RD702 - The 2021 Virginia Blue Crab Fishery Management Plan
The 32nd Bay-wide Winter Dredge Survey was conducted from December 2020 to March 2021 by the Virginia Institute of Marine Science (VIMS) and Maryland Department of Natural Resources (MD DNR). Results indicate the blue crab stock is not depleted and overfishing is not occurring. The 2020-21 Winter Dredge Survey estimate of abundance of all size classes of blue crabs is 282 million crabs, which is 33% lower than the long-term survey average of 421 million crabs and 30% lower than the 2019-20 total abundance estimate of 405 million crabs.
Juvenile crabs accounted for 30% of the 2020-21 total abundance, or 86 million crabs. This is 54% lower than the 2019-20 juvenile population of 185 million crabs and 61% lower than the long-term survey average of 219 million juvenile crabs. It is also the lowest juvenile abundance recorded in the 32 years of the Winter Dredge Survey. Juvenile crabs surveyed in wintertime are important to the current year’s harvest, as they recruit to harvestable size in late summer and fall and contribute to the following year’s late May and July-August spawning periods.
The survey estimated 158 million overwintering female crabs that could potentially spawn in 2021 (if not harvested prior to the spawning seasons), which is 4% above the average since female-conservative measures were put in place in 2008 and 36% above the long term average. The 2021 abundance estimate of spawning-age female crabs is well above the threshold of 70 million crabs established by the 2011 Chesapeake Bay Blue Crab Stock Assessment (CBSAC) but below the target of 196 million crabs. Since 2008, there has generally been a continuation of management measures by all Chesapeake Bay jurisdictions to conserve the spawning-age female crabs. The Virginia winter dredge fishery season has been closed each year since 2008. That conservation measure may partially account for above average spawning-age female abundance in eight of the twelve years because closing the winter dredge season allows juvenile crabs to be free of fishing pressure after they mature in fall. The importance of the mature female crabs is their contribution to the spawning events in late May and July-August of the same year the Bay-wide Winter Dredge Survey is completed. These crabs are also important to the spring and early summer harvest, as a high proportion of the Virginia commercial and recreational harvests consists of female crabs.
Conservative management can lessen the effects of annual variation, but year-to-year variation in blue crab abundance is expected due to environmental influences, especially during the early life stages of crabs when natural mortality is high. Conservation of female spawning-age crabs as well as juvenile crabs is the primary management objective to attempt to lessen variability of the blue crab stock abundance. The extensive management measures from 2008 that were implemented throughout the Chesapeake Bay jurisdictions have helped to mitigate year-to-year variability in the fisheries that previously resulted in overfishing during many prior years (see Attachment 1). Juvenile crab abundance can vary because of inter-annual differences in the entrainment of crab larvae from the ocean to Chesapeake Bay. This process is subject to natural fluctuations in the prevailing current and wind patterns. Environmental factors including weather conditions and predation can influence all life stages of the crab population. Cold temperatures in particular decrease survival. Due to a mild winter, overall overwintering mortality was 2.8% in 2021, which is higher than in the previous two winters but below the 1996-2021 average of 4.46%. Additionally, year to year variation of predators, such as red drum, blue catfish, striped bass, and adult blue crabs, can affect juvenile blue crab abundance.
The Chesapeake Bay jurisdictions have relied on a management framework enacted in 2014 in which the fishery is regulated annually from July 5 through July 4 of the next year. The benefit of this approach is that two Bay-wide Winter Dredge Surveys can be accomplished in that 12-month period, and conservation efforts can be applied after either survey is complete. Since 2014, the Virginia Marine Resources Commission (VMRC) and other Chesapeake jurisdictions (Maryland and the Potomac River Fisheries Commission) have paid close attention to the current year’s juvenile abundance, as well as the mature female abundance, as the juveniles in one year are the subsequent year’s spawning stock. The current July-to-July regulatory framework for blue crabs allows for the conservation of female crabs for spawning in both the current and following year. In 2021, the abundance of juvenile crabs at 86 million was 61% lower than the long-term survey average. This may be cause for concern, but researchers on CBSAC did not recommend any actions be taken to this crabbing season due to the highly variable nature of crab recruitment and juvenile survival. Adult female abundance is above average, which does not yet suggest a downward trend in population. Predation and harvest in late summer and fall of 2021 will determine how many juveniles will mature as spawning-age female crabs in 2022 and join the mature female crabs that were not exploited by fisheries in 2021. Additional crab conservation measures maintained since 2014 include a shorter harvest season closure for all other crab gear that exploits juvenile or peeler-size crabs.
The VMRC, MD DNR, and PRFC (Potomac River Fisheries Commission) agree that any liberalization of current management measures concerning the blue crab fisheries must not interfere with the stability of the stock. In response to the 2020-21 Winter Dredge Survey results, the jurisdictions agreed to maintain the current cautious, risk-averse approach in the 2021 season and to focus on the sustainability of the fishery. They also agreed to closely examine juvenile populations and subsequent adult populations through the MD DNR and VIMS juvenile trawl surveys.
Each year the Commission uses the results of the Winter Dredge Survey to consider potential adjustments to blue crab management measures, such as changes in bushel limits and seasons. At a July 27, 2021 public hearing, the Commission reestablished the traditional crab pot season for 2021 and 2022: a March 17 opening and a November 30 closure.