OYSTERS

Oyster culture facility

Raising oysters to help Chesapeake Bay

History

Stephanie Alexander, manager of oyster culture facility, explains the process of growing an oyster from broodstock to deployment.

The Broddus and Margaret Ann Jones Oyster Culture Facility at the University of Maryland Center for Environmental Science's Horn Point Laboratory is one of the largest oyster culture facilities on the East Coast. It produces a variety of oyster larvae for use in oyster research, oyster restoration, and educational projects.

In 1972, Tropical Storm Agnes tore through the region and devastated already vulnerable populations of oysters. Two years later, our researchers began what would become an ongoing effort to restore oysters in Chesapeake Bay.

The researchers quickly outgrew the original facility, eventually moving into the Aquaculture and Restoration Ecology Laboratory in 2003. This newer space is not only larger, but also provides quarantine and controlled environmental facilities.

“Every year since then, we’ve been getting bigger and better,” said Stephanie Alexander, oyster culture facility manager. “We have really nice technology that allows us to do what we’ve never done before. To give you some scale, in 1997 we did about 10 million spat on shell. They were all by hand shell bags. Then we started to get a little more advanced and started to use stainless steel containers, having machinery to do all of the lifting. As of 2016, our best year, we did 1.78 billion spat on shell.”

Oyster Recovery Partnership

In 1993, Donald “Mutt” Meritt joined an oyster roundtable called together to address concerns about the low population and devise possible solutions. A year later, the Oyster Recovery Partnership was established, and with it came an action plan for how the Horn Point oyster culture facility and its partners could begin to rebuild the populations lost over time. Learn more about the partnership and its successes.

How to raise an oyster

The culture facility encompasses a series of systems, each with its own special purpose to allow staff to control aspects of the oyster’s life cycle and to produce large numbers of oysters for use in the partnership’s programs.

An oyster’s life starts the same in the culture facility as in the wild. Once fertilized, an egg will drift with the water until it develops into a larva. These larvae will live in the water column for the next two to four weeks, swimming in the currents to find food while they mature.

At about the two-week mark, the larvae enter the pediveliger stage. Using an appendage they grow called a foot, the larvae will begin to move around in search of a hard surface (like an oyster shell) to attach themselves using a glue that they secrete. At this point, the larvae undergo complete metamorphosis of internal anatomy and become what is called a spat.

In the oyster culture facility, larvae are kept in 12- by 12-foot tanks in their initial weeks.

The staff drains its tanks twice a week to keep them clean and regularly filters the water to keep copepods, larval worms, and other organisms that the hatchery doesn’t want to grow from making a home in the tanks. Larvae are retained on a screen as the water pours through. Once empty, staff will scrub the tank, refill it, and return the larvae.

The larvae are fed a specially made batch of algae while they grow in the tanks.

The setting process

Near the oyster culture facility at Horn Point Laboratory is a yard filled with piles of oyster shell. Here the Oyster Recovery Partnership, with help from the Maryland Department of Natural Resources, amasses tons of shell that will eventually serve as new homes for the larvae Meritt and his team grow.

Before the shell is ready, however, it must be stored for a year to make sure organic matter rots off the shell. Then the shell is run through a washer and grater before it is divided into several tall but narrow stainless steel cages. The cages ease transport of large volumes of shell from the shell yard to large water tanks on the Horn Point pier on the Choptank River. The Oyster Recovery Partnership puts the cages in the tanks, and the hatchery fills the tanks with water. Then the larvae go in.

The water in the tank is static when the larvae go in, but once they’ve had enough time to attach themselves to a shell and go through metamorphosis, culture facility staff activate a pump with river water, which will bring in food for the spat.

The spat typically remain in the setting tanks for a few days before they are deployed to a grow-out site in the Chesapeake Bay. The culture facility signals to the partnership when a tank is ready, and they will load those tanks—usually about 10 per day—to a vessel that will ship them out to a predetermined spot that has been deemed suitable. One tank could yield between a half million and 1.5 million oysters.

The partnership will then clean the tank, reload it with cages of clean shell, and the process starts over with new larvae.