RD615 - The 2019 Virginia Blue Crab Fishery Management Plan
The 30th Bay-wide Winter Dredge Survey was conducted from December 2018 to March 2019 by the Virginia Institute of Marine Science and Maryland Department of Natural Resources. Results indicate the blue crab stock is not depleted and overfishing is not occurring (Table 1). Table 2 presents data from the survey since the 2011 Benchmark Stock Assessment. The 2018-2019 Winter Dredge Survey estimate of abundance of all size classes of blue crabs is 594 million crabs, which is 60% higher than the 2017-18 total abundance estimate of 372 million crabs and 41% higher than the long-term survey average.
Juvenile crabs accounted for 54.4% of the 2018-19 total abundance, numbering 324 million crabs. This is nearly double the 2017-18 juvenile population of 167 million crabs and 44% higher than the long-term survey average of 224 million juvenile crabs. 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 191 million overwintering female crabs that could potentially spawn in 2019 (if not harvested prior to the spawning seasons), which is the fifth highest amount of spawning-age female crabs determined by this survey and 70% above the long term average. The 2019 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 but below the target of 215 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 since 2008. That conservation measure may partially account for above average spawning-age female abundance in eight of the eleven years since the winter dredge season was closed because it allows juvenile crabs from the previous year 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.
Year-to-year variation in abundance of blue crabs can be expected due to environmental influences, especially during the early life stages of crabs. 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 have an effect on all life stages of the crab population. 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. Overall overwintering mortality of 1.8% in 2019 was well below the survey average and was the second lowest mortality rate since 2014. 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).
The Chesapeake Bay jurisdictions have also relied on a management framework enacted in 2014 in which the fishery is regulated 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 have paid close attention the current year’s juvenile abundance, as well as the mature female abundance, as the juveniles are the subsequent year’s spawning stock. Six years ago (2013-14), the low abundance of spawning-age female crabs (68.5 million) indicated a depleted stock, as an abundance below the threshold of 70 million spawning-age female crabs is considered depleted. In 2019, the abundance of juvenile crabs at 324 million was 44% higher than the long-term survey average. 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. Predation and harvest in late summer and fall of 2019 will determine how many juveniles will mature as spawning-age female crabs in 2020 and join the mature female crabs that were not exploited by fisheries in 2019. For 2019 and 2020, the Commission reestablished the traditional crab pot season: a March 17 opening and a November 30 closure. Additional crab conservation measures maintained since 2014 include a shorter harvest season closure for all other crab gear that exploits juvenile (peeler-size) crabs.
The VMRC, PRFC (Potomac River Fisheries Commission), and MD DNR (Maryland Department of Natural Resources) agreed that any liberalization of current management measures concerning the blue crab fisheries must not interfere with the stability of the stock or annual Bay-wide abundances near the 215 million spawning-age female crab target. In response to the 2018-19 Winter Dredge Survey results, the jurisdictions agreed to maintain the current cautious, risk-averse approach in the 2019 season and to focus on the sustainability of the fishery. 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 and vessel limits. This year, the Commission decided against substantive increases in harvest, but increased November bushel limits at the request of the Crab Management Advisory Committee because the projected increase in annual harvest was only 0.5%. The Commission maintained the reduced bushel limits for March of 2020.