A female blue crab with an acoustic telemetry tag on its shell. Scientists at the Smithsonian Environmental Research Center use telemetry tags to track the migration of blue crabs throughout the Chesapeake. SERC Fisheries Conservation Lab Life isn’t exactly easy for a young blue crab in the Chesapeake Bay. For one, the crustaceans must dodge predators—they have to avoid invasive blue catfish and even thwart cannibalism by their elders. But these threats alone can’t explain a long-term drop in population that the crabs have seen over the past decade and a half.
According to a recent 282-page draft report, the bay’s juvenile blue crabs declined by 50 percent from 2010 to 2023—and the reason is eluding scientists. The findings are still being finalized, but the main ideas were presented at a meeting of the Chesapeake Bay Commission this month.
“It’s concerning, because there should be enough female crabs to produce more juveniles than we saw from 2020 to 2024,” Matthew Ogburn, an ecologist at the Smithsonian Environmental Research Center who worked on the report, tells Smithsonian magazine. “This implies that there’s something affecting baby crabs that we haven’t accounted for yet.”
Blue crabs hatch as microscopic larvae, then get carried out toward the Atlantic Ocean on currents. After a few weeks of growing, they come back into the bay and hide amid grasses and marshes to develop into juveniles. At the start of their juvenile phase, the crabs are just one-fifth of an inch long, and after several molts, they’ll become adults, if they can survive.
The issue with the crab population, the report broadly states, is that young crabs are not surviving into reproductive adulthood, a problem known as poor “recruitment,” per the Bay Journal’s Timothy B. Wheeler and Jeremy Cox. But researchers can’t completely explain why that’s happening.
“There’s no smoking gun,” Rom Lipcius, a fisheries scientist with the Virginia Institute of Marine Science who worked on the assessment, tells the Bay Journal.
As of last year, the Chesapeake’s juvenile blue crabs had seen six consecutive years of below-average numbers estimated during the annual winter dredge survey, which looks for crabs buried in the bay’s sediment during the colder months, when they don’t move much and are easier to count. The total winter crab population in 2022 hit the lowest number on record since monitoring began in 1990.
Last week, however, experts released the results of the 2026 winter dredge survey, which brought some good news for the bay’s juvenile crabs. The count revealed an increase in the total number of blue crabs, despite the total population still sitting below average. Juvenile blue crabs and adult males were also up, though the survey found a drop in adult females.
Specifically, the survey estimated 349 million blue crabs were in the Chesapeake Bay, which is a 46 percent increase from last year. The juveniles saw a sharp jump in population compared to 2025—their numbers this winter were around 228 million, which is a 121 percent increase. This represents the highest estimated total of juveniles since 2019.
“It’s very encouraging to see higher levels of blue crabs and juveniles, especially after a few years of lower juvenile recruitment,” Mandy Bromilow, the blue crab program manager for Maryland’s Department of Natural Resources, says in a statement. “However, we’ll still have to remain vigilant about the population, given that we have seen declines since 2011.” It also remains to be seen whether the high number of juveniles counted this winter can survive into the summer and fall.
To Ogburn, the more significant finding from last week’s report is the drop in female crabs. “The number of females fell to the lowest level since 2014, close to the minimum threshold for maintaining a sustainable fishery,” he says. “Although juvenile numbers receive a lot of attention, there is much more confidence in the female abundance numbers … and fisheries management is primarily based on the females.”
While the bump in juvenile crab numbers is promising, it doesn’t yet negate the long-term trend. The decline of juvenile blue crabs found in the assessment report didn’t come as a surprise; scientists were aware that the population had dropped. The bigger question is why.
No one factor strongly explains the population loss of juveniles. Invasive blue catfish, which some might have expected to be at fault, are only responsible for 8 percent of the decline, the new report revealed. And low oxygen zones in the bay, caused by nutrient pollution from sources like fertilizer and manure, had no detectable effect on juvenile crab numbers.
The team also ruled out cannibalism by adult crabs. In a study earlier this year, a team led by the Smithsonian Environmental Research Center found evidence of adult crabs eating juveniles. But the level of cannibalism hasn’t changed significantly of late, Ogburn notes.
“Given that numbers of adult crabs have been low to moderate in recent years, they’ve had less impact on juvenile populations than they can in years when populations of adults are high,” he says. Other predators, such as red drum and striped bass, could play a role, but scientists aren’t sure.
Another possible culprit is environmental change, since the young crabs are reliant on currents to move around—and those currents are driven by rain, wind and tides. Ogburn suggests that shifting weather patterns could have a hand in the downward trend, but he emphasizes that more research is required to know for sure. NOAA is leading a study that’s investigating this idea, but “it’s too early to say,” Ogburn notes, as they’re only in year two of the three-year project.
“I think the idea that there’s a single cause is one that’s probably not true,” Mike Wilberg, a fisheries scientist at the University of Maryland Center for Environmental Science, says to the Virginia Mercury’s Shannon Heckt. “There’s probably always multiple factors affecting crabs, as well as all the other species in the bay. And so it’s really difficult to disentangle them.”
Blue crabs were plentiful in the largely brackish waters of the Chesapeake Bay in the 1970s and 1980s, leading to strong crab yields for fisheries. But this boom was followed by a period of lower numbers of crabs—especially females—and overharvesting between the mid-1990s and 2007, Ogburn says. Fishery management agencies in Maryland and Virginia added restrictions on crab harvests, reducing the harvest of females by 34 percent.
“This has resulted in increased populations and harvests on average, although the target crab population has only been achieved a few times,” Ogburn says. “The population and fishery are in a much better place than the mid-1990s to 2007, but still not as good as what we’d like.”
Female blue crabs lay egg masses that contain two million eggs on average—and as many as eight million.
