Blue Crab Abundance
Maintain a sustainable blue crab population based on a target of 196* million adult females. Refine population targets through 2025 based on best available science.
*The original target of 215 million was revised in November 2020 based on the best available science as outlined in the outcome language.
Progress
Recent Progress: Increase
Between 2022 and 2023, the abundance of adult (age 1+) female blue crabs in the Chesapeake Bay increased 57% from 97 million to 152 million. This number is lower than the target of 196 million, but well 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, with the recent low abundances, the Chesapeake Bay Stock Assessment Committee (CBSAC) has made it a priority to better understand the factors that drive blue crab population dynamics (i.e., abundance, recruitment and mortality) in the Chesapeake Bay. In September 2022, CBSAC held a Blue Crab Science Workshop in which CBSAC members and other experts discussed factors of interest including habitat availability (e.g., submerged aquatic vegetation, marsh), predation (e.g., red drum, blue catfish), food availability (e.g., clams), environmental conditions (e.g., water temperature, dissolved salt levels, depleted oxygen), oceanic conditions (e.g., wind and tidal currents), and disease. Participants identified data and analytical needs surrounding these factors. CBSAC will continue to prioritize understanding how these factors impact the blue crab population in the Chesapeake Bay.
Outlook: On Course
The adult female blue crab abundance has not fallen below the minimum sustainable level for female blue crabs since 2014, indicating that the population is sustainable. In addition, the female exploitation rate has not risen above the established sustainability 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.
Adult Female Blue Crab Abundance (1990-2023)
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.
Management Strategy
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.
Ongoing
- Assessing blue crab stock status and communicating the results to managers and the public.
- Analyzing the results of the annual Bay-wide Blue Crab Winter Dredge Survey.
- Developing management recommendations and deliver an advisory report.
- Developing decision criteria to determine the timing of blue crab stock assessment updates.
- Evaluating and improving the effectiveness of the blue crab stock assessment model.
- Improving understanding of catchability and gear effects on blue crab abundance estimates.
- Improving harvest reporting and characterization of catch composition.
- Evaluating blue crab indices and analytical models to ensure that the best approaches are used for stock assessment, including updates to the management reference points.
- Developing a blue crab population simulation model to test stock assessment model assumptions.
- Planning a benchmark stock assessment.
- Identifying and addressing high priority blue crab science needs.
- Conducting research that examines relationships between, and primary drivers of, blue crab abundance, recruitment and other important aspects of population dynamics.
- Sharing results with relevant stakeholders and interested parties.
Recently Completed
2022
- Held a Blue Crab Science Workshop to discuss science needs and data gaps related to blue crab population drivers and stock assessment
2021
- Developed the Blue Crab Harvest Reporting document (2021)
Participating Partners
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, William & Mary (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
- Patuxent Environmental and Aquatic Research Laboratory, Morgan State University
Maryland, Virginia and PRFC also engage commercial and recreational blue crab harvesters through committees and advisory groups, which include the Maryland Blue Crab Industry Advisory Committee, Maryland Tidal Fisheries Advisory Commission, Maryland Watermen’s Association, Virginia Crab Management Advisory Committee, Virginia Watermen’s Association, and the Potomac River Crab Advisory Committee.