![oyster spat shell oyster spat shell](https://media.fisheries.noaa.gov/dam-migration/oyster_spat.jpg)
For example, generations of Chesapeake watermen have harvested wild oysters from grounds scattered around the Bay. However, restoring self-sustaining populations of wild oysters to a significant level may prove difficult because of a host of ecological, economic, and cultural hurdles. And oyster reefs provide habitats for a variety of other fish, benefitting the entire ecosystem. That is because of the creatures’ ability to filter vast amounts of water, improving its quality. Increasing the Chesapeake’s oyster populations is a high priority in Maryland. We offer assistance and information to prospective oyster producers, business owners, commercial harvesters, resource managers, students, and educators. Offer technical advice about aquaculture methods, business financing, and public policy.Provide seed for oyster aquaculture and restoration of wild oysters.Maryland Sea Grant Extension is working with its many partners to bring oysters back-by using aquaculture to cultivate the mollusk for food and restoration. On the Bay: Chesapeake Quarterly's Blogįind out more about this two-year study comparing contained culture equipment for oyster aquaculture production.ĭisease, habitat loss, overharvesting, and poor water quality have left the Chesapeake Bay’s iconic wild oysters in a dismal state, at just 0.3 percent of their teeming population in the early 1800s, according to a 2011 research study by the University of Maryland Center for Environmental Science.Fellowship Experiences: A Students' Blog.Depending on their intended use, they spend several weeks to several months in the nursery system before being moved as "seed oysters" to grow-out or restoration areas. Juvenile oysters are regularly sorted by size, counted, and re-distributed in the upweller nursery to optimize growth and survival. After about two weeks, they are moved to "upwellers" in raw seawater and feed on whatever food is naturally available. Newly-metamorphosed oysters are barely visible to the naked eye and are raised in filtered seawater in "downwellers," where they are fed cultured algae and grown to a more manageable size. At the AIC, the larvae metamorphose without attaching ("cultchless"), yielding individual oysters ("singles") that are ideal for the half-shell market. In nature, larvae attach to a solid surface such as an adult oyster shell. Juvenile oysters ("spat")Īfter about two weeks, larvae are ready to metamorphose, or change, into "spat", or juvenile oysters. The water is drained through filter screens that retain the larvae, which are observed for condition, counted, and measured, before being returned to the larval tanks with food and clean water. Larvae at the AIC are raised in filtered, sterilized seawater so microalgae must be added daily as food. Two days after fertilization, oyster larvae already have shells. Larvae are microscopic and free-swimming. The gametes from male and female broodstock are mixed together to allow fertilization of the eggs.įertilized eggs become oyster larvae. A single adult female oyster can produce many millions of eggs in a season. The gametes (eggs and sperm) from ripe broodstock are either released naturally by the oysters or removed surgically. In the Delaware Bay, natural oyster populations tend to reproduce in late June or early July.Īt the AIC, broodstock oysters are moved into temperature-controlled tanks in January, given plenty of food (also produced at the AIC) and are ready to reproduce by late February. The "Rutgers oyster" is fast-growing and disease resistant. At the AIC, most broodstock are a strain of the Eastern oyster ( Crassostrea virginica) developed at Rutgers University. Broodstockīroodstock are adult oysters (2–3 years old) used to make baby oysters. After a few weeks or months, the spat are considered seed oysters. Fertilized eggs become microscopic oyster larvae, which swim freely for about two weeks before metamorphosing, or changing, into oyster "spat," or juvenile oysters. Oyster seed production starts with parent oysters, or broodstock, which provide gametes (eggs and sperm). They can also be used to restore natural oyster populations or natural ecosystems, and for research. Seed oysters are small oysters, about 2–25 mm long, provided primarily to oyster growers for the half-shell market.