Maryland biologists, including Mitch Tarnowski (center), who leads the survey, count the spat, or juvenile oysters, in samples of dredged material as part of the annual fall oyster survey. Photo by Joe Zimmermann/DNR
Governor Wes Moore today announced a historic year for oyster reproduction in Maryland waters. According to the Maryland Department of Natural Resources, the concentration of new oysters in 2025 was nearly six times higher than the long-term spatset average and the second highest ever recorded in the 41-year modern history of the state’s annual fall oyster survey.
“Oysters are the bedrock of the ecosystem in the Chesapeake Bay and provide economic opportunities for communities throughout the state,” said Gov. Moore. “Maryland is now seeing the best news for our oysters in decades; our robust and growing oyster population will help make sure we pass our Bay along to future generations as an heirloom—both as an economic driver for our seafood industry and for the environmental health of our waterways.”
The survey results are a milestone in the recovery of the Chesapeake Bay’s oysters, which are crucial to the health of the Bay and an important economic resource. Preliminary results indicate that the Maryland oyster population is growing throughout state waters at levels not seen in decades, while rates of mortality and disease remain low.
Major survey highlights include:
- At an index average of 250 spat (or juvenile oysters) per bushel at the key sites where scientists measure the intensity of spat, the survey measured reproductive success and potential population growth for oysters at the highest level recorded since 1997—more than three times higher than the prolific reproduction in 2023. The long-term spatset average is 42.2 spat per bushel.
- The survey found the second highest distribution of spat on record since 1985, lower only than 1991. Several areas saw especially high spatsets, including 3,600 spat per bushel on two bars in Broad Creek and more than 2,100 spat per bushel in the St. Marys River restoration sanctuary.
- Oyster mortality levels were the third lowest since 1985, continuing a dramatic decline in mortalities driven by low levels of oyster diseases. In 2025, presence and intensity of the disease Dermo were among the lowest in 36 years. Preliminary results also show very low prevalences of MSX, the other prominent oyster disease in the Bay.
- Maryland Department of Natural Resources shellfish biologists calculate that oyster biomass—the overall estimated weight of oysters in the local ecosystem—is at the highest in the 33 years since the department began estimating that value. Current biomass is more than five times higher than the lowest point in 2002, when oyster populations were devastated by disease.
- Available oyster habitat was also at the highest level, with the three-year average from 2025 tied with the highest in the 21 years the Maryland Department of Natural Resources has measured available hard-surface habitat.
Maryland biologists measure the concentration of young oysters at key monitoring sites annually. In 2025, they found the second highest concentration of oysters at these sites in the history of the modern survey.
“This has been an exceptional year for the oysters of the Chesapeake Bay,” said Maryland Department of Natural Resources Secretary Josh Kurtz. “In the past year, we learned that the state’s oyster populations have tripled in two decades and we also wrapped up major projects at our oyster restoration sanctuaries. Now we’re finding that oysters are reproducing at levels we haven’t seen in nearly 30 years. For an important species that’s struggled for many decades, these are great signs of recovery.”
Gov. Wes Moore, Lt. Gov. Aruna Miller, cabinet secretaries, and environmental leaders add thousands of spat, or juvenile oysters, to a setting tank with recycled oyster shells at UMCES’ Horn Point Laboratory in Cambridge in July 2023. The shells set with spat were later added to oyster restoration sites in the Chesapeake Bay. Credit: Joseph Andrucyk/ Maryland
A key driver for the state’s fishing industry, oysters are second only to crabbing in dockside value. Oyster harvesting has brought in an average of more than $18 million annually over the past five years, when watermen brought in an average of 475,000 bushels annually from 2021 to 2025.
The Maryland Department of Natural Resources and the University of Maryland Center for Environmental Science found that Maryland oyster populations had more than tripled since 2005, to more than 7.6 billion adult oysters as of 2023. In August, Gov. Moore announced that Maryland had completed initial restoration for the ambitious project to bring back oyster populations and habitats in five rivers by 2025.
“The continued strong reproduction and low mortality rates are great news for Maryland’s oyster population,” said University of Maryland Center for Environmental Science President Fernando Miralles-Wilhelm. “This continues the trend seen over the last 20 years and should fuel future increases in the number of oysters.”
The favorable fall survey results also come at a volatile time for the Chesapeake Bay oyster market. The past winter, market conditions, weather, and other factors led to market declines at the start of the 2025-2026 season. Frozen waterways also kept oyster boats from harvesting for stretches of the winter, and the commercial oyster industry has seen declines in market demand. To help watermen make up for lost harvesting opportunities, the Maryland Department of Natural Resources has extended this year’s commercial harvest season for two weeks. In February, the governor also requested a federal disaster declaration for the oyster fishery to help boost the long-term sustainability of the industry.
The Maryland Department of Natural Resources—together with the Maryland Department of Health and the Maryland Department of the Environment—oversee the safety and integrity of commercial shellfish production and use stringent national criteria under the National Shellfish Sanitation Program to evaluate the growing waters for commercial shellfish harvesting.
Oysters spawn in the summer, and their larvae move freely in the water before attaching to a hard surface—often other oyster shells—where they will grow and spend the rest of their lives. Every fall, Maryland Department of Natural Resources scientists dredge hundreds of sites and count the spat growing on oyster shells, rocks, or other materials.
The distribution of spat, or juvenile oysters, throughout the bay, with red representing the highest concentrations. Spat was found north of the Bay Bridge, and especially strong spatsets were found across the Eastern Shore and in sites on the western shores of the Bay.
“These results show what’s possible when Maryland sustains its commitment to oyster restoration and responsible fishery management,” said Oyster Recovery Partnership Executive Director Ward Slacum. “Following the milestone of completing restoration in five Chesapeake tributaries, it’s encouraging to see such strong reproduction across the Bay. ORP is proud to work alongside the state and our partners, and we remain committed to building on this momentum to strengthen oyster reefs, support the seafood industry, and restore the health of the Chesapeake Bay.”
It typically takes about one to three years for an oyster spat to grow into an adult oyster. A mature oyster filters gallons of water daily, helping clean and clarify the water by consuming algae. Oysters build large reefs that are essential habitat for fish, crustaceans, and other marine life.
Maryland agencies have conducted dredge surveys of oyster reefs annually since 1939, in one of the longest-running programs of its kind in the world. The current iteration of the survey has been standardized since 1985.
The Maryland Department of Natural Resources will present the preliminary results of the fall survey report to the Oyster Advisory Commission this evening. The full survey report and results will later be posted on DNR’s fall oyster survey website.
Dots of spat, or juvenile oysters, are visible on an oyster shell taken from a holding tank at Horn Point Hatchery. Taken to restoration sanctuaries, these spat become the next generation of oysters. Photo by Joe Zimmermann/DNR
