Chesapeake Bay Blue Crab Survey for Winter 2016 Shows 35-percent Increase in Overall Population Over 2015

On April 12, 2016, the Virginia Marine Resources Commission (VMRC), the Maryland Department of Natural Resources (Md. DNR), and the Virginia Institute of Marine Science (VIMS) reported the results of the latest winter dredge survey of Blue Crab populations in the Chesapeake Bay.  Since 1990, the survey has been conducted each year from December to March by VIMS and the Md. DNR.  The report for the 2016 survey showed increases over the previous year in overall Bay-wide crab abundance and in certain age categories.  Following is an excerpt from the VMRC’s April 12 news release on the 2016 survey (see Sources, below, for the Internet link to the news release).

“The results of the 2016 Blue Crab Winter Dredge Survey show the total population of blue crabs in the Chesapeake Bay climbed 35 percent to a total of 553 million.  This is the fourth highest level in two decades, since 1996, and builds on last year’s 38 percent boost in abundance. … The spawning female stock almost doubled, from 101 million to 194 million, while the adult male stock more than doubled, from 44 million to 91 million.   These are the second highest levels recorded since 1995 and bode well for a good crab harvest this year.  Still, this level of spawning-age female crabs remains below the scientifically recommended target of 215 million but well above the minimum safe threshold of 70 million crabs.  The juvenile abundance increased only slightly, from 269 million to 271 million, which is just above the average level of juveniles recorded over the past almost 30 years.   The bay-wide crab harvest last year increased by 42 percent, to 50 million pounds.

“…Crab spawning naturally fluctuates and can be affected by wind, currents, weather, cannibalism and increased predation on crabs by other species.  In recent years, unexpected predation events and stressful combinations of environmental factors have caused dramatic downturns in crab stock abundance.  This highlights the need for fishery managers to continue to enhance resilience of the stock through adaptive management to compensate for unusual or extreme environmental conditions.  A bay-wide 10 percent crab harvest reduction enacted in 2014 by VMRC, Maryland, and the Potomac River Fisheries Commission to combat low overall crab abundance and to boost a dangerously depleted female spawning stock appears to have been effective.

“…The annual Bay-wide Winter Dredge Survey is the primary assessment of the Bay’s blue crab population, and has been conducted annually by the Virginia Institute of Marine Science and Maryland’s Department of Natural Resources since 1990.  The survey employs crab dredges to sample blue crabs at 1,500 sites throughout the Chesapeake Bay from December through March.  Sampling during winter when blue crabs are usually buried in the mud and stationary, allows scientists to develop, with good precision, estimates of the number of crabs present in the Bay.”

Following are the lowest and highest estimates of key parts of the Bay crab population since 1990:
Total (both sexes and all ages) – low of 251 million in 2007; high of 852 million in 1993.
Spawning-age females – low of 53 million in 1999; high of 246 million in 2010.
Juvenile-age (both sexes): low of 105 million in 1992; high of 581 million in 2012.
Bay-wide commercial harvest – low of 35 million in 2014; high of 107 million in 1993.

A table of all the results since 1990 is available in the VMRC’s April 12, 2016, news release (see link below).

Sources:
Scientific Survey Shows Solid Blue Crab Stock Improvement (PDF), Virginia Marine Resources Commission News Release, 4/12/16.
Bay’s crab population hits four-year high, survey finds, Bay Journal, 4/12/16.
Blue crab population increase could lead to looser regulations, [Annapolis, Md.] Capital Gazette, 4/12/16.

For previous News Grouper items on the Blue Crab winter dredge survey, please see this link: https://vawatercentralnewsgrouper.wordpress.com/?s=blue+crab+winter+dredge+survey.

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