Recent Progress: Decrease
Between 2021 and 2022, the abundance of adult (age 1+) female blue crabs in the Chesapeake Bay decreased 39% from 158 million to 97 million. This number is lower than the target of 196 million, but above the 72.5 million threshold that is considered to be the minimum sustainable level for female blue crabs in the Bay. Although it is well known that blue crab populations exhibit natural annual variability due to their biology and other environmental factors such as temperature, coastal currents, weather patterns, and predation, the Chesapeake Bay Stock Assessment Committee (CBSAC) is interested in better understanding how these factors drive blue crab population dynamics. CBSAC is in the process of identifying the key drivers to be addressed and will discuss how these factors might be incorporated into future stock assessments at a workshop in September 2022.
Outlook: On Course
The adult female blue crab abundance has not fallen below the threshold since 2014, indicating that the population is sustainable. In addition, the female exploitation rate has not fallen below the threshold since 2008, which suggests that management has been effective. The Blue Crab Abundance Outcome is on course and is expected to be met by 2025.
Since data collection began in 1990, the abundance of adult female blue crabs has peaked three times: first in 1991 when abundance reached 227 million, second in 2010 when abundance reached 246 million and third in 2017 when abundance reached a record-high 254 million. Since female-specific regulations were implemented in 2008, the average adult female blue crab abundance has doubled from the previous decade. In the last few years, however, the abundance of mature females has declined. The 2022 estimate is the lowest since 2014, when female abundance fell below the management threshold (then 70 million adult females).
In November 2020, the three jurisdictions (Maryland, Virginia, and the Potomac River Fisheries Commission [PFRC]) formally adopted new female-specific reference points generated by the 2017 blue crab stock assessment update, which included more recent survey and harvest data. The threshold abundance of 70 million mature adult female crabs (age 1+) increased to 72.5 million, and the target abundance of 215 million adult females decreased to 196 million, based on the best available science.
Blue crabs support commercial and recreational fisheries across the region. The female-specific reference points associated with this outcome were recommended in the 2011 blue crab benchmark stock assessment and adopted by Maryland, Virginia and PRFC in 2012 and were updated at the 2017 blue crab stock assessment update. Where annual adult female blue crab abundance falls in relation to these numbers informs management decisions for the blue crab fishery.
Anthropogenic activity—including harvest pressure and development that leads to the loss of fish and shellfish habitat—can affect blue crab populations. Environmental factors—including water temperatures, coastal currents, weather patterns and natural predation—can also affect blue crab abundance. Water quality improvements, underwater grass restoration and proper harvest management will be critical to maintaining this valuable resource.
To achieve this outcome, Chesapeake Bay Program partners have committed to:
- Assessing blue crab stock status and communicating the results to managers and the public.
- Evaluating and improving the effectiveness of the blue crab stock assessment model.
- Identifying and addressing priority blue crab science needs.
Monitoring and assessing progress toward the outcome will occur through the Chesapeake Bay Stock Assessment Committee’s (CBSAC) annual review of blue crab survey data and determination of population status relative to biological reference points. The continuation of the annual Bay-wide Blue Crab Winter Dredge Survey will be essential in estimating the blue crab population and monitoring the stock.
As part of the Chesapeake Bay Program's partnership-wide implementation of adaptive management, progress toward this outcome was reviewed and discussed by the Management Board in November of 2021. It will be reviewed and discussed by the Management Board again in November 2023.
Logic & Action Plan
Participating partners have committed to taking a series of specific actions that will support the management strategy listed above.
The Sustainable Fisheries Goal Implementation Team leads the effort to achieve this outcome.
Participating partners include:
- Maryland Department of Natural Resources (State of Maryland)
- University of Maryland Center for Environmental Science Chesapeake Biological Laboratory (State of Maryland)
- Virginia Institute of Marine Science (Commonwealth of Virginia)
- Virginia Marine Resources Commission (Commonwealth of Virginia)
- Potomac River Fisheries Commission
- National Marine Fisheries Service (National Oceanic and Atmospheric Administration)
- University of North Florida