most Virginia aquaculture operations involve raising oysters in cages, where predation can be controlled easier than placing oysters on a reef
Source: Virginia Institute of Marine Science, Aquaculture Genetics and Breeding Technology's Oyster Breeding Program Manual
The starting requirement of the aquaculture-based oyster growing business is to maintain adult oysters in a hatchery that spawn. They generate oyster larvae that will later attach to old oyster shells or other hard material underwater. The Virginia Institute of Marine Science (VIMS) established a hatchery at Gloucester Point and spawned its first oysters in 1998.
In 2016, the Aquaculture Genetics and Breeding Technology Center at VIMS was:1
VIMS developed the procedures to maintain adult brood-stock, to choose when they spawn by altering temperature and the amount of algae provided as food, and to manage the oysters through their planktonic stage until they settle on a hard surface (becoming "spat") and begin to grow into adult oysters. It takes two years for VIMS to grow oysters before they are sold.
The VIMS hatchery at Gloucester Point develops and maintains different genetic strains of native Crassostrea virginica oysters today, selling sperm from tetraploid males plus eggs from disease-resistant diploid females to commercial hatcheries. The hatcheries fertilize the eggs and grow triploid spat, which are sold to aquaculture operations in the Chesapeake Bay and on the Atlantic Ocean coastline.
VIMS grows its tetraploid males and diploid females by feeding the initial larvae with unicellular algae raised in specialized tanks at Gloucester Point. After passing through the planktonic stage in the hatchery, the larvae metamorphose to a sedentary existence when they "set" on a hard surface. After they set, VIMS moves the seed oysters to upweller systems and pumps York River water through the tanks to provide food. When "seed" oysters reach 8-10mm in size, VIMS moves them again to grow-out farms until the oysters mature into adults ready to breed.
VIMS produces brood stock adapted to different aquatic environments, both in the Chesapeake Bay and on the Atlantic Ocean. The DNA in the cells of the oysters has been modified through a breeding program based on classical modification of traits through repeated selection of high-performing individuals; VIMS has not inserted genes through the genetic modification (GMO) techniques used to create herbicide-resistant corn. The process to create tetraploid oysters was developed at Rutgers University in 1993, and through intellectual property laws Rutgers earns money from the use of its techniques.
Chincoteague Bay, with high-salinity of 28-35 parts per thousand (ppt) of salt, has been used as a test site for selecting the best-performing oysters for subsequent breeding. A test farm located on the Lynnhaven River allows testing in a moderate salinity (17-25 ppt) site. A low-salinity (8-15 ppt) test farm is on the Yeocomico River. A test farm on the York River is located where salinity is moderate and the disease challenge is high.
The Kauffman Aquaculture Center on Locklies Creek, a tributary of the Rappahannock River, was built in 2005 to expand the capacity of VIMS to conduct oyster research and breeding.
Commercial hatcheries buy adult tetraploid males and diploid females and manage their spawning to produce triploid spat, with three sets of chromosomes. The triploid spat sold to aquaculture companies and individuals for commercial harvest are sterile, so a hatchery's customer can not by a batch of oysters just once and subsequently breed their own triploid oysters.
most oysters grown commercially in the Chesapeake Bay start as larvae in a hatchery at the end of Callis Wharf Road on Gwynns Island
Map Source: ESRI, ArcGIS Online
VIMS created different strains by crossbreeding disease-resistant oysters from Louisiana and the Delaware Bay, then from five Virginia rivers (Rappahannock River, Great Wicomico River, Mobjack Bay, York River, and James River). Five are sold now: low-salinity Lola (acknowledging the Dermo-resistant oysters imported from the Gulf of Mexico), high-salinity hANA, high-salinity and low-salinity versions of DEBY (acknowledging the MSX-resistant oysters imported from the Delaware Bay), and XB (or CROSBreed).2
The largest commercial hatchery in the bay is Oyster Seed Holdings on Gwynn Island in Mathews County. It started in 2008 and quickly grew to become the dominant supplier. The brood stock manager, a woman known locally as "Oystermama," added some fun to the job by selecting different types of music to play in the spawning laboratory, finishing the spawning season with Marvin Gaye's "Let's Get it On."3
the Virginia Marine Resources Commission uses the Oyster Aquaculture Suitability Model to identify locations most suitable for cultivating oysters in Virginia water, to minimize conflicts with crabbing, clamming, fishing, swimming, recreational boating, and submerged aquatic vegetation (SAV) growth
Source: Virginia Coastal Zone Management Program, Virginia Coastal Geospatial and Educational Mapping System (GEMS)
The tiny "spat" produced at a hatchery are then placed in wire or PVC-pipe cages and placed in the waters where they will grow. Some oysters are raised initially at one location, then moved to acquire a unique taste in waters of a specific salinity and mineral composition.
The cages are suspended above the bottom of the river, Chesapeake Bay, or Atlantic Ocean to minimize problems with silt, which might coat the shells and suffocate the young oysters. The cages are brought to the surface at times, and oysters can be placed in a tumbler to ensure they grow in the most-marketable shape. In about 18 months, oysters are collected and sold, before they can be affected by disease.
Source: Nature Conservancy, Aquaculture By Design
One reason for the boom is a new, genetically-modified variant of the Eastern oyster (Crassostrea virginica). It was created in response to proposals to import an Asian species that was expected to be more resistant to the bay's pollution and diseases. First the Japanese oyster (Crassostrea gigas) was tested, but customers rejected its taste. The focus then became the Chinese oyster (Crassostrea ariakensis).4
Only a sterile version of the Asian species was considered for introduction to the Chesapeake Bay, since sterile Asian oysters could not start reproducing naturally and create unexpected consequences for the bay's ecology.
VIMS scientists originally developed a sterile "triploid" version of the native Crassostrea virginica species for comparison to the sterile version of the Asian species. The triploid oysters did not spend energy in reproduction, and in an unexpected development VIMS discovered that the triploid version of the native species grew to maturity before diseases could affect them.
The alternatives analysis required to complete the Environmental Impact Statement before introducing Asian oysters revealed that sterile native oysters could be used, without the risks of introducing a non-native species. In April, 2009, the Corps of Engineers concurred with Virginia and Maryland officials and recommended against introducing Crassostrea ariakensis to the Chesapeake Bay.5
oyster farms grow their crop in cages suspended in the water, rather than scatter oysters on reefs
Source: Virginia Sea Grant, Cherrystone Aqua-Farms
Commercial production of native oysters now relies upon the fast-growing triploid version of Crassostrea virginica. Since no energy is dedicated to producing eggs or sperm, the sterile oysters grow to harvestable size before Dermo or MSX kill them in their third year. Because triploids have no spawning season, the oysters are plump during the summer months (May-August) as well as the traditional harvest time of months with an "R" in their name (September-April).6
Since the state owns submerged lands, the Virginia Marine Resources Commission (VMRC) issues permits for raising oysters in cages suspended above the bottom.
Holders of a lease for submerged lands do not need a permit for raising oysters the traditional way, by planting seed oysters and adding shell, or if the cover the beds with structures (such as a net) that are no more than 12 inches high. Leaseholders and everyone else must get a VMRC permit if they will use cages that extend more than 12 inches above the bottom, such as floating cages.7
number of oysters planted by Virginia aquaculturists
Source: Virginia Institute of Marine Science, Virginia Shellfish Aquaculture Situation and Outlook Report - Results of 2010 Virginia Shellfish Aquaculture Crop Reporting Survey
Defining where oyster aquaculture is appropriate along the shoreline also involves local governments, which have zoning authority over land uses. In some areas, neighbors fear small operations with just a few cages attached to existing docks ("oyster gardens") will grow into industrial operations with expanded waterfront infrastructure.
The 2011 General Assembly rejected a proposal to modify the definitions in the Virginia Right to Farm Act, which would have blocked local government from controlling aquaculture operations. The 2011 General Assembly also considered a bill to establish 15 Aquaculture Opportunity Zones on 1,000 acres of bay bottom, much of it away from the shoreline. Opposition from existing oyster farmers concerned about oversupply in the market helped cause the bill to be rejected, but smaller operations feared a few operators would gain control over most aquaculture opportunities.
The number of oyster farms in Virginia grew from 60 in 2013 to 134 in 2018, an increase of over 120%.8
VIMS uses test sites in areas of high, medium, and low salinity to developed different strains of oysters adapted to local conditions
Source: Virginia Institute of Marine Science, Aquaculture Genetics and Breeding Technology's Oyster Breeding Program Manual
In 2018, the Virginia Marine Resources Commission approved an oyster lease for 700 floating oyster cages in Mathews County. A group of local landowners opposed the lease, concerned that the scenic vista of the Mathews Haven cove on Gwynns Island would be converted into an ugly waterfront. Opponents also emphasized that the cages would affect public uses of the 5.5 acres of public waters, preventing use of the area outside of the shipping channel by jet skies, paddleboards, kayaks, and other recreational watercraft.
Aquaculture advocates highlighted the economic benefits of the project, including the jobs provided for watermen. In the end, the Virginia Marine Resources Commission approved the lease on a 4-2 vote, with two members abstaining. The majority determined that authorizing more oyster cages would provide a greater "public good" than leaving the site undeveloped.9
the Virginia Marine Resources Commission approved a lease in Milford Haven in 2018, over strong objections from property owners on the waterfront
Map Source: ESRI, ArcGIS Online
areas proposed for Aquaculture Opportunity Zones in Mathews County
Source: Middle Peninsula Planning District Commission, Shellfish Aquaculture and Working Waterfront Infrastructure: Mathews County Phase II
A proposal for cages with 2,100 floating modules at Seashore State Park at the 64th Street boat ramp was rejected by the Virginia Marine Resources Commission (VMRC) in 2022. The Lynnhaven Oyster Company's project generated over 1,o00 public comments, both in support of oyster aquaculture and in opposition to the impacts on navigation and the scenic view. Staff recommended approval of 1,800 floating modules.
An artist's depiction of the floating modules near the boat ramp evidently affected the decision. The final vote by the members of the Virginia Marine Resources Commission was 4-2 against issuing a state lease for the use of the water above the state-owned bottom of Broad Bay.10
a proposal for 2,100 floating modules next to the Seashore State Park 64th Street boat ramp was rejected by the Virginia Marine Resources Commission in 2022
Source: ESRI, ArcGIS Online
a visual image of 2,100 floating cages next to the Seashore State Park 64th Street boat ramp was a key piece of evidence before the vote
Source: Virginia Marine Resources Commission (VMRC), 2022-08-23 Commission Meeting (3:30 in recording)
By 2023, a mysterious problem was killing about 1/3 of the triploid oysters just as they reached market size. Unexplained die-offs had been reported as early as 2012, and were not associated with normal causes of mortality such as diseases, toxic algae blooms, quick drops in dissolved oxygen, and too much/not enough salt in the water. Aquaculture specialists suspected a genetic variance had been introduced into the brood stock and some environmental factor was beginning to trip genetic switches.
The president of one oyster farm affected by the die-off, Big Island Aquaculture on the York River, said simply:11
In 2022, 64% of the oysters harvested in Virginia came from aquaculture operations. In contrast, only 13% of Maryland oysters were farm products.12
In 2022-23, 300,000 bushels were harvested from public rocks and 400,000 bushels were produced by over 200 private aquaculture operations. That was the highest harvest in 35 years, and was achieved in part because the Virginia Marine Resources Commission extended the public harvest season by two weeks.13
Sudden Unusual Mortality Syndrome (SUMS) is a threat to oyster farmers. For unknown reasons, up to 50% of the triploid oysters in cages may die before they reach the harvest stage. No pathogen has been identified. The problem does not appear to be associated directly with an algae bloom, disease, parasites, drops in water salinity, or any other single factor.
Natural oyster beds are not impacted a heavily. "Sudden" is included in the name of the problem because aquaculture farmers discover that the meat of their oysters disappears quickly in the second year, soon before they are ready to harvest.
Researchers met in 2024 to determine the best approach to defining and solving the problem. They concluded that Sudden Unusual Mortality Syndrome (SUMS) was triggered by complex interactions between multiple factors:14
the percentage of oysters harvested from private aquaculture operations has climbed steadily since 2004-2005
Source: Virginia Marine Resources Commission, Shellfish Management Division Evaluation, 08/22/2023 (Graph 1)
aquaculture - growing oysters in floats, Taskinas Creek (Chesapeake Bay Virginia National Estuarine Research Reserve)
Source: National Oceanic & Atmospheric Administration (NOAA)
1. "Hatchery to Harvest: Virginia's oyster aquaculture begins with ABC," Newport News Daily Press, June 5, 2016, http://www.dailypress.com/news/science/dp-nws-oyster-breeding-vims-20160612-story.html (last checked June 7, 2016)
2. "Hatchery to Harvest: Virginia's oyster aquaculture begins with ABC," Newport News Daily Press, June 5, 2016, http://www.dailypress.com/news/science/dp-nws-oyster-breeding-vims-20160612-story.html; "Facilities & Equipment," Virginia Institute of Marine Science, http://www.vims.edu/research/units/centerspartners/abc/facilities/index.php; "Oyster Hatchery," Virginia Institute of Marine Science, http://www.vims.edu/research/units/centerspartners/abc/facilities/glo_pt_hatchery/index.php; "The Aquaculture Genetics
and Breeding Technology's Oyster Breeding Program," Virginia Institute of Marine Science, 2009, p.2, p.6, p.24, http://www.vims.edu/research/units/centerspartners/abc_migrate/_docs/oyster_breeding_program.pdf (last checked June 7, 2016)
3."Oyster Hatchery," Virginia Institute of Marine Science, http://www.vims.edu/research/units/centerspartners/abc/facilities/glo_pt_hatchery/index.php; "Seeds of Success," Bay Journal, October 15, 2013, http://www.bayjournal.com/article/seeds_of_success; "Crop of the Bay: Homegrown Oysters," Middlesex County Southside Sentinel, October 30, 2012, http://www.ssentinel.com/index.php/rivah/article/crop_of_the_bay_homegrown_oysters (last checked November 7, 2014)
4. "Trials & Errors & Triploids - Odyssey of an Oyster Inventor," Chesapeake Quarterly, June 2010, http://ww2.mdsg.umd.edu/CQ/v09n2/main2/ (last checked July 7, 2014)
5. "Officials Rule Against Introducing Asian Oysters into Bay," Chesapeake Bay Program, April 1, 2009, http://www.chesapeakebay.net/blog/post/officials_rule_against_introducing_asian_oysters_into_bay (last checked July 7, 2014)
6. "The Aquaculture Genetics and Breeding Technology's Oyster Breeding Program," Virginia Institute of Marine Science, 2009, p.8, http://www.vims.edu/research/units/centerspartners/abc_migrate/_docs/oyster_breeding_program.pdf (last checked June 7, 2016)
7. "Shellfish Aquaculture, Farming and Gardening," Virginia Marine Resources Commission, http://www.mrc.virginia.gov/Shellfish_Aquaculture.shtm (last checked July 8, 2014)
8. "Virginia oyster industry fights off aquaculture bills," Daily News, April 4, 2011, v; "Table 19. Mollusk Sales by Species: 2018 and 2013," 2017 Census of Agriculture, US Department of Agriculture, https://www.nass.usda.gov/Publications/AgCensus/2017/Online_Resources/Aquaculture/aqua_1_0019_0019.pdf (last checked January 9, 2024)
9. "'Save The Haven' movement grows in opposition to proposal," Gloucester-Mathews Gazette-Journal, May 30, 2018, http://www.gazettejournal.net/index.php/news/mobilenewsarticle/save_the_haven_movement_grows_in_opposition_to_proposal; "VMRC approves Milford Haven oyster cage proposal," Gloucester-Mathews Gazette-Journal, September 26, 2018, https://www.gazettejournal.net/index.php/news/news_article/vmrc_approves_milford_haven_oyster_cage_proposal (last checked September 29, 2018)
10. "VMRC denies permit for floating oyster cages," WAVY, August 23, 2022, https://www.wavy.com/news/local-news/virginia-beach/vmrc-denies-permit-for-floating-oyster-cages/ (last checked August 24, 2022)>br>
11. "Study seeks to get to bottom of mysterious die-offs at Chesapeake Bay oyster farms," The Virginian-Pilot, September 2, 2023, https://www.pilotonline.com/2023/09/02/study-seeks-to-get-to-bottom-of-mysterious-die-offs-at-oyster-farms/ (last checked September 6, 2023)
12. "Fisheries in Flux," Save the Bay, Chesapeake Bay Foundation, Fall 2023, p.15, https://online.fliphtml5.com/jcezj/fbar/#p=17 (last checked November 6, 2023)
13. "Virginia oyster harvest hits milestone," Virginia Public Media, January 8, 2024, https://www.vpm.org/news/2024-01-08/virginia-oyster-harvest-hits-milestone (last checked January 9, 2024)
14. "Oyster farms in Virginia and beyond are suffering unexplained mass die-offs," WHRO, July 3, 2024, https://www.whro.org/environment/2024-07-03/oyster-farms-in-virginia-and-beyond-are-suffering-unexplained-mass-die-offs; "Sudden Unusual Mortality Syndrome (SUMS) In Oysters: Workshop Report," Virginia Institute of Marine Science (VIMS), January 22-23, 2024, https://www.vims.edu/research/topics/_docs/sums-workshop-report.pdf; "Why are so many farmed oysters dying? Scientists mystified," The Virginian-Pilot, September 29, 2024, https://www.pilotonline.com/2024/09/29/why-are-so-many-farmed-oysters-dying-scientists-mystified/ (last checked September 30, 2024)
harvesting oysters used to require a boat and tongs/dredge, but raising oysters in cages now allows harvesting directly from docks attached to the shore
Source: Virginia Institute of Marine Science, Aquaculture Genetics and Breeding Technology's Oyster Breeding Program Manual