RD586 - The 2018 Virginia Blue Crab Fishery Management Plan
The 29th Bay-wide Winter Dredge Survey was conducted from December 2017 to March 2018 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 (Attachment 1). Table 2 presents data from the survey since the 2011 Benchmark Stock Assessment. The 2017-2018 Winter Dredge Survey estimate of abundance of all size classes of crabs is 371 million crabs, which is 18.4% lower than the total abundance estimate from the 2016-17 survey of 455 million crabs and 18.3% below the long-term survey average.
The most recent abundance of juvenile crabs enumerated from the winter survey was 168 mil-lion, the tenth lowest number of recruits since 1990 and 33.9% below the long-term survey average of 254 million juvenile crabs. However, 2017-18 juvenile crab abundance was nearly 34% above survey results from 2016-17. The importance of the juvenile crabs surveyed in wintertime is their contribution to the current year’s late summer and fall harvest when they have recruited to harvestable size and their contribution to the subsequent year’s late May and July-August spawning periods.
The estimate of overwintering female crabs that could potentially spawn (if not harvested prior to the spawning seasons) in 2018 was 147 million, the ninth highest amount of spawning-age female crabs determined by this survey and 19% above the long term average. 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 also are 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 as a result of the effects of 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 the Virginia portion of Chesapeake Bay. This process is subject to natural fluctuations in the prevailing cur-rent 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.
Since 2008, there has generally been a continuation of management measures by all Chesapeake Bay jurisdictions to conserve the spawning-age female crabs. The number of spawning-age female crabs, estimated in 2018 as 147 million, decreased 42% from the survey high 2017 estimate of 254 million. The 2018 abundance estimate of spawning-age female crabs is still 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. The Virginia winter dredge fishery season has been closed since 2008. That conservation measure may partially account for above average spawning-age female abundance the past three years, and allowed the juvenile crabs from the previous year to be free of fishing pressure after they matured in fall.
Overwintering mortality in 2018 was slightly higher than average but well below the highest values of the Bay-wide Winter Dredge Survey time series (1996, 2003, and 2015). 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 over-fishing during many years (see Attachment 1).
The Chesapeake Bay jurisdictions have also relied on a new management framework for the past four seasons 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 no longer manage only the spawning-age female crabs but pay close attention the current year’s juvenile abundance, as the juveniles are the subsequent year’s spawning stock.
Just five years ago (2013-14), the low abundance (68.5 million) of spawning-age female crabs indicated a depleted stock, as an abundance below the threshold of 70 million spawning-age female crabs is considered depleted. In 2018, the abundance of juvenile crabs is still below the long-term survey average at 168 million. Predation and harvest in late summer and fall 2018 will determine how many of these juveniles will mature as spawning-age female crabs in 2019 and join the mature female crabs that were not exploited by fisheries in 2018.
The VMRC, PRFC (Potomac River Fisheries Commission) and MD DNR (Maryland Department of Natural Resources) agree that any liberalization of current management measures concerning the blue crab fisheries must not interfere with the stability of the stock and of annual Bay-wide abundances near the 215 million spawning-age female crab target. In response to the 2018 Winter Dredge Survey results, the jurisdictions agreed to maintain the current cautious, risk-averse approach in the 2018 season and to focus on the sustainability of the fishery. No substantive adjustments were made to the management of the fishery.
For 2018 and 2019, the Commission reestablished the traditional crab pot season: a March 17 opening and a November 30 closure. Previously, there had been a December 20 closure in 2016 and a March 1 opening of the season in 2017. The recent shift to a July-to-July crab regulatory framework allows for the conservation of female blue crabs for spawning in the summer of the cur-rent year and for the conservation of a portion of the spawning-age and juvenile female crabs for the next year’s spawn. The Commission also maintained the reduced wintertime bushel limits for November of 2018 and March of 2019 that were implemented the previous year.
In Virginia, additional crab conservation measures maintained since 2014 include reduced crab pot bushel and vessel possession limits for specific time periods and a shorter harvest season closure for all other crab gear that exploits juvenile (peeler-size) crabs. Each year the Commission can adjust measures based on results of the Bay-wide Winter Crab Dredge Survey, while depending on the bushel and vessel limits already in place to buffer inter-annual variability in spawning-age female abundance and juvenile crab production.