Robert Schilling holds a female blue crab with a visible "sponge" made of about two million eggs on board a deadrise workboat near Deal Island, Md., on May 26, 2020. (Image by Will Parson/Chesapeake Bay Program)

The 2021 Blue Crab Advisory Report was released today, sharing the good news that the Chesapeake Bay’s blue crab population is still considered to be healthy—not being overfished or depleted. This statement is based on a series of biological reference points set by the Chesapeake Bay Stock Assessment Committee (CBSAC), a group of experts from federal and state agencies, and academic institutions from around the Chesapeake Bay watershed.

Biological reference points determine what the safe level for harvesting blue crabs would be, to ensure their population remains healthy. This information is determined by the annual Bay-wide Winter Blue Crab Dredge Survey, as well as harvest data from the prior year. For the past several years, the CBSAC had used reference points from 2011 to determine the target and threshold levels for the Chesapeake Bay female blue crab population. The target is the level that we want to achieve and maintain—it means that female blue crabs are considered to be stable and sustainable. On the other hand, if the female blue crab population falls below the threshold level, then they are considered to be in trouble, and regulations will be put into place to limit harvesting until their numbers rebound. As long as the current population of female blue crabs fall in-between the target and the threshold levels, they are considered to be at a healthy number, although some restrictions will be in place to ensure they remain there.

Just last year, the CBSAC decided to begin using more recent survey and harvest information from a stock assessment update that had been conducted in 2017. This definitely is good news, as the reference points increased to a new target of 196 million and a new threshold of 72.5 million, which indicates the female blue crab population continues to be healthy and had improved enough since 2011 to increase these levels

In 2021, the winter dredge survey found that the population of female blue crabs had increased to 158 million from 141 million in 2020. Approximately 19% of all female blue crabs in the Bay were harvested in 2020.

While this year’s population of female blue crabs is considered healthy, the overall blue crab population in the Bay (including males and juveniles) is low and reflects a declining pattern over the past two years. The overall population fell from 405 million in 2020 to 282 million in 2021. The population of male blue crabs (ages 1+) was estimated to be 39 million in 2021, down from 79 million in 2020. More regulations are in place to protect females since they are the ones producing the next generation of crabs.

Commercial anglers harvested approximately 41.6 million pounds of blue crabs from the Chesapeake Bay and its tributaries in 2020, which was a decrease from the 61 million pounds harvested in 2019. It is estimated that recreational crabbers caught 2.4 million pounds in 2020, also a decrease from 2019, when they harvested approximately 3.8 million pounds.

What experts are really keeping an eye on this summer is the population of juvenile blue crabs. These are the crabs that will grow to a harvestable size by next year. Their population declined in 2021 to 86 million from 185 million in 2020. This is the second year in a row that their population has declined, and the current numbers estimated in the Bay fall below their long-term average of 224 million.

The 2021 Blue Crab Advisory Report recommends that researchers explore environmental factors that may contribute to the highly variable nature of the blue crab population, as well as implement programs to track the recreational and commercial harvest more accurately.

The population of blue crabs do vary from year-to-year depending on weather conditions and the previous year’s harvest. However, another factor that causes the population of blue crabs to fluctuate is habitat loss. Blue crabs use underwater grasses as nurseries and feeding grounds. When there is a loss in underwater grass acreage—often due to weather conditions, climate change and pollution—the blue crab population will also decline. In 2019, preliminary data showed 66,387 acres of underwater grasses in the Bay—a 17% decline from the previous year.

Want to ensure your summertime backyard picnic continues to feature Chesapeake blue crabs? You can take actions that reduce pollution that may flow into the Bay (and your own drinking water) and that help combat climate change.

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Chesapeake Program

That is a great question, Earl. Female blue crabs have a greater impact on the number of crabs that will be in the Bay the next year than juveniles and males do, especially since juveniles cannot be harvested. As long as the current population of female blue crabs fall in-between the target and the threshold levels, they are considered to be at a healthy number.

Earl Bradley

Doesn't' the drastic reduction of the number of juvenile crabs and the overall population of crabs in spite of the adequate number of female crabs indicate that the size of the commercial harvest be reduced?

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