Hatchery Operations

Algal Culture

The oyster hatchery within the Acuff Aquaculture Center has all of the standard capabilities of any bivalve hatchery. At the heart of these operations is the algal-culture lab, where four strains of unicellular algae are cultured to feed larvae, recently set oyster seed (or spat), and broodstock, the parent animals used for spawning. Algae cultures are raised using batch procedures, so as they continue to grow and increase in density, they are progressively transferred from small flasks to 10-liter carboys to 200-liter kalwall tubes or a hanging bag system. By providing all of the components needed for photosynthesis, this lab creates the perfect conditions for algal cultures to grow continuously year-round. The algal ration for each tank in the hatchery is calculated on a daily basis, and the total volume and proportion of each algal species that they receive is adjusted as the oysters grow and their nutritional needs change.

Brood Stock & Conditioning

The broodstock room in any standard hatchery holds specific stocks of oysters in temperature-controlled tanks. In the spring, the parent oysters stored in these tanks are ‘fooled’ into thinking that it is early spring by increasing the temperature of the water and feeding the oysters large quantities of algae. Over the course of four to eight weeks, these animals develop mature gametes, or eggs and sperm, in preparation for spawning. This process is often referred to as ‘conditioning’ or ‘ripening.’ During mid- to late summer, these same tanks can be used to hold parents that are already sexually mature. At this time of year, the tank temperatures are cooled slightly to prevent the broodstock from releasing gametes before hatchery personnel are ready to use them.

What sets ABC’s hatchery work apart from many others is the large number of genetically distinct spawns produced each season, a process requiring exceptional diligence from hatchery personnel, large amounts of record keeping and labeling, and complete separation of dozens of family and line groups. Acuff’s state-of-the-art broodstock room will allow conditioning of up to 3,500 oysters each Spring, a more than eight-fold increase over the capabilities of the previous oyster hatchery.  

Hatchery Floor

The main hatchery floor is where spawning and larval culture operations are concentrated. This space contains a workbench and over one hundred small larval tanks of two volumes, 60 or 200 liters. The smaller tanks are used for ABC’s family groups and experimental cultures, and the larger tanks are used to produce their line cultures. This setup 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. ABC’s standard operating procedure is, however, the production of many different genetic groups of small volume. From each 200-liter tank, hatchery staff can usually harvest 400,000-600,000 mature larvae, which develop into a sufficient quantity of seed (or spat) for field trials and for holding as parents for the next generation.

Larval Setting & Nursery

Oyster larvae complete their planktonic stage in two to three weeks and are harvested when they become ready to ‘set,’ or metamorphose to a sedentary form. Larvae are encouraged to set on ground oyster shell in shallow downweller screens. Newly set seed oysters continue growing inside the hatchery for ten to fourteen more days before they’re moved outdoors to the nursery system. In the nursery, they are kept in upwelling screens that allow raw river water to pass through. This unfiltered water pumped directly from the river contains microscopic algae and other plankton on which the seed can feed.

Dispersal to the Field

When the seed reach plantable size, generally around 8-10 mm in shell length, they are put into mesh bags or longline baskets and deployed on ABC’s field sites for continual evaluation, testing, and maintenance. In one to two years, these animals will be large enough to spawn with, and the entire cycle will begin again.

Learn more about the role of field sites in ABC's breeding program.