Marine Life Center

State-of-the-Art Marine Hatchery for Oysters

A high priority for the Gulf Coast Marine Life Center is the development of infrastructure for and production of shellfish seed for enhancement and restoration. The GCMLC plans to produce two bivalve mollusc species, the Eastern oyster (Crassostrea virginica) and the bay scallop (Argopecten irradians), with an initial focus on oysters.

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Gulf Coast Marine Life Center staff and University partners from the University of New Hampshire have extensive experience in all stages of large and complex oyster production, from hatchery to final grow-out in both private aquaculture and restoration. The Center envisions that the current partners from UNH will oversee the purchase and installation and initial operation of the hatchery and provide training to the local labor pool for continued operation. They will also participate in restoration planning and implementation in conjunction with local and regional partners and provide training and advice for entrepreneurs interested in private aquaculture.

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Oysters
Courtesy University of New Hampshire

The initial phase of oyster production is broodstock conditioning, followed by induced spawning, larval culture, setting, and nursery culture. To condition broodstock, adult oysters are fed an algal diet high in lipids and held at appropriate temperatures to insure optimal gonadal development. Thermal shock is then used to induce spawning and fertilization, this takes place in the water column. Fertilized eggs develop and progress through a series of free-swimming larval stages over a period of 14 to 20 days, depending on water temperature. These stages are referred to as the trochophore, veliger and pediveliger. The trochophore larvae feed on very small algae as they move through the water column. Trochophore larvae quickly develop into more motile veliger larvae. Toward the end of the larval cycle, pediveligers develop a foot that helps them find a suitable hard substrate on which to attach (set) and transform into small oysters. This stage is also called an “eyed larva” because of the development of a pigmented eyespot.

The setting stage can be amended depending the intended use of the seed. For restoration, stock enhancement or living shoreline purposes, the eyed larvae are set on oyster shell or some other hard substrate in large setting tanks. This method produces clusters of oysters, similar to what is found in natural beds and reefs. Once the larvae have set (24-48 hours) they are held in the tanks with flow through ambient seawater before being transported to the desired field location. Eyed oyster larvae can also be shipped dry to other locations for setting. This method, known as remote setting, greatly reduces transportation costs and results in higher survival of the larvae and seed.

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Oyster Larvae
Courtesy University of New Hampshire

The Gulf Coast Marine Life Center recognizes that the distinct phases of oyster production rely on high volume production of pure cultures of microalgae. The technology for algal production is well developed, and the Gulf Coast Marine Life Center hatchery will incorporate a state of the art continuous production system such as the Seasalter SeaCAPS, which will provide a continuous supply of algae without down time to re-clean containers and introduce new cultures.

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The Gulf Coast Marine Life Center's land-based facility will have 5,000 sqft. dedicated for the hatchery and nursery stages of oyster production. Based on projected production capacity of the facility, the GCMLC oyster team is planning on ten oyster production runs of 22.5 million eyed larvae per run, for a total of 225 million eyed larvae per year, using a conservative survival rate of 60%, the Center could produce annually 135,000,000 spat. Using a restoration calculation survival rate for spat on shell of 15%, an estimated 20,250,000 oysters would survive. The oysters produced will be made available for stock enhancement, habitat restoration, and shoreline stabilization.