liter tanks. This procedure differs from commercial hatcheries because of the size and number of larval tanks. In commercial hatcheries, a small number of extremely large tanks typically fill the hatchery floor. Our modus operandi, however, is the production of many different genetic groups of small volume. From each 200-liter culture we can easily harvest between 10,000 and 100,000 spat under most circumstances, which is a sufficient quantity for field trials or for holding as parents for the next generation. Our operating procedures are similar to other experimental bivalve hatcheries such as those of the Cape Shore Breeding Station at Rutgers' Haskin Shellfish Research Lab, and the culture facilities at the University of Maine's I.C. Darling Center.
Oyster larvae pass through their planktonic stage in the hatchery and are "harvested" when they become ready to "set" (metamorphose to a sedentary existence). We manage the setting process in a number of ways depending on the type of evaluation scheduled for the "seed" oysters. After the hatchery, they are kept in an upweller system that contains the seed oysters as discreet genetic entities in containers that allow raw water to pass through them. Raw water pumped directly from the York River contains microscopic algae and other plankton on which the seed can dine.
Dispersal to the Field
When the seed reach plantable size, generally around 8-10 mm, they are parsed out to various field sites for evaluation, testing, or maintenance until they are large enough to breed again.