Chesapeake Bay’s oysters make a steady comeback
For the fifth year in a row, the oyster population in the Chesapeake Bay is doing well after decades of combating drought, disease, loss of habitat and overharvesting.The Maryland Department of Natural Resources said in March that its annual fall oyster survey showed that the “spatfall intensity index” — a measure of how well oysters reproduced and their potential population growth — again hit above a 40-year median.“We seem to be making some headway,” said Lynn Waller Fegley, director of fishing and boating services for the Maryland Department of Natural Resources. “With the work we’ve done to help restore oysters, and combined with the fact that we’ve been gifted with some really favorable environmental conditions, we’ve seen the oyster population trend upward.”Oyster-processing companies, oystermen, conservation groups and local fish and wildlife departments in the region have spent years trying to boost the population of oysters, which serve an important role as “filter feeders,” sifting sediment and pollutants such as nitrogen out of the water.The cleaner water in turn spurs underwater grasses to grow, while oyster reefs create habitats for fish, crabs and dozens of other species. Adult oysters can filter up to two gallons of water per hour, making them the bay’s “most effective water filtration system,” according to experts at the Chesapeake Bay Foundation, a nonprofit organization that advocates for the health of the bay.Oysters thrive in brackish water — a mix of saltwater and freshwater. They attach and grow on hard surfaces such as rocks, piers or old shells. Too much rain lowers the salinity, while drought makes water too salty. Both situations can create conditions in which oysters can become vulnerable to disease or unable to reproduce as well.Before the 1880s, the oyster population was so healthy it could filter in a week a volume of water equal to that of the entire bay — about 19 trillion gallons — according to the bay foundation. But now it would take the vastly smaller oyster population more than a year to do the same amount.This fall, biologists in Maryland collected more than 300 oyster samples from the bay and tributaries, including the Potomac River, for their annual survey. The results were promising, experts said, given that 2023 was an unusual year for oysters because drought conditions raised the salinity in the bay.There are several other encouraging signs, experts said. The mortality rate of oysters has stabilized, their “biomass index,” which shows how oyster populations are doing over time, has been increasing for the past 14 years, and an analysis of their habitat showed continued improvements.“They’ve been hit by a pretty severe drought, then got pretty decimated by disease,” Fegley said. “They’ve been cycling back, and we’re now in a state of grace.”Another sign oysters are doing better is their “spat sets” — the process of the tiny larvae (spat) attaching to a hard surface so they can grow into mature oysters. A high number of spat equals successful reproduction. A low number means there are fewer young oysters that will grow into adults.Fegley said last year, the bay’s oysters had “epic, generational spat sets.”“Not only were there a lot of young oysters, which is a good sign of health, but they were distributed through the bay in a way that we had not seen in many years where they were farther up tributaries,” Fegley said. “We’ve had years where the conditions in the bay were just right — with a good balance of salinity levels, no disease and good reproduction.”The success of oysters is also due in part to Maryland and Virginia working over the past few years to build more oyster reefs along the bottom of the bay so oysters could grow successfully, according to Allison Colden, executive director of Maryland for the Chesapeake Bay Foundation. In recent years, she said, more than 1,300 acres of oyster reefs have been replenished in both states.In the past decade, Virginia has also tried to boost its oyster population with aquaculture farms that raise oysters in cages and return their spat to natural waters. The commonwealth increased its number of oyster farms to more than 130 in 2018, up from 60 in 2013, according to the U.S. Department of Agriculture.Last season, Virginia harvested 700,000 bushels of oysters, one of the highest annual harvests since the late 1980s, according to Adam Kenyon, chief of the shellfish management division at the Virginia Marine Resources Commission.Those efforts, plus Mother Nature, have helped create the delicate combination oysters need to survive.“In the last five years, we’ve seen a rebound,” Colden said. “Reproduction has been higher than the long-term average, and we’re seeing more consistency in how they’re doing year-to-year, and that’s a positive sign.”For Jeff Harrison, a fifth-generation waterman who serves as president of the Talbot County Watermen Association, the changes have been like a roller coaster over the 47 years he has made a living off the bay. He’s seen diseases hit, oyster-harvesting seasons shortened, prices fluctuate and many other watermen leave the business because they couldn’t turn a profit.“I’ve seen some of the worst seasons in oystering,” he said. “We’d always have ups and downs. Now we’re seeing a steady up, and we’re hoping we have turned the corner.”
The Maryland mollusks have survived decades of overharvesting, disease and drought.
For the fifth year in a row, the oyster population in the Chesapeake Bay is doing well after decades of combating drought, disease, loss of habitat and overharvesting.
The Maryland Department of Natural Resources said in March that its annual fall oyster survey showed that the “spatfall intensity index” — a measure of how well oysters reproduced and their potential population growth — again hit above a 40-year median.
“We seem to be making some headway,” said Lynn Waller Fegley, director of fishing and boating services for the Maryland Department of Natural Resources. “With the work we’ve done to help restore oysters, and combined with the fact that we’ve been gifted with some really favorable environmental conditions, we’ve seen the oyster population trend upward.”
Oyster-processing companies, oystermen, conservation groups and local fish and wildlife departments in the region have spent years trying to boost the population of oysters, which serve an important role as “filter feeders,” sifting sediment and pollutants such as nitrogen out of the water.
The cleaner water in turn spurs underwater grasses to grow, while oyster reefs create habitats for fish, crabs and dozens of other species. Adult oysters can filter up to two gallons of water per hour, making them the bay’s “most effective water filtration system,” according to experts at the Chesapeake Bay Foundation, a nonprofit organization that advocates for the health of the bay.
Oysters thrive in brackish water — a mix of saltwater and freshwater. They attach and grow on hard surfaces such as rocks, piers or old shells. Too much rain lowers the salinity, while drought makes water too salty. Both situations can create conditions in which oysters can become vulnerable to disease or unable to reproduce as well.
Before the 1880s, the oyster population was so healthy it could filter in a week a volume of water equal to that of the entire bay — about 19 trillion gallons — according to the bay foundation. But now it would take the vastly smaller oyster population more than a year to do the same amount.
This fall, biologists in Maryland collected more than 300 oyster samples from the bay and tributaries, including the Potomac River, for their annual survey. The results were promising, experts said, given that 2023 was an unusual year for oysters because drought conditions raised the salinity in the bay.
There are several other encouraging signs, experts said. The mortality rate of oysters has stabilized, their “biomass index,” which shows how oyster populations are doing over time, has been increasing for the past 14 years, and an analysis of their habitat showed continued improvements.
“They’ve been hit by a pretty severe drought, then got pretty decimated by disease,” Fegley said. “They’ve been cycling back, and we’re now in a state of grace.”
Another sign oysters are doing better is their “spat sets” — the process of the tiny larvae (spat) attaching to a hard surface so they can grow into mature oysters. A high number of spat equals successful reproduction. A low number means there are fewer young oysters that will grow into adults.
Fegley said last year, the bay’s oysters had “epic, generational spat sets.”
“Not only were there a lot of young oysters, which is a good sign of health, but they were distributed through the bay in a way that we had not seen in many years where they were farther up tributaries,” Fegley said. “We’ve had years where the conditions in the bay were just right — with a good balance of salinity levels, no disease and good reproduction.”
The success of oysters is also due in part to Maryland and Virginia working over the past few years to build more oyster reefs along the bottom of the bay so oysters could grow successfully, according to Allison Colden, executive director of Maryland for the Chesapeake Bay Foundation. In recent years, she said, more than 1,300 acres of oyster reefs have been replenished in both states.
In the past decade, Virginia has also tried to boost its oyster population with aquaculture farms that raise oysters in cages and return their spat to natural waters. The commonwealth increased its number of oyster farms to more than 130 in 2018, up from 60 in 2013, according to the U.S. Department of Agriculture.
Last season, Virginia harvested 700,000 bushels of oysters, one of the highest annual harvests since the late 1980s, according to Adam Kenyon, chief of the shellfish management division at the Virginia Marine Resources Commission.
Those efforts, plus Mother Nature, have helped create the delicate combination oysters need to survive.
“In the last five years, we’ve seen a rebound,” Colden said. “Reproduction has been higher than the long-term average, and we’re seeing more consistency in how they’re doing year-to-year, and that’s a positive sign.”
For Jeff Harrison, a fifth-generation waterman who serves as president of the Talbot County Watermen Association, the changes have been like a roller coaster over the 47 years he has made a living off the bay. He’s seen diseases hit, oyster-harvesting seasons shortened, prices fluctuate and many other watermen leave the business because they couldn’t turn a profit.
“I’ve seen some of the worst seasons in oystering,” he said. “We’d always have ups and downs. Now we’re seeing a steady up, and we’re hoping we have turned the corner.”