Every winter, Maryland and Virginia biologists ample 1,500 spots around the Chesapeake
to learn how the Bay’s blue crabs are doing.
Taken at a time when crabs are dormant, the
“winter dredge survey” is a reliable snapshot
of the population. The results show signs
of recovery in recent years and teach other
lessons as well.
Anyone who crabs knows how poor the fishery was from the early 1990s to the late 2000s.
Many recreational crabbers just stopped going
out. Some theorize that the big oyster die-off
in the mid-1980s forced watermen to crab a
lot harder and put too much pressure on the
population. Scientists had said that blue crabs
were hard to overfish because they produce a
lot of eggs. The dredge survey, which began
in 1990, helped us determine that even the
fecund crab has its limits.
In 2008, the repeated poor outlook from
the survey convinced politicians to endorse
a new science-based way to manage the
fishery. The number of mature female crabs
would be maintained above a minimum
“threshold” level to ensure enough young
crabs were produced each year. At first,
watermen didn’t like the new restrictions on
their crabbing, but they soon accepted the
wisdom of this strategy.
After the crab population doubled two years
later, most people were convinced. But then
it dropped off as quickly as it had risen.
Scientists, watermen, and CBF theorized the
drop was due to rockfish and drum eating
the baby crabs. With protective underwa-
ter grasses reduced to about 20 percent of
historic coverage leaving crabs exposed, the
theory made sense. If so, the clear message
is that it’s not enough just to maintain min-
imum numbers of spawning crabs, we also
need to maintain their habitat.
We are seeing a welcome new rise in crab
numbers in the two most recent surveys. In
2015, they started to increase, pushing above
the threshold, and this year, they continued
to climb, approaching scientists’ preferred
“target” level. Catch reports this year
confirm the increase, and even recreational
crabbers are back at it. Is it a coincidence
that the Bay’s underwater grasses expanded
last year in response to the clear water that
has persisted into this year? Not likely. The
formula of science-based fishery manage-
ment and improved habitat is working for
crabs and crabbers and will work for other
Bay species as well.
By Bill Goldsborough
CBF Fisheries Director Bill
Goldsborough grew up on the
Eastern Shore and got his
inspiration from fishing the Bay
for rockfish with his father.
1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016
Female Spawning Age Crabs in the Chesapeake Bay (Millions)
Estimated Threshold Target
Source: Winter Dredge Survey and Blue Crab Advisory Report